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Tracing the dynamics of animal excreta N in the soil-plant-atmosphere continuum using 15N enrichment
ARTICLE IN PRESS
Tracing the dynamics of animal excreta N in the soil-plantatmosphere continuum using 15 N enrichment Phillip M. Chalka,∗, Caio T. Ináciob, Deli Chena a
Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC, Australia Embrapa Solos, Rio de Janeiro, Brazil Corresponding author: e-mail address: [email protected]
b ∗
Contents 1. Introduction 2. Production of 15N-enriched animal excreta 2.1 Feeding 15N-enriched plant materials or urea to domestic animals 2.2 Addition of 15N-enriched urea or ammonium to unlabeled animal urine 2.3 Addition of 15N-enriched ammonium, urea, urine or feces to unlabeled animal waste slurries 3. Uniformity of 15N-labeling of excreta 3.1 Within feces 3.2 Within urine 3.3 Between feces and urine 3.4 Within slurry 4. Recovery of 15N-labeled excreta in plants and soil 4.1 Feces 4.2 Urine 4.3 Slurry 5. Relative efficiencies of 15N-labeled excreta and 15N-labeled synthetic fertilizer 6. Interactions between synthetic fertilizer N and animal excreta N 6.1 15N-labeled fertilizer + unlabeled excreta 6.2 15N-labeled excreta + unlabeled fertilizer 7. Losses of N from excreta-amended soils 7.1 As ammonia and nitrous oxide emissions 7.2 As nitrate and ammonium in leachates 8. The residual value of excreta N in crop sequences 9. Partial 15N balance 10. Conclusions Acknowledgments References
Advances in Agronomy ISSN 0065-2113 https://doi.org/10.1016/bs.agron.2019.10.004
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2019 Elsevier Inc. All rights reserved.
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Abstract The increased demand for organic farm products, and the attendant restrictions on the use of synthetic N fertilizers in both traditional and organic agriculture, has focused attention on the efficacy of organic sources of N, including animal excreta. However, questions arise in regard to the agronomic and environmental benefits of excreta as alternative sources of N. These questions are best addressed through the experimental use of 15N-enriched excreta, which enable the labeled source to be unequivocally traced through the soil-plant-atmosphere continuum, which N difference or N equivalence techniques cannot achieve. In contrast to organic and inorganic N compounds that can be purchased commercially with a specified 15N label on the component N moieties, 15N-enriched excreta must be prepared by the investigator. The methods of production and the uniformity of labeling of the components of 15N-enriched excreta (feces, urine) and their admixture (slurry), the N use efficiencies of excreta in crop production, and comparisons and interactions of excreta with synthetic N sources are reviewed. Losses of N from excreta-amended soils to the environment and the residual N value of excreta in crop sequences are also examined. It was concluded that while similar agronomic and environmental issues surround the use of both synthetic fertilizers and excreta as sources of N for plant nutrition, the processes differ in intensity and duration both spatially and temporally.
1. Introduction Intensive crop production worldwide has become reliant on the use of industrially-manufactured or so-called “synthetic” N fertilizers to maintain yields. However, excessive application of fertilizer N can lead to environmental problems such as eutrophication of surface waters, nitrate contamination of groundwater and increased emissions of the greenhouse gas, nitrous oxide. The use of organic fertilizers (crop residues, animal excreta, composts) as alternative or supplementary sources of N is a strategy that could limit potential environmental damage. In addition, the large increase in the production, marketing and consumption of organic foods in recent years has been a major force in the increased demand for organic fertilizers, since the use of synthetic fertilizers is prohibited in organic agriculture. Therefore, there is increased awareness of the important role that organic fertilizers can play in agriculture, and renewed interest in estimating the ability of organic fertilizers to supply N for crop uptake, either as a sole or complementary source of N. Quantifying the availability of N in organic fertilizer sources has been the subject of extensive investigation over many years. In its simplest form, it involves measurement of the difference in N uptake by a crop in the presence and absence of the organic fertilizer (i.e., the N difference method),
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which allows calculation of “apparent” N recovery (e.g., Kirchmann, 1990; Nannen et al., 2011; Paul and Beauchamp, 1995). The assumption is that the crop will take up the same amount of indigenous soil N irrespective of the treatment. However, there is considerable evidence that this assumption is invalid. A more complex but little used experimental approach consists of determining the “synthetic” fertilizer N equivalence of an organic fertilizer source, which involves a comparison of the yield or N uptake by a crop at a given rate of organic fertilizer addition with the response curve of several rates of “synthetic” N fertilizer (e.g., Cusick et al., 2006a; Mun˜oz et al., 2004). However, the non-isotopic methods suffer from greater variability (Cusick et al., 2006a; Mun˜oz et al., 2004). Organic fertilizers such as animal excreta and composts are naturally enriched in the stable isotope 15N, and this can be used as a qualitative tracer to follow the dynamics of N in conventional and organic farming systems (Chalk et al., 2014, 2019; Ina´cio et al., 2015; Ina´cio and Chalk, 2017). Alternatively, it is possible to artificially enrich organic fertilizers with 15 N and use this as a quantitative or semi-quantitative tracer to differentiate the labeled organic N source from the unlabeled indigenous soil N. For example, it is a simple matter to produce 15N-enriched plant material by applying 15N-enriched fertilizer, and numerous studies have been conducted on the recovery of 15N-labeled crop residues by subsequent crops. 15Nlabeled crop residues or grain can be fed to animals to produce 15N-labeled excreta, which can be taken one step further to produce 15N-enriched compost (Chalk et al., 2013). Twenty-one years ago, Dittert et al. (1998) published a review on 15Nbased studies of N turnover in soil following application of animal feces and slurry. The objective of the present review is to complement and extend the earlier review with an analysis of the more recent and extensive literature, while also providing a somewhat different emphasis and perspective. The review will cover 15N-labeling strategies of both fecal and urinary N, the uniformity of 15N-labeling within and between the components of excreta, transformations and crop recovery of excreta N added to soil, leaching and gaseous N losses, interactions of excreta N with synthetic fertilizer N, and the residual value of excreta N in soil.
2. Production of 15N-enriched animal excreta Animal excreta is composed of feces (solid or semi-solid) and urine (liquid). Feces and dung are interchangeable terms. On the other hand, manure can have a dual meaning, either the solid fraction or an admixture
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of dung and urine, the latter being commonly known as slurry. In order to circumvent possible confusion, we will refer to the constituents of excreta as feces, urine and slurry, and will avoid the use of the term “manure” except where “farmyard manure” or “green manure” are in common usage. Several methods have been used to introduce an enriched 15N label into animal excreta, which is composed of both organic and inorganic N constituents within feces and urine components. The methods are summarized in Table 1. The natural approach is to feed animals with 15N-enriched forage or grain and then collect and preserve the excreta produced. The artificial approach is to collect urine or slurry from animals, or synthesize artificial urine, and enrich it with 15N by addition of 15 NH4 + or 15N-enriched urea.
2.1 Feeding animals
15
N-enriched plant materials or urea to domestic
A range of 15N-labeled forages (grass, silage, hay) have been fed to sheep and goats (Table 2) and cattle (Table 3) while grains (barley, peas, soybean, rice, maize) have been fed to poultry (Table 4) and pigs (Table 5) to obtain 15 N-labeled excreta. In one case labeled ryegrass was fed to rabbits (Wu et al., 2010). 15N-labeled forage can be produced by addition of the isotope to the soil or hydroponic solution culture, or by foliar application of urea with a surfactant and urease inhibitor (e.g., Ingold et al., 2018). A non-lactating animal is often used so that isotope will not be excreted in milk (e.g., Garza et al., 2009; Hoekstra et al., 2011; Mun˜oz et al., 2004; Powell et al., 2004, 2005), although the feces composition may be slightly different compared to a lactating cow (Powell et al., 2004). A period of 1–3 weeks of pre-feeding the equivalent unlabeled forage was usually adopted before the changeover to the labeled diet (Tables 2–5), or fasting was employed prior to the feeding of labeled material (e.g., Primo et al., 2014). The period of labeled feeding was quite variable lasting from 36 h to several weeks (Tables 2–5), depending on the amount of material available and the test animal. Excreta collection generally continued for a period of several days following cessation of the labeled diet. In addition to feeding 15N-labeled plant material (the forage method), Powell et al. (2004) fed 15N-enriched urea to cows with unlabeled forage (the urea method) (Table 1). The authors claim that this method only produced labeled urine and fecal endogenous N, with undigested feed N remaining unlabeled. A variation of this technique was adopted by Powell et al. (2005), in which urea was administered periodically through a rumen fistula.
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Table 1 Natural and artificial strategies to enrich animal excreta with 15N. Labeling strategy Animal Reference
Feces and urine Fed 15N-enriched forage, silage or grain
Various
See Tables 2–5
Fed 15N-enriched urea with Cow unlabeled forage
Powell et al. (2004) and Hoekstra et al. (2011)
Add 15N-enriched urea to rumen through fistula
Cow
Powell et al. (2005)
Cow
Lee et al. (2014)
Add 15N-enriched urea or 15 NH4 + to unlabeled urine
Various
See Tables 10, 11, and 17
Add 15N-enriched urea + 15 N-glycine to unlabeled urine
Synthetic, Fraser et al. (1994), Di et al. (2002), and cow Silva et al. (2000, 2005)
Add 15 NO3 to unlabeled urine
Cow
Add pulses of rumen
15
NH4 + to
Urine
Monaghan and Barraclough (1993)
Slurry Add 15N-enriched urea or Various 15 NH4 + to unlabeled slurry
See Tables 12, 13, and 18
Mix 15N-enriched feces with 15N-enriched urine
Various
Chadwick et al. (2001), Mun˜oz et al. (2003, 2004), Cusick et al. (2006a,b), and Powell et al. (2004, 2005)
Mix 15N-enriched urine with unlabeled feces
Sheep
Bosshard et al. (2008, 2009)
Cattle
Hoekstra et al. (2011)
Mix 15N-enriched feces with unlabeled urine Add 15N-enriched urine to unlabeled slurry Add 15N-enriched feces to unlabeled slurry
Table 2
15
N enrichment of feed sources and excreta of sheep and goats. Time (d)
15
Reference
N-labeled Animal feed source
Adapta Feedb Collectb
He et al. (1992, 1994)
Goat
Rice straw
6–7
Catchpoole and Blair (1990)
Goat
Gliricidia, Leucaena 35
Sørensen et al. (1994a)
Sheep Ryegrass hay
Sørensen and Jensen (1996)
Sheep Ryegrass hay
Thomsen et al. (1997)
Sheep Ryegrass
31
38
Jensen et al. (1999)
Sheep Ryegrass hay
31
38
7
2–3
15
N (atom% excess)
Feed
14–17
Fecesc Urinec Peak
15
Nc (d)
5.92
2.5 (F, U)
3.70
10 (F)
1.5 (U) 3.0 (F) 9
17
4.52
35
35
4.73
2.91 2.85
5.19
4.04
3.25
3.96
2.65
2.03
31–37
2.93
2.77
38–44
3.06
2.94
2.88
2.58
19–22 (F)
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4.04
29–30 (U) Thomsen (2000)
Sheep Ryegrass
22
22
24–30
Thomsen (2001)
Sheep Ryegrass
22
22
Bosshard et al. (2008, 2009)
Sheep Ryegrass hay
7
9
9
Bosshard et al. (2011)
Sheep Ryegrass hay
7
9
11
14.23 10.96 8.54
Primo et al. (2014)
Goat
2d
2–3
2–3
4.81
Martı´nez-Alca´ntara et al. (2016b) Sheep Forage maize
7
18
Daily
Ingold et al. (2018)
7
a
Fed unlabeled material. Fed 15N-labeled material. F, feces; U, urine; S, slurry. d Fasting. b c
Goat
Brachiaria
Rhodes grass hay
3.96
3.30–5.61 (S)
1.99 2.28
0.31
16 (F, U)
0.16
12–19 (F)
Table 3
15
N enrichment of feed sources and excreta of cattle. Time (d)
15
N-labeled feed source
Reference
Powell and Wu (1999), Mun˜oz et al. (2003, 2004), Hay + silage and Cusick et al. (2006a,b) Barkle et al. (2001)
Fecesc Urinec Peak
7
1.97
1.5
8
3.66
1.27
3 21
Ryegrass hay
8
8
2.63
0.96
0.56
17
Daily
2.11
1.67
1.22
Garza et al. (2009)
Sudangrass
10
10
7
0.36
Hoekstra et al. (2011)
Pasture
7
3
5
2.63–9.63
Nannen et al. (2011)
Maize silage
Wachendorf and Joergensen (2011)
Ryegrass hay
17
Daily
2.48
2.00
1.58
Barros et al. (2017)
Alfalfa silage
4
4
0.26
0.25
0.16
Corn silage
0.21
0.20
0.12
Corn grain
0.19
0.14
0.10
Soybean meal
0.25
0.17
0.15
Fed unlabeled material. Fed 15N-labeled material. F, feces; U, urine; S, slurry. d Dung collected days 10–17 bulked; urine collected days 7–17 bulked. c
2.5 (F)
2.58
Hay + silage
b
Nc (d)
1.5 (U)
Lampe et al. (2006)
a
15
3 (F, U)
0.35 (S) 0.16
0.36 (S)
2–4 (F, U)
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Wachendorf et al. (2005, 2008)
Hay d
N (atom% excess)
Adapta Feedb Collectb Feed
Pasture
Langmeier et al. (2002)
15
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Phillip M. Chalk et al.
15
N enrichment of feed sources and feces of poultry. 15
Time (d)
15
Reference
Kirchmann (1990)
N-labeled feed source Adapta Feedb Collectb Feed
Barley grain
Abdelhamid et al. (2004)
Rice grain
Thomsen (2004)
Barley + peas
Liu et al. (2008) Cabbage Tagoe et al. (2008)
Rice grain
Holbeck et al. (2013)
Maize straw
Feces
Peak N (d)
15
1.543 1.034
Bergstr€ om and Barley grain Kirchmann (1999) Uenosono et al. Rice grain (2002)
N (atom% excess)
14
21
29
1.54
1.16
2.57
1.69
22
0.47 5
5.39c 4.25c
15 15
12.24
7
4.22 0.81–0.85
7
14
8.17
1.97
a
Fed unlabeled material. Fed 15N-labeled material. 35 g peas (4% N, 7.41 atom% 15N excess) + 85 g barley (1.82% N, 3.57 atom% 15N excess); , estimated from figure. b c
Powell et al. (2004, 2005) suggested that the forage method with a potentially high 15N enrichment was more suited to long-term studies, whereas the urea method with generally lower 15N enrichment was suitable for short-term studies. Several authors have commented on the difficulty of sampling feces and urine individually without cross contamination, and have therefore bulked the excreta to make slurry (e.g., Bosshard et al., 2008, 2009; Chantigny et al., 2004a,b; Jayasundara et al., 2010; Lampe et al., 2006; Nannen et al., 2011). In order to avoid the mixing of feces and urine, indwelling bladder catheters were fitted to pigs (Sørensen and Thomsen, 2005) and cows (Powell et al., 2004, 2017; Powell and Wu, 1999). Excreta were commonly preserved by freezing or the addition of acid to prevent NH3 volatilization.
Table 5
15
N enrichment of feed sources and excreta of pigs.
Reference
15
He et al. (1994)
Green manure
6–7
2–3
Chantigny et al. (2004a,b)
Soy + barley
7
Sørensen and Thomsen (2005)
Barley + peas
5
Jayasundara et al. (2010)
Corn + soybean
Cavalli et al. (2018)
Corn
a
Fed unlabeled material. Fed 15N-labeled material. F, feces; U, urine; S, slurry.
b c
N-labeled feed source
Adapt
7
a
Fecesc
Urinec
14–17
9.73
5.46
5.24
12
20
2.44
11
11
2.37
2.19
4
6
0.61–1.36
0.58–1.00 (S)
3–
6.08
Collect
b
N (atom% excess)
Feed
Feed
b
1.96 (S) 1.71
2.74 (S)
Peak
15
Nc (d)
8 (S) 11 (F, U)
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15
Time (d)
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2.1.1 Temporal change in excreta 15N abundance After the start of feeding of pigs with a mixture of 15N-enriched peas and barley grains, the 15N abundance of urine N quickly increased while that of feces was initially slower (Sørensen and Thomsen, 2005; Fig. 1A). However, after 3 d the 15N abundance of fecal N exceeded that of urinary N. A similar pattern was observed for sheep by Bosshard et al. (2011) (Fig. 1B) and Sørensen and Jensen (1998) (Fig. 1C) that were fed ryegrass hay, while the same phenomenon was observed for cows fed alfalfa silage (Barros et al., 2017; Fig. 1D). At the end of the 11-d feeding period, the 15N abundance of fecal N was 7% lower than in the feed (Sørensen and Thomsen, 2005; Fig. 1A), which
Fig. 1 Time course of 15N abundance of feces and urine of (A) pigs fed with a mixture of 15 N-enriched peas and barley grains, (B) and (C) sheep fed with 15N-enriched ryegrass hay, and (d) lactating cows fed with 15N-enriched alfalfa silage. Arrow in (D) denotes cessation of labeled feeding. Reproduced with permission from Panel (A): Sørensen, P., Thomsen, I.K., 2005. Production of nitrogen-15-labeled pig manure for nitrogen cycling studies. Soil Sci. Soc. Am. J. 69, 1639–1643; Panel (B): Bosshard, C., Oberson, A., Leinweber, P., Jandl, G., Knicker, H., Wettstein, H.-R., Kreuzer, M., Frossard, E., 2011. Characterization of fecal nitrogen forms produced by a sheep fed with 15N labeled ryegrass. Nutr. Cycl. Agroecosyst. 90, 355–368; Panel (C): Sørensen, P., Jensen, E.S., 1998. The use of 15N labelling to study the turnover and utilization of ruminant manure N. Biol. Fertil. Soils 28, 56–63; and Panel (D): Barros, T., Powell, J.M., Danes, M.A.C., Aguerre, M.J., Wattiaux, M.A., 2017. Relative partitioning of N from alfalfa silage, corn silage, corn grain and soybean meal into milk, urine, and feces, using stable 15N isotope. Anim. Feed Sci. Technol. 229, 91–96.
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was attributed to excreted unlabeled endogenous N (Sørensen et al., 1994a), while the 15N abundance of urinary N was 28% lower than in the feed. Milk had a slightly lower 15N abundance than urine but followed the same trend (Barros et al., 2017; Fig. 1D), clearly illustrating the economy of using a non-lactating cow for production of labeled excreta. In order to obtain uniformly labeled feces or urine, the daily collections of each excreta type were combined once a stable plateau in 15N abundance was reached (Fig. 1). For example, Wachendorf et al. (2008) bulked urine collected between days 10 and 17 while feces collected between days 7 and 17 were combined when a cow was fed with 15N-enriched grass silage. 2.1.2 Recovery of labeled dietary N in the excreta The fraction of labeled dietary N recovered in the excreta is given by Eq. (1): Labeled dietary N recovery ¼ Ndiet 15 N enrichmentdiet = Nexcreta 15 N enrichmentexcreta
(1)
where 15N enrichment is expressed as atom% 15N excess. 15N enrichment is determined by subtracting the 15N abundance (atom% 15N) of the equivalent unlabeled diet and excreta from the labeled diet and excreta, respectively. The fractional recovery can be expressed as a percentage by multiplying by 100. Few quantitative data exist on the recovery of labeled dietary N in excreta (Table 6). When 15N-labeled rice straw was fed to goats for 2–3 days, 28 and 6% of dietary 15N excess was recovered in feces and urine, respectively (He et al., 1992). A considerably higher percentage of excess 15N in green manure fed for 2–3 days to pigs was recovered in urine (29%), while an approximately equal amount (24%) was recovered in feces (He et al., 1994). Similar amounts of feed-derived excess 15N were also recovered in feces (29%) and urine (31%) of cows fed labeled alfalfa hay and corn silage for 36 h (Powell and Wu, 1999). On the other hand, Uenosono et al. (2002) estimated that 41% of 15N-labeled rice grain fed for 21 days to poultry was voided in feces. In a study involving lactating dairy cows, Barros et al. (2017) found consistent recoveries of four 15N-labeled forages (alfalfa silage, corn silage, corn grain, soybean meal) within feces (26–27%) and within urine (37–39%). Recovery in milk was similar to feces (22–25%). The loss of 50–65% of dietary N in excreta indicates a low efficiency of conversion to meat and milk.
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Table 6 Recovery of 15N-labeled plant materials fed to domestic animals. 15 15 15
N (atom% excess)
N recovery (%)
Reference
N-labeled Animal feed source Feed Feces Urine Feces Urine
He et al. (1992, 1994)
Goat
Rice straw
He et al. (1994)
Pig
Green manurea
9.73 5.46
Hay + silagec
3.66 1.97
Powell and Wu (1999)b Cow
Uenosono et al. (2002) Poultry Rice grain Barros et al. (2017)
Cow
d
5.92
28
6
5.24
24
29
1.27
29
31
2.57 1.69
Alfalfa silage 0.26
Fig. 1D
41 26
39
Corn silage 0.21
27
38
Corn grain
0.19
27
37
Soybean meal
0.25
26
38
a
Milk vetch + cowpea + rape. The same feeding procedure was used by Mun˜oz et al. (2003, 2004) and Cusick et al. (2006a,b). Alfalfa hay + corn silage. d Lactating. b c
On the other hand, this low efficiency is a boon for studies of 15N-enriched excreta, giving a more uniform labeling than can be achieved by adding labeled urea or ammonium to urine or slurry (Section 3).
2.2 Addition of 15N-enriched urea or ammonium to unlabeled animal urine More than 60% of N excreted from cattle and sheep is in urine (Haynes and Williams, 1993). The concentrations of N containing constituents of urine from dairy cattle were reviewed by Dijkstra et al. (2013). Many studies have been conducted with animal urine which has been artificially-labeled with 15 N (Table 1). Since 60–80% of the N in urine occurs as urea (Dijkstra et al., 2013; Kirchmann, 1991; Sørensen and Jensen, 1996) it is logical to label urine by addition of a small quantity of urea highly labeled in 15N (99 atom%), which has been adopted in the majority of studies (Table 1). However, in a minority of studies 15 NH4 + has been added rather than urea, since urea will be rapidly hydrolyzed to NH4 + on contact with soil, while in other studies 15N-labeled glycine has been added together with the 15N-urea
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Table 7 Synthetic urine formulations.
Reference
Urea
Constituent (g L21) Hippuric K2SO4 KBr Glycine acid Total N
KHCO3 KCl
de Klein and van 28.50 22.90 16.9 – Logtestijn (1994), Ambus et al. (2007), and Carter (2007)a
–
Fraser et al. (1994), 23.75 22.15 Clough et al. (2003), and Clough and Kelliher (2005)
3.95 6.70
6.35 6.15
Clough et al. (1996, 1998)
4.20 2.30
6.70 4.84
23.30
Shand et al. (2000) and Williams et al. (2003)
42.8 46.2
–
7.6 3.8
21.4
Clough et al. (2004) 17.40 23.33
8.35 2.29
4.84
Welten et al. (2013) 13.6 13.9
5.0 1.5
3.4
Ayadi et al. (2015) a
22.6 23.1
11.9
15.6
10.0
9.0
b
3.8 1.9
1
Minor constituents (g L ) not shown; uric acid, 0.2; NH4Cl, 1.4; allantoin, 0.6; creatinine, 0.3. Authors state it was potassium chlorate (KClO3).
b
in the ratio of 1:9, in order to label part of the organic N fraction of urine (e.g., Carey et al., 2017, 2018; Di et al., 2002; Fraser et al., 1994). In addition to the use of animal urine, several authors have used synthetic urine (Table 7) presumably to avoid the inconvenience and complication of collecting animal urine uncontaminated by feces.
2.3 Addition of 15N-enriched ammonium, urea, urine or feces to unlabeled animal waste slurries Slurry is normally defined as a mixture of fecal and urinary N in suspension. However, a slurry can also consist of a mixture of feces and water without urine (e.g., Martı´nez-Alca´ntara et al., 2016b; Sørensen and Jensen, 1995a, 1998). Many studies have been conducted with slurries of feces + urine which have most often been artificially-labeled with 15N by addition of 15 N-enriched ammonium salts or urea (Table 1). Feces contains 2–3% organic N, no nitrate and little ammonium (Thomsen et al., 2003), while
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total N in fresh poultry excreta consists of 61% uric acid N (Kirchmann, 1991). Hydrolysis of urea or uric acid to ammonium is rapid, and after several hours or days, 50–60% of slurry N is present as ammonium-N, which forms the rationale for addition of 15N-enriched ammonium to artificially label the slurry. Several variations for obtaining 15N-labeled slurry have been employed (Table 1). For example, Hoekstra et al. (2011) labeled slurry by adding labeled urine or feces to unlabeled slurry. The treatments were (i) 15Nlabeled urine obtained by feeding labeled herbage was added to unlabeled slurry; (ii) 15N-labeled feces obtained by feeding 15N urea with unlabeled herbage was added to unlabeled slurry; (iii) 15N-labeled feces obtained by feeding labeled herbage was added to unlabeled slurry.
3. Uniformity of 15N-labeling of excreta Feces are mainly composed of organic N compounds synthesized during passage of plant material through the animal gut as well as residual (undigested) organic N. Urine is a mixture of various organic N compounds and inorganic N derived from the hydrolysis of its principal constituent, urea. The importance of uniform 15N-labeling of the components of excreta has been expressed by several authors (e.g., Chantigny et al., 2004b; Sørensen and Jensen, 1998). A heterogeneous distribution of 15N between the rapidly and the slowly mineralizable N pools of animal excreta will distort estimates of the actual rates of N mineralization and hence crop recovery (Sørensen et al., 1994a), which are then a function of both elapsed time and the relative contribution of the various N pools to mineral 15N (Chantigny et al., 2004b). Therefore it is important to ascertain the extent to which there is isotopic uniformity within the components of animal excreta (feces and urine) if used individually as well as within these components if they are combined in slurry. It is also important to determine if feeding and sampling strategies can be devised to minimize non-uniformity, and also to estimate the likely errors in plant recovery of 15N-labeled excreta due to a non-uniform distribution of 15N.
3.1 Within feces The uniformity of 15N-labeling of feces has been tested by total and extractable N analyses (Bosshard et al., 2011; Langmeier et al., 2002; Sørensen et al., 1994a) or through sequential acid hydrolysis techniques (Kirchmann, 1990; Uenosono et al., 2002) (Table 8). Inconsistent differences were found
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Table 8 Distribution of 15N in bulk material or N fractions of labeled feces. 15 N (atom% g N kg21 Recovery excess)a DM (%) Reference Animal N fraction
Kirchmann (1990)
Poultry Total N
Sørensen Sheep et al. (1994a)
Bosshard Sheep et al. (2011)
1.034
0.27 M H2SO4
1.021
1.75 M H2SO4
1.014
12.5 M H2SO4
1.049
Total N
30.8
NH4 +
0.36
1.2
2.96
H2O soluble
7.0
25.0
3.83
91.2 0.3
1.65 0.03 bc
7.7 0.1
1.67 0.01 bc
Amide
5.5 0.3
2.67 0.49 a
Hexosamine
21.9 1.8
1.44 0.03 bc
α-Amino
28.4 1.0
1.82 0.06 b
Unidentified
28.5 3.1
1.44 0.10 bc
Non-hydrolysable
7.3 0.5
1.23 0.06 c
Total N
100.0
0.962 0.001 b
Undigested
10.7 0.44 0.648 0.028 a
Debris
76.9 1.24 0.997 0.011 b
H2O soluble
12.5 1.43 1.014 0.040 b
Total N
100.0
10.93 0.03 ab
Undigested
33.0
10.33 0.05 b
Debris
53.1
11.63 0.16 a
H2O soluble
13.6
9.48 0.50 c
Uenosono Poultry Hydrolysable et al. (2002) NH4 +
Langmeier Cow et al. (2002)
14.6
3.70
a Different lowercase letters within individual studies denote significant differences (P < 0.05) in enrichment between N fractions.
15
N
among total and identifiable extractable N fractions of sheep (Bosshard et al., 2011; Sørensen et al., 1994a) and cow (Langmeier et al., 2002) feces (Table 8). However, a reasonably uniform 15N distribution in poultry excreta was indicated by similar 15N signatures in the bulk material and N fractions sequentially extracted with H2SO4 (Kirchmann, 1990). Uenosono et al. (2002)
ARTICLE IN PRESS 16
Phillip M. Chalk et al.
similarly found non-significant differences in the 15N signatures of the bulk material, total hydrolysable N, NH4 + , hexosamine N, α-amino N and unidentified N (1.44–1.82 atom% excess) in poultry excreta. However, amide N was significantly higher and non-hydrolysable N was significantly lower in 15N enrichment compared with the other fractions, but they represented only small percentages of the total (5.5% and 7.3%, respectively). The uniformity of the 15N enrichment of sheep feces has also been appraised by an incubation technique proposed by Sørensen et al. (1994a). Moist and homogenized labeled feces (10 mg N) was mixed with dry quartz sand (50 g), adjusted to 55% of the water holding capacity and incubated in bottles covered with Al foil at 20 °C. Water loss was replenished weekly and samples were extracted at various times with 2 M KCl for determination and isotope-ratio analysis of inorganic N (NH4 + + NO3 ). Using the 15N enrichment of the mineralizable N of sheep feces (as determined by Sørensen et al., 1994a) rather than that of the sheep total fecal N, Sørensen et al. (1994b) demonstrated that the 15N recovery by a barley crop in three soils increased by only 3% (from 14% to 17%). Based on the sand incubation technique, Sørensen and Jensen (1998) concluded that it is possible to produce nearly uniformly labeled ruminant feces. On the same basis, Sørensen and Thomsen (2005) found that labeled pig feces had a relatively homogeneous 15N enrichment, even though the diet of labeled pea and barley grain differed in 15N enrichment.
3.2 Within urine The labeling of urine N derived from the feeding of a 15N-enriched diet can be regarded as homogeneous ( Jensen et al., 1999; Sørensen and Jensen, 1996). For example, Sørensen and Jensen (1996) found that the ammoniacal-N and total N in urine had similar 15N abundances (3.22 and 3.28 atom% 15N, respectively) after feeding labeled ryegrass to sheep for 1 month. Alternatively, several authors have prepared 15N-labeled artificial urine by adding both labeled urea and labeled glycine in the ratio of 9:1 (Di et al., 2002; Fraser et al., 1994; McLaren et al., 1993; Silva et al., 2000, 2005). While uniform labeling can be achieved between these two components of urine, the other organic nitrogenous constituents of artificial urine (Table 7) do not isotopically exchange with urea and glycine and are therefore not uniformly labeled. Therefore, the feeding of 15N-enriched plant materials to animals appears to be the optimum strategy to achieve uniformly labeled urine, although as noted previously, it is difficult to obtain urine uncontaminated by feces.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
17
3.3 Between feces and urine When fed an 15N-enriched diet, feces N was consistently more enriched than urine N, irrespective of the animal species (Tables 2, 3, and 5; Fig. 1). Chalk et al. (2014) also observed the same relative difference in their review of 15N natural abundance of animal feces and urine. According to Sørensen and Thomsen (2005), the difference in 15N enrichment of feces and urine makes it difficult to label total slurry N uniformly. As a consequence, these authors recommend that the dynamics of urine and feces N should be followed separately as the lability of N in these components is different ( Jensen et al., 1999). For example, Chantigny et al. (2004b) found that the 15N enrichment of the N mineralized from an admixture of feces and urine was less than the 15N enrichment of the total N pool. Therefore Sørensen and Thomsen (2005) recommend that the labeled component be mixed with the other excreta components in unlabeled form as practiced by several authors (e.g., Jensen et al., 1999; Thomsen et al., 1997). This allows the fate of each component to be estimated separately, while the fate of the total excreta N can be calculated from the weighted recovery of N from each component. As an alternative, Sørensen and Thomsen (2005) suggested that feces and urine having similar 15N enrichments can be mixed.
3.4 Within slurry As noted previously, slurry is not uniformly labeled with 15N whether produced naturally by feeding 15N-enriched forage or grains, or whether it is artificially produced through addition of 15N-enriched urea or ammonium salts. In the latter case, the added isotope will only equilibrate with the mineral N fraction of the slurry, and will not mix initially with the large organic N component of the slurry. In recognition of the non-uniform distribution of 15N within slurry, several authors have expressed the 15N abundance of slurry on the basis of the NH4 + fraction, rather than the total N content (e.g., Dittert et al., 2001; Dosch and Gutser, 1996; Paul and Beauchamp, 1995; Sørensen and Jensen, 1995b; Trehan, 1994). For example, the 15N abundance of the total slurry N and the ammonium-N in the slurry were 0.98 and 1.25 atom% 15N, respectively (Chadwick et al., 1998) and 1.45 and 4.29 atom% 15N, respectively (Dittert et al., 2001). Therefore, the recovery of labeled slurry N by plants is a measure of the availability of the NH4 + fraction of the slurry and not the total slurry N per se, thus compromising comparisons of recovery with uniformly labeled feces, urine or synthetic fertilizer. The recoveries of slurries enriched in 15N by addition of labeled inorganic N or urea, can therefore only be regarded as semi-quantitative.
ARTICLE IN PRESS 18
Phillip M. Chalk et al.
4. Recovery of
15
N-labeled excreta in plants and soil
The proportion of N in the plant derived from the labeled excreta (Ndfeplant) is given by Eq. (2), based on the assumption that the excreta is uniformly labeled. Ndfeplant ¼ 15 N enrichmentplant =15 N enrichmentexcreta
(2)
where 15N enrichmentplant ¼ 15N abundanceplant – 15N natural abundanceplant. 15 N natural abundanceplant is determined by analysis of the plant growing in the same soil under the same conditions without added excreta. The unit of 15N abundance is atom% 15N, while the unit of 15N enrichment is atom% 15 N excess. Eq. (2) is used to calculate the proportion of N in the soil derived from the labeled excreta by replacing “plant” with “soil.” The recovery of labeled excreta N in the plant (Rplant) is given by Eq. (3) Rplant ¼ Ndfeplant Nplant =ðNdfeexcreta Nexcreta Þ (3) where N is the total N content [N concentration (mg g1) dry matter (g)]. Eq. (2) is used to calculate the recovery of labeled excreta N in the soil by replacing “plant” with “soil.” Recoveries are expected to be season- and species-specific (annual vs perennial). Other variables affecting recoveries in plants and soil include the form of excreta (feces, urine, slurry), method of application (e.g., surface, banding, injection, etc.), soil and excreta pH, soil total N and excreta N rate, method of 15N-labeling and experimental scale (laboratory, pot, lysimeter and field) and duration.
4.1 Feces Relatively few studies have been conducted on the recoveries of labeled feces in plants and soil (Table 9) compared with those with urines (Section 4.2) and slurries (Section 4.3). Laboratory, pot, lysimeter and field studies were conducted using surface soils of acidic and alkaline pH, and with variable total N contents (Table 9). Feces derived from several domestic animals were obtained by feeding an 15N-enriched diet of forages or grains. Rates of feces additions were quite variable, ranging from 92 to 8000 mg kg1 soil in laboratory and pot studies, and from 87 to 1052 kg ha1 in lysimeter and field studies. Feces was mixed with the soil (Nishida et al., 2004; Primo et al., 2014; Sørensen et al., 1994b; Wu et al., 2010), banded (Thomsen et al., 2003) or
Table 9 Recovery of 15N-labeled feces in crops and soil in laboratory, pot, lysimeter and field experiments. Soil Feces added Reference
15
N recovery (%)
15
Rate Total pH N (g kg21) Animal (kg ha21)a
N (atom%) Crop and duration
6.4 1.3
Sheep (92)
4.18
7.0 1.5
(94)
7.4 1.5
(104)
Crop Soil
Total
Laboratory studies
Cusick et al. (2006b)
7.6 0.3
Cow
14.7
5.0 0.9
Rabbit (150)
Not applicable. Soil was incubated for 28 d
NA, 168 d
89–102
26
26
Pot studies Wu et al. (2010)
19.4
7.3 1.3 Primo et al. (2014)
Martı´nez-Alca´ntara et al. (2016a)
6.7 0.5
8.4
Goat
(8000)
Sheep 20 g tree
2.35
1
2.54
Rice-wheat rotation, harvested at maturity
8, 8
Maize, 50 d
7
Cotton, 50 d
7
Cowpea, 50 d
8
Mandarin, 10 months
30
69, 40 77, 48
16, 5 68, 39 84, 44
32b
62 Continued
ARTICLE IN PRESS
Thomsen et al. (2003)
Table 9 Recovery of 15N-labeled feces in crops and soil in laboratory, pot, lysimeter and field experiments.—Cont’d Soil Feces added
15
N recovery (%)
15
N (atom%) Crop and duration
Crop Soil
Total
Sørensen et al. (1994b)
8.0 1.8
Sheep 87
3.93
Barley + ryegrass, 18 months
24
100
Wachendorf et al. (2005)
5.9 2.7
Cow
1052
2.04
Pasture, 2 y
Pig
459
Cow
1052
Lysimeter studies 76
75c
Field studies Nishida et al. (2004) Wachendorf and Joergensen (2011) 5.1 Data in parentheses are mg kg1. Includes 2% as NH4 + + NO3 . c 2-year average. d In microbial biomass, 2-year average. a
b
2.2
Rice, 113 d 2.00
Pasture, 189 d
25
57 16d
82
ARTICLE IN PRESS
Rate Total pH N (g kg21) Animal (kg ha21)a
Reference
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
21
applied to the soil surface (Martı´nez-Alca´ntara et al., 2016b; Wachendorf et al., 2005; Wachendorf and Joergensen, 2011). Cereal, pasture and fruit crops were grown and harvested over periods ranging from 50 days to 2 years. Given the contrasting experimental conditions, it is not surprising that plant recoveries were quite variable, ranging from as little as 7% to as much as 30%, while soil recoveries were generally higher, ranging from 16% to 76% (Table 9). On two occasions, quantitative recoveries of labeled feces in plants and soil were obtained, while total recoveries often exceeded 75% for cereals as a first rotation crop (Table 9).
4.2 Urine Laboratory, pot and lysimeter studies conducted with 15N-labeled urine are summarized in Table 10. All but one of the soils were acidic while total N ranged from a low of 0.7 to a high of 18.5 g kg1 soil. However, other than this single maximum value all were <8.8 g kg1 soil. Synthetic or natural urine from a range of animals was applied to the soil surface at rates ranging from 26 to 100 g N m2. Grasses grown alone or in mixed swards with legumes were cut at various intervals, from a single cut at day 28 to multiple cuts finishing at year 2 (Table 10). Recoveries of urine N in plant material were very variable, ranging from as little as <1% to as much as 58%, while soil recoveries were generally <30% (excluding laboratory studies). In a few cases measurable quantities of NH4 + + NO3 were present. The highest total recovery was 86%, but several values were below 50%. Field studies conducted with 15N-labeled urine are summarized in Table 11. All but one of the soils were acidic with total N ranging from 0.8 to 3.8 g kg1 soil. Natural urine derived from either sheep or cattle was applied at rates ranging from 6 to 105 g N m2. With only one exception (370-day wheat), either pasture or pasture grasses were grown and cut at various intervals, starting with a single cut at day 14 and finishing with multiple cuts at day 350. Plant and soil recoveries ranged from 1% to 65%, and from 13% to 66%, respectively. Total recoveries were within the range of 37–88%. The lack of quantitative recoveries in plants and soil indicates the potential for losses of urine N via leaching and gaseous N emissions (Section 7). In addition, the recovery data will depend on how the urine was labeled, and on how the 15N enrichment of the urine was expressed, i.e., as total urine N or as the inorganic N fraction of the urine with which added 15N equilibrated.
Table 10 Recovery of 15N-labeled animal urine in crops and soil in laboratory, pot and lysimeter experiments. 15 Soil Urine N addeda N recovery (%) Reference
pH
Cropa and N (atom%) duration
Total N (g kg21) Typeb g m22
15
0.7
2.0
Soil
NH4+ + NO32 Total
NA, 28 d
30
32
NA, 42 d
75
12
Crop
Laboratory studies Bronson et al. (1999) 5.0
Synt
50
7.7 Cusick et al. (2006b) 7.6
62
5.3 0.3
Cow 14.7
NA, 168 d
63
63
Pot studies Williams et al. (2003) Ambus et al. (2007)
5.6
Uchida et al. (2011) 5.6
6.6
Synt
50
2.0
G, 56 d
0.8c
28
15
Synt
26–51 5.2
P, 42 d
18–20
10–20
8–20
48
Cow 59
0.996
R, 28 d
1.6–7.0
McLaren et al. (1993)
Synt
50
5.0
P, 1 y
40, 44d
26, 20d
66, 64d
Clough et al. (1996) 4.9–5.5 (three soils)e
Synt
50
2.0
P, 150 d
11–35
13–21
32–48
100
4.81
P, 288 d
22–31
21–24
68–81
Lysimeter studies
Clough et al. (1998) 5.3–6.2 4.5–18.5 Synt (four soils)
ARTICLE IN PRESS
Clough et al. (2003) 4.7
Sheep 20.5
Di et al. (2002)
5.3
2.0
Decau et al. (2003)
Cow 100
5.0
P, 365 d
58, 50f
28, 25f
86, 75f
Cow 52
2.84
P, 2 y
37–49g
23–31g
67–77g
5.0
P, 1 y
58
28
86
5.3
2.0
Menneer et al. (2008) 6.0
4.2
Cow 77.5
4.65
P, 196 d
20–27
24–27
44–53
Shepherd et al. (2010)
5.9
5.6
Cow 50
5.16
P, 247 d
48
19
67
Welten et al. (2013) 5.9
8.8
Synt
4.65
P, 300 d
26
24
50
Cow 70
5.0
P, 17 months 40, 50, 18h 17, 16, 14h
47, 66, 32h
Cow 35
9.0
IR, 76 d
5
31
37
O, 96 d
5
27
32
IR, 76 d
5
20
24
O, 96 d
5
23
27
Woods et al. (2017) 5.7, 6.3 Carey et al. (2017)
6.1
4.0
100
60
70
a
NA, not applicable; G, grass (Agrostis capillaris); R, ryegrass (perennial) (Lolium perenne); P, pasture; IR, Italian ryegrass (Lolium multiflorum); O, Oats (Avena sativa). Synt, synthetic. Regular cutting twice weekly. d Data are for subsoiled and non-subsoiled treatments, respectively. e Data are for soils without a water table. f Values are for urine and urine + dairy effluent, respectively. g Range of data are for three soils (pH 8.0, 5.8, 6.7; total N, 2.4, 2.0 and 1.2 g N kg1, respectively) over 2 years. h Three pasture types (perennial ryegrass-white clover; Italian ryegrass; lucerne). b c
ARTICLE IN PRESS
Silva et al. (2005)
Table 11 Recovery of
15
N-labeled animal urine in crops and soil in field experiments. Soil Urine N added pH
Total N (g kg21)
Type
Vallis and Gardner (1984)
8.4
0.8
Cattle 12.8–26.6
g m22
Vallis et al. (1985)
6.2
0.8
Cattle 15.0
Whitehead and Bristow (1990)
6.2
3.4
Cow 74.4
5.1
0.6
5.8, 6.0 3.8, 2.7
Leterme et al. (2003) (three times, two rates) Bol et al. (2004)
1.1 5.5
Crop and duration Crop
Soil
Total
Pasture, 28 d
42–66
50–68
58
65
2–8 5–7
4.37
Grass, 321 d
23
14
37
Cattle
4.8
Pasture, 150 d
19
40
60
Sheep 12.3
4.87
Pasture, 70 da
42
33
5.23
c
Pasture, 38 d
47
29
14
23
37
4.36
Wheat, 370 d
46.1
3.78
Wheat, 240 df
17
22g
39
Sheep 7.7
3.4
Pasture, 350 d
50, 35
20, 25
70, 60
Cow 6.1, 7.5
0.87–1.02 Ryegrass, 168–350 d
49–65, 30–61
23–31, 27 77–88, 57–88
Cow 23–40
17.4
1–4
47
Pasture, 14 d
1.58
Pasture, 27 weeks
Taghizadeh-Toosi et al. (2011)
Cow 93
4.96
Pasture, 58 d
Urine applied October 19, 1992 (Experiment 3). Dry season. Urine applied September 11, 1992 (Experiment 3). d Includes 8% NH4 + + NO3 . e Urine applied November 29, 1990; wheat sown June 26, 1991 and harvested December 4, 1991 (Experiment 1). f Urine applied April 8, 1991; wheat sown June 26, 1991 and harvested December 4, 1991 (Experiment 1). g Includes 5% NH4 + + NO3 . h In microbial biomass, 2-year average. b c
76
9.8
Cow 105
a
75 d
e
Wachendorf and Joergensen (2011) 5.1 5.5
b
Pasture, 63 d
25.9
Williams and Haynes (2000)
N (atom%)
13 3
48–51 h
ARTICLE IN PRESS
Thompson and Fillery (1998)
Templeton sil
N recovery (%)
15
Reference
Williams and Haynes (1994)
15
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
25
4.3 Slurry Laboratory studies conducted with 15N-labeled slurry are summarized in Table 12. Slurry was labeled either by feeding a pig with 15N-enriched maize (Cavalli et al., 2018; Table 5), or by addition of 15 NH4 +. The soils used were all acidic and varied in total N from 0.9 to 3.2 g kg1 soil. Slurry was mixed with the soil (Aita et al., 2012; Clark et al., 2009; Paul and Beauchamp, 1995; Trehan, 1994) or surface-applied (Aita et al., 2012; Moal et al., 1994). All slurries were alkaline in pH and were applied at rates from 0.08 to 2.78 g kg1 soil (Table 12). The incubation periods lasted from 2 to 133 days (Table 12). Quantitative recovery of NH4 + -labeled slurry was obtained in two studies (Cavalli et al., 2018; Clark et al., 2009), while there was no difference in soil recovery between surface and incorporated slurry (Aita et al., 2012). Pot studies conducted with 15N-labeled slurry are also summarized in Table 12. Soils were acidic or alkaline and varied in total N from 0.9 to 2.1 g kg1 soil. Slurry was labeled by addition of 15N-enriched urea (Chadwick et al., 2001) or by addition of 15 NH4 +. Slurry was neutral, strongly alkaline or slightly acidic, and was applied at rates from 0.12 to 5.55 g kg1 soil. Slurry was either surface-applied (Chadwick et al., 2001), mixed with the soil (Dosch and Gutser, 1996; Sørensen and Jensen, 1995b; Trehan and Wild, 1993), mixed with 3/5 of the soil (Paul and Beauchamp, 1995) or applied as a “simulated injection” (Chadwick et al., 2001; Sørensen and Jensen, 1995b). Perennial and annual crops were grown for varying periods up to 64 days (Table 12). Total recoveries ranged from 33% to 97%. Recovery in herbage was consistently higher in three soils for “injected” vs mixed application (Sørensen and Jensen, 1995b), while Chadwick et al. (2001) found higher total recovery of 15N-urea in “injected” (76%) vs surface application (53%). Lysimeter studies conducted with 15N-labeled slurries are summarized in Table 13. All slurries employed in lysimeters were artificially-labeled with 15 NH+4 and were surface-applied with or without some mixing with the surface soil. The soils were either acidic or alkaline while slurries were alkaline. Total recoveries in rotation crops or pastures and soil over periods between 1 and 5 years were all <50%, indicating that labeled inorganic N rather than total slurry N per se was subject to considerable loss. Field studies conducted with 15N-labeled slurries are also summarized in Table 13. Soil pH was neutral or acidic with total N varying from 0.4 to 2.6 g kg1 soil. Slurry pH was naturally neutral to alkaline, but was also artificially adjusted with acid to give a range of pH values of 5–7 (Park et al., 2018). Various methods were used to apply slurry including surface spreading,
Table 12 Recovery of 15N-labeled animal waste slurries in crops and soil in laboratory and pot experiments. Soil Slurry N addeda g kg soil
21
pH
Total N (g kg21)
Type
Trehan (1994)
6.0
0.9
Dairy
Moal et al. (1994)
5.3
1.7
Pig
2.1
Dairy 7.5 0.35
Reference
pH
15
N (atom%)
15
N recovery (%)
b
Crop and duration
Cropb Soil
NH4+ + NO32 Total
Laboratory studies
Paul and Beauchamp (1995)
0.48 7.8
14.16
NA, 9 d
34
2.51
NA, 2 d
55
NA, 21 d
6.3, 6.0 3.2, 1.5
Pig
8.3 2.78
7.29
NA, 133 d
Aita et al. (2012)
5.2
0.9
Pig
8.2 0.08
2.76
NA, 95 d
Cavalli et al. (2018)
7.9
1.7
Pig
7.4e 0.07
2.46e
NA, 112 d
8.2f
2.01f
79 55
54
54 98 8, 105 6
5d
5d 98 1 100 1
Pot studies Trehan and Wild (1993)
6.1
Dairy
0.41
8.16
Potato, 98 d
2.1
Dairy 7.0 0.35
5.10
Maize, 5–7th leaf 57g
57
Sørensen and Jensen (1995b) 6.2–7.9 1.1–1.6 (three soils)
Cattle 6.8 0.92
1.43
Ryegrass, 180 d
60–64 23–39
77–97
Dosch and Gutser (1996)
1.2
Cattle
0.12
14.4
Oats, flowering
52
6
58
1.7
Pig
8.5 5.55
8.31
Grass, 8 d
2–7
6–8
Paul and Beauchamp (1995)
6.4
Chadwick et al. (2001)
Contained from 30% to 88% NH4 N. NA, not applicable. c Includes clay-fixed NH4 + . d In the absence of wheat straw for both surface-applied and incorporated slurry. e Raw slurry. f Digested slurry. g Two crops of maize. a
b
+
21
47
9c
0.9
25–55
77
33–70
ARTICLE IN PRESS
Clark et al. (2009)
45c
Table 13 Recovery of 15N-labeled animal waste slurries in crops and soil in lysimeter and field experiments. Soil Slurry N added Reference
pH
Total N (g kg21) Type
pH
g m22
15
N recovery (%)
15 N (atom%)
Crop and duration
Crop
Soil
Total
9.37
Pasture, 1 y
35
14
49
12–15
Rotation, 5 y
24–30
Lysimeter studies Cameron et al. (1995)
7.6
Pig Cattle
13.4
24–30
Carey et al. (1997)
7.5
3.6
Pig
7.5 20, 40
9.07
Pasture, 730 d
20, 20 17, 14 37, 34
Di et al. (1999)
5.3
2.0
Dairy
8.4 20
10.0
Pasture, 365 d
24a
24
2.1
Dairy
7.0 0.35
4.62
Maize, 125 d
15
15
Field studies Paul and Beauchamp (1995) Morvan et al. (1997)
6.2
1.3
Pig
7.4 18.4
1.46
Pasture, 27 d
41
16
57
Chadwick et al. (1998)
7.2
1.8
Pig
72.8
1.25
Pasture, 30 d
16
31
47
Sørensen and Jensen (1998)
6.8, 7.0 1.4, 0.4
Sheepb
23.8
4.58, 5.31
Barley + ryegrass, 89 d
8–59c, 33–88, 81–100, 16–60c 23–68 67–88
Jensen et al. (2000)
6.0
Cattle
15.8
2.31
Wheat, 205 d
32
Mun˜oz et al. (2003)
6.7
Petersen (2005)f
6.1
2.6 2.0
Cow Pig
22.4 7.5 13.4
e
3.22
45d e
24
e
77 41e
Corn, maturity
17
Wheat, 40–65 d
31–55
31–55
Weeds
3–30
3–30 Continued
ARTICLE IN PRESS
Gutser and Dosch (1996) 6.5
7.6 20
Table 13 Recovery of 15N-labeled animal waste slurries in crops and soil in lysimeter and field experiments.—Cont’d Soil Slurry N added Reference
pH
Total N (g kg21) Type
Sørensen and Thomsen (2005b)
6.8
1.7
Powell et al. (2005) (year 2000 crop)
6.7
Pig
pH
g m22
15 N (atom%)
10.2g, 9.2h
1.1g, 3.1h
g
h
g
15
N recovery (%)
Crop and duration
Crop
Soil
Total
Spring barley, 77 d
33, 47 53, 32 86, 79
h
12.3 , 12.1 1.11 , 1.51 Winter wheat, 324 d 40, 52 39, 21 79, 73 1.64i
30.4j
1.10j
Cattle 7.2 16.3
2.17
Barley, 54 d
45–68
45–68
Cow
17–27
0.9–1.4
Maize, maturity
10–24
10–24
Hoekstra et al. (2010)
Cattle
8.3–11.0
1.8–2.7
Pasture, 60–150 df,l
18–45 20–36 38–81
Hoekstra et al. (2011)
Cattle
19–21
0.6–1.1
Pasture, 434 d
Cow
13–17
0.5
Maize, maturity
25–33
5.37
Pasture, 56 d
20–29 40–43 60–71
Petersen (2006)
f
Cusick et al. (2006a)
6.7 k
6.7
Powell et al. (2017)
6.9
Park et al. (2018)
5.7
a
2.0
1.4
Cow
Pig
5–7 20
Eight cuts, mean of two watering regimes. Fecal N slurry (no urine). c Slurry was incorporated, injected or surface-applied. d Includes 5% NH4 + + NO3 . e 1998 crop. f Slurry was incorporated or banded. g Labeled feces + unlabeled urine. h Labeled urine + unlabeled feces. i Forage method. j Urea method. k Range of values are for years 1998–2003 inclusive. l Three cuts (May to early Sept., Spring application); two cuts (July to early Sept., Summer application). b
Maize, maturity
15
45
60
16
45
60
17–50 45–72
ARTICLE IN PRESS
23.8i
2.0
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
29
mixing (incorporation), simulated injection and surface and sub-surface banding. Slurries were generally artificially enriched by adding 15 NH4 + or CO (15NH2)2 to unlabeled slurry, although several studies were carried out with naturally labeled slurries obtained by feeding 15N-enriched herbage (Hoekstra et al., 2011; Sørensen and Jensen, 1998; Sørensen and Thomsen, 2005b) or unlabeled herbage drizzled with 15N-labeled urea solution (Hoekstra et al., 2011). Slurries composed of labeled feces + unlabeled urine or unlabeled feces + labeled urine were employed in some studies (Hoekstra et al., 2011; Sørensen and Thomsen, 2005b). Total recoveries in crops and soil were quite variable, but generally ranged between 40% and 80% (Table 13). The method of application illustrated the importance of contact between slurry and soil with greater plant recoveries for simulated slurry injection compared with mixing or surface application (Sørensen and Jensen, 1998), results consistent with the pot studies of Sørensen and Jensen (1995b) and Chadwick et al. (2001). For surfacebanded pig slurry, the recovery of labeled urinary N by 324-d winter wheat in 2002 was greater than that of labeled fecal N (52% vs 40%), while the recovery in the 0–40 cm soil depth was the opposite (21% vs 39%), resulting in similar total recoveries of 73% vs 79% (Sørensen and Thomsen, 2005b). On the other hand, Hoekstra et al. (2011) found that total slurry N in herbage and soil over two growing seasons was 45% for urine and 72% for feces, indicating less N losses from feces compared to urine over a longer time period. Slurry pH had no effect on recoveries of pig slurry labeled with 15 N-urea in herbage and soil at day 56 (Park et al., 2018). Powell et al. (2005) found that total recoveries of slurry in a corn crop + soil totaled 45% for both the forage method and the urea method in 2000 (Table 13), while in 1999 the recoveries were 46% and 49%, respectively. Such consistent results across years and methods provide strong evidence for the efficacy of natural labeling techniques that require passage of the isotope through the animal digestive system.
5. Relative efficiencies of 15N-labeled excreta and 15N-labeled synthetic fertilizer The recovery of labeled synthetic fertilizers in crops and soil has been compared with recoveries of the labeled components of excreta (feces, urine, slurry) in several studies (Table 14). Recoveries of labeled fertilizer in crops were consistently higher than recoveries of labeled feces or slurry, but differences were considerably less between labeled urine and fertilizer (Table 14).
Table 14 Relative efficiency of
15
N-labeled excreta and Soil
15
N-labeled synthetic fertilizer. N added
15
N recovery (%)
15
Total pH N (g kg21) Typea
N g m22b (atom%) Crop and duration
Trehan and Wild (1993)
6.1 0.9
CoS
(0.29)
8.16d
AS
(0.25)
8.16
SF
8.7
3.93
Barley + ryegrass, 18 months 24a
76–83a 100
AS
9.0
10.37
65b
32–40b 100
CoS
10.0
5.10
AS
10.0
4.62
CoSe
(0.92)
1.43d
(0.25)
1.50
SU
20.5
3.28
U
20.0
SU U
Sørensen et al. (1994b) (three soils) 8.0 1.8
Paul and Beauchamp (1995)
Sørensen and Jensen (1995b)
2.1
6.8 1.4
7.0 0.4
6.8 1.4
Dosch and Gutser (1996)
Thomsen et al. (1997)
6.4 1.2
6.7 1.1
6.9 1.4
Maize, field, 155 d
Totalc
21
56
77
67
23
90
15a 29b 56a
37a
93a
84b
15b
99a
51a
16a
67a
4.56
53a
13a
66a
20.5
3.28
62A
36A
98A
20.0
4.56
78B
19B
97A
CoS
(2.9)
14.4
d
52a
31a
83a
AS
(2.9)
14.4
67b
31a
98b
SS
12.0
f
AS
6.0
AS Sørensen and Jensen (1996)
Potato, 98 d
Cropc Soilc
e
SS
12.0
AS
6.0
f
3.81
Ryegrass, 6 months
Ryegrass, 162 d
Oats, flowering
Barley, 100 d
22
g
5.0
36
3.81
25g
5.0
49
ARTICLE IN PRESS
Reference
Sørensen and Jensen (1998)
7.0 0.4
SSe
11.9
4.58
e
12.1
e e
AS 6.8 1.4
SS
AS Jensen et al. (1999)
5.7 1.4
SF
6.2 1.3
6.8 1.7
77a
5.36
56b
23b
79a
11.9
4.58
8A
79A
87A
12.1
5.36
53B
36B
89A
19.4
4.41
74a
93
18.8
3.62
32b
55b
87
5.0
51c
36c
87
19.4
4.41
9A
66A
75
18.8
3.62
29B
50B
79
5.0
49C
32C
81
A N 7.3
SU
Sørensen and Thomsen (2005b)
60a
15
SF 15
17a
15
A N 7.3
PF
h
Barley 120 d + 1 cut ryegrass 9a
10.2
1.10
Barley, 120 d
PUh
9.2
1.31
47b
AN
7.5
5.52
56c
ARTICLE IN PRESS
SU 15
Barley + ryegrass, 90 d
33a
a
CoS, cow slurry; AS, ammonium sulfate; SF, sheep feces; SU, sheep urine; U, urea; SS, sheep slurry; AN, ammonium nitrate; PF, pig feces; PU, pig urine. Data in parentheses are g N kg –1 soil. c Data within a column followed by different lower- or upper-case letters are significantly different (P < 0.05). d 15 N abundance of the NH4+ fraction of the slurry. e Incorporated. f Two slurries were used; 15N-labeled feces (4.41 atom% 15N) + unlabeled urine and 15N-labeled urine (3.22 atom% 15N) + unlabeled feces. The value for the abundance of the slurry is the weighted mean. g Weighted mean recoveries from labeled feces and labeled urine. h Components of slurry. Labeled feces were mixed with unlabeled urine and labeled urine was mixed with unlabeled feces. b
15
N
ARTICLE IN PRESS 32
Phillip M. Chalk et al.
In two studies, crop and soil recoveries of ammonium nitrate (AN) were compared with both feces and urine ( Jensen et al., 1999; Sørensen and Thomsen, 2005b). Recoveries in crops were in the order of feces < urine < AN, while soil recoveries were in the order feces > urine > AN. Recoveries in crops reflect the relative availability of the organic and inorganic components of animal excreta compared with the readily available N in synthetic fertilizer. Recoveries in soil were therefore consistently greater for feces and slurry compared with synthetic fertilizer, while the differences between urine and synthetic fertilizer were less marked (Table 14). However, caution needs to be exercised when comparing recoveries of uniformly labeled fertilizer with non-uniformly labeled animal excreta. Of particular concern is the form in which the 15N enrichment of the excreta is expressed, i.e., as total or a fraction of the total N in the excreta, as in the case of 15 NH4 + or 15N-enriched urea added to unlabeled urine or slurry.
6. Interactions between synthetic fertilizer N and animal excreta N Several types of experiments have been reported. Either the N fertilizer (Table 15) or the animal excreta (Table 16) can be labeled with 15 N while the other component is unlabeled. Various N fertilizer forms and types of animal excreta have been employed, and the scale of experimentation has varied among pots, lysimeters and field microplots. The simplest design has involved a comparison of a single rate of N fertilizer with and without the addition of a single rate of animal excreta. In this case the treatment comparison involves different amounts of total N addition although the amount of excess 15N added in the two treatments is the same. In order to avoid this perceived design imperfection several authors (e.g., Lee and Choi, 2017; Li, 2013; Wu et al., 2010) adjusted the ratios of fertilizer and excreta to obtain the same amounts of total N addition. However, this latter approach can result in different amounts of 15N-labeled material (N fertilizer or excreta) between treatments which invalidate treatment comparisons of 15N recoveries in plant and soil (e.g., Lee and Choi, 2017; Li, 2013). In contrast, Wu et al. (2010) achieved the same total N input (fertilizer alone, excreta alone or fertilizer + excreta; 0.15 g N kg1 soil) and the same 15 N-labeled N input (fertilizer or excreta) by maintaining the same percentages of labeled and unlabeled components of the fertilizer or the fertilizer + excreta (e.g., 60% labeled fertilizer + 40% unlabeled fertilizer cf. 60% labeled fertilizer + 40% unlabeled excreta).
Table 15 Recoveries of
15
N-labeled fertilizers in crops and soil in the presence and absence of unlabeled animal excreta. 15 Soil Fertilizer Excreta N recovery (%)
Reference
pH g N kg21 Typea
15 N g N m22b (atom%)
Typec g N m22b
Pomares-Garcia and Pratt (1978)
6.9 0.35
(0.20)
CF
21.6
Barley (229 + 64 d)e
71
18
89
72
18
90
See footnotef
Ryegrass, 5 cuts
49a
0
Ryegrass, 1st cut
52a
92 6.0 9.2
f
15
15
A N 4
2.4
PS
5.9 11.4f Stevens et al. (1987)
0
5.8 6.5
CN
5.0
2.37
CoS
2.5 5.0 Thomsen and Kjellerup (1997)
Li et al. (2001)
Lundga˚rd soil
6.6 1.7 6.9 5.6
Thomsen (2005)
1.2
15
15
A N 5.0
AS
15
5.0
10.97
g
CF
AN
0.6
99.0
61b
47a 54a
0
Barley 1993
34a
12
Spring CM
32a
0
Barley 1994
25A
12
Autumn CM
17B
Barley (maturity)
lost
26a
9
37b 46
Barley, 130 d
35a
FYM 0 45
15
Cropd Soild Totalc,d
ARTICLE IN PRESS
Stevens et al. (1986)
AS
Crop and duration
FYM 0 28
42b Continued
Table 15 Recoveries of
15
N-labeled fertilizers in crops and soil in the presence and absence of unlabeled animal excreta.—Cont’d 15 Soil Fertilizer Excreta N recovery (%)
Reference
pH g N kg21 Typea
15 N g N m22b (atom%)
Typec g N m22b
Crop and duration
Wu et al. (2010)
5.0 0.9
(0.15)
RF
Rice, 4 months 27a
AS
42.1
7.3 1.3
0
Nannen et al. (2011)
6.2 1.6 1.9
h
5.5
15
A N 16.0
3.1
CoF
24b
40b 64b
0
49A
31A 80A
44B
41B 84B
Maize (maturity)
54a
31a
86
60a
29a
89
Maize (maturity)
55a
Pasture, 554 d 60
20
80a
80 A
55
17
74b
80 S
62
17
81a
0
h
8.8 15
A15N 5.0
1.43–3.84 CS
h
0 7–15
Buckthought et al. (2015a) 5.9 6.7
a
U
40
5.0
CoU 0
60b
AS, ammonium sulfate, AN, ammonium nitrate, CN, calcium nitrate; U, urea. Data in parentheses ( ) are g N kg– 1 soil (pot experiment); A, autumn; S, spring. CF, cattle feces; PS, pig slurry; CoS, cow slurry; FYM, farmyard manure; RF, rabbit feces; CoF, cow feces; CS, cattle slurry; CoU, cow urine. d Data within a column and soil type followed by different lower- or upper-case letters are not significantly different (P < 0.05). e Two harvests of barley (71 + 158 d), followed by Sudan grass harvested after 64 days; Rates of fertilizer and excreta were the highest of each of four rates. f Plots had been fertilized with low and high (8) rates of pig slurry for 8 years previously. g Plots had been fertilized with either 0 or farmyard manure for 9 years previously. h Plots had received cow feces at either 0 or 8.8 kg N ha1 y1 for 26 years between 1977 and 2003. b c
59a
ARTICLE IN PRESS
Nyiraneza et al. (2010)
15
32a
(0.06)
(0.06) h
Cropd Soild Totalc,d
Table 16 Recoveries of
15
N-labeled animal excreta in crops and soil in the presence and absence of unlabeled N fertilizer. 15 N recovery (%) Soil Excreta Fertilizer g N kg21 Typea g N m22b
Reference
pH
Wu et al. (2010)
5.0e 0.9e
RF
(0.15)
15
N (atom%) Typec g N m22b Crop and duration Cropd Soild Totald
19.4
AS
Nannen et al. (2011)
5.5
CS
7.2–14.8 0.73
AN
8a
69a
(0.09)
12b
51b 63b
0
15A
68A 83A
(0.09)
25B
65A 90B
0
Rice, 4 months
Maize (maturity)
5.0 Buckthought et al. (2016) 5.6
CoU 80
5.0
U
0
Pasture, 106 d
RF, rabbit feces; CS, cattle slurry; CoU, cow urine. Data in parentheses ( ) are g N kg –1 soil (pot experiment). AS, ammonium sulfate; AN, ammonium nitrate; U, urea; d Data within a column and soil type followed by different lower- or upper-case letters are significantly different (P < 0.05). e Sandy soil. f Clayey soil. b c
21a 20a
3.5 a
77a
50
33
83
52
21
73
ARTICLE IN PRESS
7.3f 1.3f
0
ARTICLE IN PRESS 36
Phillip M. Chalk et al.
Interactions have been studied with respect to several variables, including type of crop, rates of addition of N fertilizer or excreta and method and time of application of fertilizer and excreta. Interactions are examined with respect to recoveries of 15N in crops and soil (Tables 15 and 16).
6.1
15
N-labeled fertilizer + unlabeled excreta
Significantly greater recoveries of labeled ammonium sulfate fertilizer were found in pot-cultured rice in the absence of unlabeled rabbit feces, whereas recoveries in soil and total recoveries were significantly greater in the presence of feces (Wu et al., 2010; Table 15). This result was consistent across two soil types (acidic and low N, alkaline and high N). A possible explanation for such a result is stimulated microbial activity and hence greater immobilization of synthetic fertilizer in the presence of feces. A similar conclusion was reached by Di et al. (1999) where marked differences were found in leaching losses between an 15 NH4 + treatment (15–19%) compared with 5–8% in a slurry (dairy shed effluent) + 15 NH4 + treatment in a lysimeter experiment, although similar plant (perennial ryegrass + white clover) recoveries of 15N between treatments were found. On the other hand, Thomsen (2005) reported that addition of farmyard manure (FYM) in a lysimeter experiment did not affect immobilization or leaching of labeled ammonium nitrate, while FYM stimulated recovery of fertilizer by barley. Similarly, Nannen et al. (2011) found that the recovery of labeled ammonium nitrate by maize was significantly higher through addition of cow slurry (Table 15). Labeled fertilizer recoveries have been measured in plots where total soil N had increased significantly through low and high annual application rates of pig slurry for 8 years (Stevens et al., 1986), farmyard manure for 9 years (Li et al., 2001) or cow feces for 26 years (Nyiraneza et al., 2010). Plant recovery of labeled fertilizer was significantly higher at the higher compared with the lower rate of pig slurry (Stevens et al., 1986), while there were no significant differences in fertilizer recovery in maize or soil in the long-term cow feces plots (Nyiraneza et al., 2010). On the other hand, Li et al. (2001) reported significantly higher fertilizer recoveries in soil in +FYM plots compared with FYM plots, a result consistent with that of Wu et al. (2010). Several authors have reported that addition of feces or slurry had no effect on the recovery of labeled fertilizer by crops (Pomares-Garcia and Pratt, 1978; Stevens et al., 1987). Similarly, Thomsen and Kjellerup (1997) found that spring feces addition had no effect on recovery of labeled ammonium
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
37
nitrate by barley, but recovery was significantly less in the presence of feces when applied in the autumn. These results were consistent across two sites (Lundga˚rd and Ashkov). Buckthought et al. (2015a) similarly reported that the total recovery of urea in crops and soil was significantly less in the presence of cow urine applied in autumn compared with a spring application. The effects of animal excreta on the recovery of synthetic fertilizer N by crops have therefore been shown to be inconsistent, with either no effect or a positive or negative effect. The rate of excreta addition had little or no effect on N fertilizer recovery in crops and soil (Pomares-Garcia and Pratt, 1978; Stevens et al., 1987) while autumn application of excreta had a negative effect compared application in spring.
6.2
15
N-labeled excreta + unlabeled fertilizer
Fewer studies have been carried out with 15N-labeled excreta + unlabeled fertilizer (Table 16) compared with 15N-labeled fertilizer + unlabeled excreta (Table 15). The recovery of labeled rabbit feces by rice in two soils was significantly enhanced by the presence of N fertilizer (Wu et al., 2010; Table 16). On the other hand, the recovery of 15N-labeled feces in the soil was either not affected or was significantly reduced by the presence of N fertilizer. Overall, there was no consistency between the soils in the total recovery of the labeled excreta, either being greater or less in the presence of the N fertilizer (Table 16). In contrast, both Nannen et al. (2011) and Buckthought et al. (2016) found no effect of N fertilizer on the recovery of slurry N or urine N in maize or pasture, respectively (Table 16), whereas Buckthought et al. (2016) found greater recovery of labeled urine N in the soil in the absence of N fertilizer. Thus there was no consistency across soils and types of excreta in the interactions between labeled excreta and unlabeled fertilizer N.
7. Losses of N from excreta-amended soils 7.1 As ammonia and nitrous oxide emissions Losses of 15NH3 can occur during storage of labeled slurry before soil application (e.g., Beline et al., 1998). However, only direct measurements of 15 NH3 volatilization from labeled excreta added to soil are considered here. The 15NH3 volatilized from soil-applied labeled slurry may represent only a temporary loss from the soil-plant system, because a part of the loss can be reabsorbed by a plant canopy (Sommer et al., 1993).
ARTICLE IN PRESS 38
Phillip M. Chalk et al.
Similarly, although losses of N2O can occur during storage of slurry (e.g., Beline et al., 2001) only losses attendant on soil addition of excreta are considered. A review of the use of both 15N enriched and 15N natural abundance techniques to estimate N2O losses from excreta-amended soils was given by Clough et al. (2013). Studies of gaseous losses of N from labeled excreta-amended soils have been concerned almost exclusively with urine (Section 7.1.1) and slurry (Section 7.1.2). In a laboratory study with labeled feces, Ingold et al. (2018) were able to differentiate labeled NH3 and N2O from unlabeled soil sources, although quantitative recoveries of the labeled gases were not recorded. In a lysimeter experiment with labeled feces and labeled urine applied individually at the same rate (100 g N m2), Wachendorf et al. (2008) found that loss of 15N2O from urine (0.05%) was less than that from feces (0.33%) over 171 d. 7.1.1 Urine The recoveries of 15N-labeled animal urine as NH3 and N2O in laboratory, pot, lysimeter and field experiments are given in Table 17. The majority of studies were conducted with synthetic or cow urine. All but one of the soils were acidic. Generally mineral soils were used, although Clough et al. (1996, 1998) also included peat soils in their lysimeter experiments. Rates of urine N addition were commonly within the range of 50–100 g N m2, although lesser amounts were sometimes applied (Table 17). NH3 losses peaked within a few days following urine application, and 15 N recoveries were quite variable (0.7–38%). NH3 loss was directly related to soil pH (Clough et al., 2003). NH3 loss was reduced when a urease inhibitor (Agrotain) was combined with the urine (Menneer et al., 2008), but the application of two nitrification inhibitors (DCD, 4MP) had no effect. NH3 volatilization loss was also reduced by addition of biochar to soil (Taghizadeh-Toosi et al., 2012). Recoveries of urine as N2O varied from trace amounts (0.02%) to very low emissions (2%), whereas only in one case (Bertram et al., 2009) were uncharacteristically high recoveries recorded. N2O losses were reduced by the addition of the nitrification inhibitor DCD (Di and Cameron, 2008) and by the addition of biochar (Taghizadeh-Toosi et al., 2011). 7.1.2 Slurry The recoveries of 15N-labeled animal waste slurries as NH3 and N2O in pot, lysimeter and field experiments are given in Table 18. The soils used were acid to neutral and varied in total N from 1.2 to 3.6 g kg1 soil. Slurries were
Table 17 Recovery of 15N-labeled animal urine as NH3 and N2O in laboratory, pot, lysimeter and field experiments. 15 Soil Urine N addeda N recovery (%) 15 N Rate 22 (g m ) (atom%)
pH
Total N (g kg21)
Type
Bronson et al. (1999)
5.0
0.72
Sheep 20.5
Clough et al. (2003)
4.7
Reference
Crop
NH3 trap (d)
NH3
N2O
None
0–28
38
0.6b
0–12
1.2
0.4, pH 5.8–6.8
0–15
7.9
Laboratory studies
50
7.7
<2
Clough et al. (2004)
4.7
Synt
50
Bertram et al. (2009)
5.9
Cow 75
5.6–5.9
0–17
17
Taghizadeh-Toosi et al. (2012)
5.5
Cow 50.9
20
0–29
1.4, 0.8d
0–7
1.4–5.3 0.8
6–17c
Pot studies Monaghan and Barraclough (1993)
6.2
Ambus et al. (2007)
5.6
Uchida et al. (2011)
5.6
3.7
Cow Synt
6.6
Pasture 26, 51
Cow 59
5.2
Pasture
0.2, 0.3
1.00
Ryegrass
0.1–1.4e Continued
ARTICLE IN PRESS
Synt
2.0
Table 17 Recovery of 15N-labeled animal urine as NH3 and N2O in laboratory, pot, lysimeter and field experiments.—Cont’d 15 Soil Urine N addeda N recovery (%) Reference
15 N Rate 22 (g m ) (atom%)
Crop
NH3 trap (d)
NH3
5.0
Pasture
0–21
2.0
50
2.0
Pasture
0–4
0.2
100
4.81
Pasture
0–4
0.7–3.9 0.8–1.9
0–20
5g–17
pH
Total N (g kg21)
Type
5.3
2.0
Cow 100 Synt
N2O
Lysimeter studies Di et al. (2002)
Clough et al. (1996) (three soils)f 4.9–5.5
1.0–1.5
Clough et al. (1998) (four soils)
5.3–6.2 4.5–18.5 Synt
Menneer et al. (2008)
6.0
4.2
Cow 77.5
4.65
Pasture
Di and Cameron (2008)
5.8
2.0
Cow 100
5.0
Pasture
0.1h–0.4
2.3
Cow 103
1.58
Ryegrass
0.05
6.7
Cow 20, 40
5.0
Pasture
<0.04
Cow 70
5.0
Pastures
0.5–1.0
Buckthought et al. (2015b)
5.9
Woods et al. (2017)
5.7
Carey et al. (2017)
6.1
4.0
Cow 35, 70
9.0
Ryegrass 0–30
3–4
6.2
3.4
Cow 74.4
4.37
Grass
17.8
1.1
Cow 6.1, 7.5 0.87–1.02 Ryegrass 0–4
1.0–2.6 12, 14
0.9
Field studies Whitehead and Bristow (1990) Leterme et al. (2003) Bol et al. (2004)
5.5
Cow 23, 40
10.2, 17.4 Pasture
Taghizadeh-Toosi et al. (2011)
5.5
Cow 93
4.96
a
Synt, synthetic urine. Includes NO emissions. c Day 53 for N2O. d Without and with biochar, respectively. e Soil temperature range 11–23 °C. f Peat soils (10 and 20 y under pasture), mineral soil (50 y pasture). g +urease inhibitor (Agrotain). h +nitrification inhibitor (DCD). b
Pasture
0–16
0–6
0.02 0.2, 0.1d
ARTICLE IN PRESS
Wachendorf et al. (2008)
<0.07
Table 18 Recovery of 15N-labeled animal waste slurry as NH3 and N2O in pot, lysimeter and field experiments. Soil Slurry N added Reference
pH Total N (g kg21) Type
pH Rate (g m22)
15
15
N recovery (%)a
N (atom%) Crop
NH3 trap (d) NH3b
14.4
0–6
N 2O
Pot studies Cattle
7.0
Wheat
50 (S)
ARTICLE IN PRESS
Dosch and Gutser (1996) 6.4 1.2
30 (I) Chadwick et al. (2001)
1.7
Pig
8.5 2500
8.31
Grass
0–8
15 (S) 11 (I)
Lysimeter studies Carey et al. (1997) Lee et al. (2014)
3.6 Not specified
Pig Cow
7.5 20, 40 27.7
9.1c
Pasture
0–14
26, 15
Barley
0–4
4
0.41
d,e
0.43
e,f
30
0.43
e,g
2
0.40
e,h
35 Continued
Table 18 Recovery of 15N-labeled animal waste slurry as NH3 and N2O in pot, lysimeter and field experiments.—Cont’d 15 Soil Slurry N added N recovery (%)a Reference
pH Total N (g kg21) Type
pH Rate (g m22)
15
N (atom%) Crop
NH3 trap (d) NH3b
N 2O
Field studies Chadwick et al. (1998)
7.2 1.8
Pig
66
0.98i
Grass
Dittert et al. (2001)
6.0
Dairy 7.5 6.4
1.45j
Pasture
Dittert et al. (2005)
5.0 2.3
Cattle
8.2
0.73
Pasture
Lampe et al. (2006)
5.0 2.3
Cattle
7.4
0.72
Pasture
<0.1
Senbayram et al. (2009)
5.0 2.3
Cattle
48
Pasture
0.4
Park et al. (2018)
5.5 1.6
Pig
5.0 a
Data in parentheses are % of ammoniacal-N. S, surface application; I, injected (shallow). Total N; 10.25 atom% of ammoniacal-N. d High protein diet, feces component of slurry 15N enriched. e Relative values (%) were converted to absolute values (Chalk et al., 2015). f High protein diet, urine component of slurry 15N enriched. g Low protein diet, feces component of slurry 15N enriched. h Low protein diet, urine component of slurry 15N enriched. i Total N; 1.25 atom% of ammoniacal-N. j Total N; 4.29 atom% of ammoniacal-N. k Low value (+DMPP), high value (DMPP). b c
5.37
32 (52) 0.8 (1.4) 0.8–1.5k
0–5
Ryegrass 0–56
4
1.1
0.05
0.8
0.03
ARTICLE IN PRESS
7.0 20
0–8
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43
from pigs and cattle, and were generally alkaline in pH (Tables 12, 13, and 18) which favors NH3 volatilization. Rates of applied slurry were generally <100 g m2, although an excessively high rate of 2.5 t ha1 was recorded by Chadwick et al. (2001). Recoveries of slurry as ammonia were low to high (<1–50%) and the peak loss generally occurred within a few days following slurry application. Higher losses were recorded for surface-applied slurry cf. injected (Chadwick et al., 2001; Dosch and Gutser, 1996), while volatilization was less for slurry adjusted to pH 5 with acid cf. pH 7 (Park et al., 2018). The percentage NH3 loss decreased as the rate of slurry application increased (Carey et al., 1997), although the total amounts volatilized (5–6 g N m2) were similar. Using slurry where the uniformly labeled component was either the feces or the urine, Lee et al. (2014) found that NH3 was more readily volatilized from the urine than from the feces, a result that was consistent for both low and high protein diets (Table 18). For slurry that was not uniformly labeled, the 15N recovered as NH3 depended on whether the calculation was made on the 15N enrichment of the total- or ammoniacal-N (Chadwick et al., 1998; Table 18). Recoveries of slurry as N2O varied from trace amounts (<0.1%) to very low emissions (maximum 4%). Therefore, in terms of the efficiency of slurry as a fertilizer, losses as N2O were orders of magnitude less than potential losses of NH3. However, whereas NH3 may be reabsorbed by foliage or redeposited in precipitation, N2O is lost to the atmosphere as a potent greenhouse gas, representing an environmental threat rather than an agronomic loss. Acidification of slurry reduced N2O emissions (Park et al., 2018), while emissions were also reduced through the use of a nitrification inhibitor, DMPP (Dittert et al., 2001).
7.2 As nitrate and ammonium in leachates Lysimeters have been used to obtain quantitative estimates of leaching losses of excreta N. The majority of studies have been carried out with 15N-labeled urine added to pasture swards (Table 19), although in a few cases labeled feces or slurry were used (e.g., Di et al., 1999; Thomsen et al., 1997). Experimental conditions were quite variable. Both natural cow urine and synthetic urine have been used with N application rates varying by more than 10-fold, from as little as 10.5 to as high as 137 g N m2. Urine 15N abundance varied between 1 and 5 atom%. Soil texture varied from coarse (loamy sand), coarse to medium (sandy loam), medium (loam) and medium to fine (silt loam, clay loam). The lysimeters varied in depth from 0.15 to 1.2 m. and the water
Table 19 Recovery (R) of
15
N-labeled animal urine in leachates in pasture-based lysimeter experiments. Soil Urine N added Text
McLaren et al. (1993)
sil
Fraser et al. (1994)
sil
Pakro and Dillon (1995)
sal
pH
5.8
Total N (g kg21)
2.6
Clough et al. (1996) Clough et al. (1998)
7–18.5
Silva et al. (2000)
sal
5.3
Di et al. (2002)
sal
5.3
Decau et al. (2003) (3 soils, 2 years)
Depth (m)
H2Ob (mm)
Typec g m22
Atom% 15 N
Durationd
R (%)
1.2
700
Synt
50
5.0
1y
16, 3e
1.2
1600
Synt
50
5.37
1y
8
0.15
349
Cow 109
0.97
84 d W
62
0.45
518
89
1.57
297 d Sp
13
0.15
83
137
1.17
80 d Su
54
0.30
615
Synt
50
2.0
150 d
3–52f
0.50
1583
Synt
100
4.81
406 d
13–32g
0.70 2.0
0.70
2.4, 2.0, 1.2 0.40
Decau et al. (2004)
cl
8.0
2.4
0.90
Silva et al. (2005)
l
5.3
2.0
0.70
0.3, 12h
Cow 100 600i
Cow 100
5.0
365 d
6, 9j
752, 803
Cow 52
2.84
2y
9, 15, 1k
Cow 10.5, 16.5 1.5, 2.84 2 y
0.1–27l, 0.1–22l
Cow 100
6
1162
5.0
1y
ARTICLE IN PRESS
Reference
a
Wachendorf et al. (2005)
5.9
2.7
0.80
810, 967
Cow 103
1.59
2y
64, 53
ls
6.0
4.2
0.45
663
Cow 77.5
4.65
196 d
15–24
Shepherd et al. (2010)
sil
5.9
5.6
0.50
804
Cow 50
5.16
247 d
15
Welten et al. (2013)
sal
5.9
8.8
0.60
1040
Synt
4.65
300 d
22
Woods et al. (2017)
sal
5.7, 6.3
0.70
1252
Cow 70
5.0
17 months 24, 17, 53m
Carey et al. (2017)
sil
6.1
4.0
0.70
560
Cow 35, 70
9.0
76–96 dn
31–32n, 28–33n
Carey et al. (2018)
sil
6.1
4.0
0.50
233
Cow 35
8.5
120 d
1–36o
a
60
Text, texture; sil, silt loam; sal, sandy loam; cl, clay loam; l, loam; ls, loamy sand. Precipitation + irrigation. c Synt, synthetic; N concentration of urine ranged from 5.58–15.6 g N L1 and contained from 32% to 88% NH4 + N. d Urine application in winter (W), spring (Sp) and summer (Su). e Data are for subsoiled and non-subsoiled treatments, respectively. f Range of data are for three soils (sil, sil, peat; pH 4.9–5.5) without a water table. g Range of data are for four soils (c, sil, sal, peat; pH 5.3–6.2). h Leached at 0 and 0.5 kPa suction, respectively. i Flood irrigation (100 mm 6 times at monthly intervals). j Values are for urine and urine + dairy effluent, respectively. k Data are for three soils (cl, l, sil—pH 8.0, 5.8, 6.7, respectively) each averaged over 2 years. l Range of data are for zero synthetic N fertilizer, season of application (spring, summer, autumn) and year. m Three pasture types (perennial ryegrass-white clover, Italian ryegrass, lucerne). n Treatments were oats (96 d) and Italian ryegrass (76 d), respectively. o Treatments were two temperatures, two light intensities (growth chamber), fallow or oats crop. b
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Menneer et al. (2008)
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Phillip M. Chalk et al.
applied either through natural rainfall or supplementary irrigation varied from 83 to 1600 mm. The experimental duration tended to be long, generally between 1 and 2 years, although it was as short as 80 d (Table 19). Given the variable nature of the experimentation, it is not surprising that there was a wide variation in the recovery of labeled urine in the leachates, from as little as <1% to as much as 60% of applied urine N. Leaching is highly site and season specific. Site variables affecting leaching include inter alia soil texture, structure, soil depth and pore size distribution, while seasonal variables include not only the total precipitation, but also its intensity and frequency, including natural rainfall and irrigation. Time is an independent variable. Given the high propensity for the downward movement of animal urine from surface-deposited urine patches, strategies have been devised and tested to limit the extent of leaching, including the use of C-rich substrates to enhance immobilization and urease and nitrification inhibitors. Shepherd et al. (2010) added either sawdust (9 t ha1) or sucrose (3, 12, 24 t ha1) to soil immediately following labeled urine application. While sawdust was not effective in reducing leaching, it was reduced by 27–66% in the +sucrose treatments, while at the same time pasture dry matter decreased by 16–29% compared to the urine alone treatment. Hence sucrose addition is not a practical method to reduce leaching. Menneer et al. (2008) tested the effect of a urease inhibitor [Agrotain, N-(n-butyl) thiophosphoric triamide] and two nitrification inhibitors (DCD, dicyandiamide; 4MP, 4 methylpyrazole) and a combination of Agrotain and DCD on the leaching of natural cow urine in a coarse-textured pumice soil. Nitrate leaching was reduced by 59% from 11.4 to 4.7 g N m2 in individual treatments of the nitrification inhibitors DCD and 4MP, but 58% of the DCD applied was recovered in leachate, illustrating its mobility or inability to be retained at the site of application in this soil. Short-term ammonia emissions (20 d) were reduced by 64% in the presence of Agrotain (7 g N m2 saved), but medium-term leaching losses increased in the presence of the urease inhibitor to 2.5 g N m2. When Agrotain was combined with DCD leaching losses were even higher at 4.5 g N m2. The major component of the leached N below 450 mm soil depth was NH4 + N which was driven by macropore processes and averaged 60% of the total N leached. Silva et al. (2000) also demonstrated NH4 + N leaching through macropores, and recommended that animals be removed from the pasture 2 days before irrigation to allow urine to diffuse into soil macropores and thus reduce leaching.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
47
Welten et al. (2013) also used a free-draining pumice soil to study the effect of DCD on the leaching of synthetic urine N. Mixing of DCD with urine before application or the spraying of DCD on the urine patch did not affect the urine leaching potential. Plant uptake of urine N increased by 32–60% and the leaching of nitrate, ammonium and dissolved organic N decreased in the presence of DCD, the extent depending mainly on the rate of application. DCD was itself leached resulting in the spatial separation of the nitrification inhibitor from the NH4 + N retained in the surface soil, and consequently represented an additional source of leached organic N, thus reducing the efficacy of DCD in reducing overall N leaching losses. The studies of Menneer et al. (2008) and Welten et al. (2013) have therefore demonstrated the potential role that nitrification inhibitors can play in protecting urinary N voided on pasture from leaching loss, but have at the same time highlighted the need for an effective yet immobile inhibitor. On the other hand the preliminary data of Menneer et al. (2008) have shown that while the urease inhibitor, Agrotain, can reduce NH3 volatilization the potential for leaching losses may increase, especially if combined with a nitrification inhibitor. Additional studies involving inhibitors combined with urine are therefore warranted. Another approach that has been tested in lysimeters to reduce leaching of N derived from urine is the planting of catch crops in situations where intensive winter forage grazing leads to high drainage losses (Carey et al., 2017, 2018). The sowing of an oats catch crop reduced nitrate leaching by 25% during the critical winter-spring drainage period compared with an Italian ryegrass cover crop (Carey et al., 2017), although relatively small amounts of 15N-urine were recovered by the catch crops (3–4%). Similar encouraging results were also obtained by Carey et al. (2018), who concluded that further research is needed to show that a catch crop can be sown successfully in most years at the farm paddock scale across a range of soil conditions.
8. The residual value of excreta N in crop sequences The residual value of various types of 15N-labeled excreta (feces, urine, slurry) was determined for several crops (cereals, grasses) grown in sequence (Table 20). As pointed out by Smith and Chalk (2018), the residual value of 15N-labeled fertilizer can be expressed as the percentage plant recovery of the labeled N added at the beginning of the crop sequence or
Table 20 Residual value of
15
N-labeled animal excreta in crop rotations or in sequential cuts of pasture species. Soil Excreta Plant recovery (%)a pH g N kg21 Typeb gN m22c
Reference
Thomsen et al. (1997)
2.1 6.7 1.1
CoS SS
10
N (atom%) R0
5.10
12
d
4.41, 3.22
6.9 1.4 Jensen et al. (1999)
5.7 1.4
SF
19.4
4.44
6.2 1.3 5.7 1.4
SU
18.4
3.62
6.2 1.3 Sørensen and Amato (2002)
f
6.4 1.4
PS
10.35–11.0 5.43–5.74
7.8 1.6 Sørensen (2004)g Powell et al. (2005)
6.4 1.4 6.7 2.0
Sørensen and Thomsen (2005b) 6.8 1.7
CoS
18.4
CoS
24–30
PS
9.7
0.64–1.6 0.84
R2
R3
Total
M, 42
M, 15
57
B, 22
B, 4
26
25
3
28
B + R, 8.5 R, 4.4
R, 2.0
15
9.0
3.8
1.1
14
32
3.3
1.3
37
29
3.8
1.3
34
B, 6.6
R, 2.5
B, 3.7
R, 1.9
15
4.9
1.9
3.5
1.5
12
B, 5.4–6.5 R, 1.9–2.2 B, 2.9–3.4 R, <2.0
3.4–3.7 h
e
R1a
h
M, 14–16h M, 4–8h B, 42
R, 1.8
18–23h B, 3.4
47
ARTICLE IN PRESS
Paul and Beauchamp (1995)
15
Cusick et al. (2006a)i
6.7 2.0
CoS
17–27
0.9–1.4
M, 10–24
M, 4–8
Wu et al. (2010)
5.0 0.9
RF
(0.15)
19.4
Rice, 8
Wheat, 8
16
15
5
20
Cotton, 7
21
10
38
Maize, 7
12
7
26
5
39
7.3 1.3 Primo et al. (2014)
6.7 0.5
GF
(0.10)
2.35
M, 1–3
Powell et al. (2017) a
6.9 1.4
CoS
13–17
0.5
M, 25–33
j
M, 5–6
j
M, maize; B, barley, R, ryegrass; CoS, cow slurry; SS, sheep slurry; SF, sheep feces; SU, sheep urine; BYM, barnyard manure; PS, pig slurry; RF, rabbit feces; GM, goat feces. c Data in parentheses are g N kg1 soil. d15 N abundance of the ammonium fraction of the slurry. e15 N abundance of the feces and urine fractions of the slurry, respectively. f Recovery data are means of all treatments (slurry mixed, injected, surface-applied). g Recovery data are ranges of values for all treatments (slurry mixed, injected, surface-applied). h Range of values are for years 1999 and 2000 and for the forage method and the urea method. i Range of values are for initial years 1998–2001 inclusive. j Range for four slurries. b
31–38j
ARTICLE IN PRESS
Cowpea, 8 26 j
19–34
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Phillip M. Chalk et al.
as a percentage of the residual 15N label in the soil at the beginning of each crop. The latter method corrects for the fertilizer N removed in the above-ground biomass or lost from the soil-plant system by leaching or denitrification, and is therefore not available to the subsequent crops. When losses are significant, this method of calculation is preferred to calculate the recovery of the residual N in the soil-plant system (Smith and Chalk, 2018). Olesen et al. (2004) summarized the results of experiments conducted in Denmark between 1994 and 2002, which included a range of 15N-labeled feces and urine from ruminants and pigs, either in slurry or solid feces, and applied to spring barley or winter wheat. 15N recoveries by crops in the application year were quite variable ranging from 9% to 47%, but were more consistent in the first (2.5–6%) and second (1.1–2.5%) residual years. Plant recovery of excreta N in the first (R0) and subsequent years (R1–R3) was largely dependent on the type of excreta. Recovery of sheep urine in R0 in two soils was close to 30%, decreasing to 3–4% in R1 and 1% in R2 ( Jensen et al., 1999; Table 20). The recoveries of feces N in R0 were relatively low (7–15%; Table 20), with either an increase in R1 (Primo et al., 2014) or a gradual decline in R1 and R2 ( Jensen et al., 1999), suggesting a higher residual value of feces. Compared with synthetic N fertilizers, feces had lower recoveries in R0 and R1 but higher recoveries in R2 and R3 (Smith and Chalk, 2018), reflecting the slow N release characteristics of feces. In contrast, recovery of 15N-labeled animal slurry in R0 was either high (Paul and Beauchamp, 1995; Thomsen et al., 1997) or low (Sørensen, 2004; Sørensen and Amato, 2002), which to some extent may reflect the relative proportions of feces and urine in the slurry. For example, in the study of Thomsen et al. (1997) the slurry was composed of either labeled urine + unlabeled feces or labeled feces + unlabeled urine. Crop recovery of labeled feces in R0 was 12–14% in two soils while recovery of labeled urine was 32–36%. In R1, recoveries of all labeled moieties were from 3% to 4%. The residual value of animal excreta was studied with the dynamic simulation model FAS-SET (Berntsen et al., 2007), which was validated with 1–3 years of data from three field experiments differing in several agronomic, edaphic and environmental variables. The model predicted that the type of excreta influenced the residual N value, which was reduced by wet climates, sandy soils and short-season crops, but not by the soil organic matter level.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
9. Partial
15
51
N balance
15
N balance studies involve an accounting of labeled N inputs via feces, urine or slurry and outputs comprising crop uptake, leaching of ammonium + nitrate, and gaseous emissions of NH3 and N2O as well as residual 15N excess in the soil. The added isotope which cannot be accounted for (i.e., labeled inputs—outputs) is assumed to represent losses, mainly as emission of N2, that cannot be readily measured in an open system. A tabular summary of 15N balances of labeled urine applied to swards of grasses and legumes worldwide was presented by Woods et al. (2017). The summary included data from 29 studies in 7 countries including 15N recoveries in plants, soil, leachates and gaseous NH3 and N2O losses. Of these 29 studies, 22 have been cited in the present review, with others (e.g., theses, unlabeled and 15N natural abundance studies, and labeled urea as a urine substitute) being excluded. Of these 22, we could identify only one study (Clough et al., 1998) where all inputs/outputs mentioned above were measured. Over a measurement period of 406 days with urine applied at 1000 kg N ha1 in winter to a perennial ryegrass-white clover sward, the total recoveries ranged from 68 (peat soil) to 81% (clay soil) with intermediate values for a sandy loam and a silt loam. Thus, despite the considerable effort to comprehensively measure all 15N-labeled outputs in an open field situation some 20–30% of added urine N remained unaccounted for. These findings contrast with results obtained in closed systems in which quantitative recoveries of 15N labeled fertilizer added to soils were obtained in organic, inorganic and gaseous phases both under anaerobic conditions in the laboratory (Chen et al., 1995) and aerobic conditions in the glasshouse (Clough et al., 2001).
10. Conclusions An extensive literature exists on the fate of 15N-enriched animal excreta in the soil-plant-atmosphere system, which has grown exponentially over the past 21 years since the publication of the last comprehensive review by Dittert et al. (1998). A major concern with the interpretation and comparison of data is the degree of isotopic uniformity both within and between the solid (feces) and liquid (urine) components of excreta and their admixture (slurry). Only limited attention has so far been given to the assessment of errors associated with the non-uniform distribution of isotope, particularly in urine and slurry.
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Phillip M. Chalk et al.
The feeding of 15N-enriched forage, silage or grain to animals is the best guarantee of obtaining isotopic uniformity in feces and urine, but this approach is time-consuming, complicated and expensive. For example, Powell et al. (2017) fed four 15N-enriched diets to three milking cows per diet over a period of 2–4 days which required a daily dry matter intake of 25 kg per cow. This exercise required detailed calculations of land area, amounts of 15N-labeled fertilizer, predicted crop yield, crop N uptake and N fertilizer use efficiency, in order to provide sufficient labeled materials, which varied in 15N abundance from 0.74 to 2.40 atom% 15N. The processing and storage of the feed components and the collection and storage of excreta four times per day for 4 days from individual cows added to the logistics attendant on this approach. For example, Powell et al. (2017) generated 324 15N-enriched samples of feces with an equal number of labeled urine samples. Specialized equipment such as indwelling catheters were also used to ensure separation of feces and urine (Powell et al., 2017), thus increasing the cost and degree of sophistication. Nevertheless, the use of 15N-enriched animal excreta has provided quantitative data on many of the processes that affect the use efficiency of these organic sources of N by crops and pastures. One advantage of the use of animal feces as a source of N for crop and pasture growth is its slow release characteristic. We obtained evidence that although initial recovery in a crop sequence may be less compared with a synthetic fertilizer, the residual value may be higher. Similar agronomic and environmental issues surround the use of both synthetic fertilizers and excreta as sources of N for plant nutrition, although the processes may differ in intensity both spatially and temporally. Of general concern are emissions of NH3 and N2O, and leaching of inorganic N. While losses of N2O are generally a small fraction of the N applied, and therefore of little effect on fertilizer use efficiency, they are nevertheless of great significance due to the potency of N2O as a greenhouse gas. Although there is little doubt that the use of 15N-enriched excreta to trace N dynamics in agroecosystems adds another layer of complexity to the evaluation of N use efficiency, without this technology we would not have the quantitative body of data we now possess regarding the efficacy of animal excreta as an organic N source, its losses and mitigation strategies. Only limited attention has been given to the alternative approach of using 15 N natural abundance (NA) as a tracer of animal excreta N dynamics (Chalk et al., 2019). For example, there are indications that under some conditions changes in the δ15N signature of substrates could indirectly indicate the extent of NH3 volatilization. Chalk et al. (2019) concluded that more
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
53
research is needed in this area in relation to the composting of agricultural wastes, the storage and treatment of animal excreta and animal excreta voided on pastures. While farmers can exert some control over rate, placement and timing of synthetic N fertilizer application, there is little opportunity for control of excreta deposition under conditions of extensive grazing. However, under intensive animal feeding operations there may be more scope for management of excreta in order to reduce NH3 volatilization, by modifying bedding materials (Sun et al., 2016). Because of the random deposition of excreta under extensive grazing, control of nitrate leaching from urine through the use of a nitrification inhibitor is unlikely to succeed unless it can be fed to the animal (e.g., Minet et al., 2016). The alternative use of catch crops is another little-explored possibility to reduce leaching losses under extensive systems of grazing.
Acknowledgments The authors wish to acknowledge the sustained and substantial contributions from several groups of scientists worldwide: In Denmark (e.g., Sørensen, Thomsen and colleagues at various institutions); in Germany (e.g., Dittert and colleagues at various institutions); in the United States (e.g., Powell, Kelling and colleagues at the University of Wisconsin); and in New Zealand (e.g., Cameron, Di, Clough, Sherlock, Ledgard and colleagues at Lincoln University and AgResearch), who collectively have made many outstanding contributions to this field of study.
References Abdelhamid, M., Horiuchi, T., Oba, S., 2004. Nitrogen uptake by fababean from 15Nlabeled oilseed-rape residue and chicken manure with ryegrass as a reference crop. Plant Prod. Sci. 7, 371–376. Aita, C., Recous, S., Cargnin, R.H.O., da Luz, L.P., Giacomini, S.J., 2012. Impact on C and N dynamics of simultaneous application of pig slurry and wheat straw, as affected by their initial locations in soil. Biol. Fertil. Soils 48, 633–642. Ambus, P., Petersen, S.O., Soussana, J.-F., 2007. Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling. Agric. Ecosyst. Environ. 121, 84–92. Ayadi, F.Y., Cortus, E.L., Clay, D.E., Hansen, S.A., 2015. Isotope ratio mass spectrometry monitoring of nitrogen volatilization from beef cattle feces and 15N-labeled synthetic urine. Atmosphere 6, 641–649. Barkle, G.F., Stenger, R., Brown, T.N., Ledgard, S.F., Painter, D.J., 2001. Fate of 15Nlabeled feces fraction of dairy farm effluent (DFE) irrigated onto soils under different water regimes. Nutr. Cycl. Agroecosyst. 59, 85–93. Barros, T., Powell, J.M., Danes, M.A.C., Aguerre, M.J., Wattiaux, M.A., 2017. Relative partitioning of N from alfalfa silage, corn silage, corn grain and soybean meal into milk, urine, and feces, using stable 15N isotope. Anim. Feed Sci. Technol. 229, 91–96. Beline, F., Martinez, J., Marol, C., Guiraud, G., 1998. Nitrogen transformations during anaerobically stored 15N-labeled pig slurry. Bioresour. Technol. 64, 83–88.
ARTICLE IN PRESS 54
Phillip M. Chalk et al.
Beline, F., Martinez, J., Marol, C., Guiraud, G., 2001. Application of the 15N technique to determine the contributions of nitrification and denitrification to the flux of nitrous oxide from aerated pig slurry. Water Res. 35, 2774–2778. Bergstr€ om, L.F., Kirchmann, H., 1999. Leaching of total nitrogen from nitrogen-15-labeled poultry manure and inorganic nitrogen fertilizer. J. Environ. Qual. 28, 1283–1290. Berntsen, J., Petersen, B.M., Sørensen, P., Olesen, J.E., 2007. Simulating residual effects of animal manures using 15N isotopes. Plant Soil 290, 173–187. Bertram, J.E., Clough, T.J., Sherlock, R.R., Condron, L.M., O’Callaghan, M., Well, N.S., Ray, J.L., 2009. Hippuric acid and benzoic acid inhibition of urine derived N2O emissions from soil. Glob. Chang. Biol. 15, 2067–2077. Bol, R., Petersen, S.O., Christofides, C., Dittert, K., Hansen, M.N., 2004. Short-term N2O, CO2, NH3 fluxes, and N/C transfers in a Danish grass-clover pasture after simulated urine deposition in autumn. J. Plant Nutr. Soil Sci. 167, 568–576. Bosshard, C., Frossard, E., Dubois, D., M€ader, P., Manolov, I., Oberson, A., 2008. Incorporation of nitrogen-15-labeled amendments into physically separated soil organic matter fractions. Soil Sci. Soc. Am. J. 72, 949–959. Bosshard, C., Sørensen, P., Frossard, E., Dubois, D., M€ader, P., Nanzer, S., Oberson, A., 2009. Nitrogen use efficiency of 15N-labeled sheep manure and mineral fertilizer applied to microplots in long-term organic and conventional cropping systems. Nutr. Cycl. Agroecosyst. 83, 271–287. Bosshard, C., Oberson, A., Leinweber, P., Jandl, G., Knicker, H., Wettstein, H.-R., Kreuzer, M., Frossard, E., 2011. Characterization of fecal nitrogen forms produced by a sheep fed with 15N labeled ryegrass. Nutr. Cycl. Agroecosyst. 90, 355–368. Bronson, K.F., Sparling, G.P., Fillery, I.R.P., 1999. Short-term N dynamics following application of 15N-labeled urine to a sandy soil in summer. Soil Biol. Biochem. 31, 1049–1057. Buckthought, L.E., Clough, T.J., Cameron, K.C., Di, H.J., Shepherd, M.A., 2015a. Urine patch and fertiliser N interaction: effects of fertiliser rate and season of urine application on nitrate leaching and pasture N uptake. Agric. Ecosyst. Environ. 203, 19–28. Buckthought, L.E., Clough, T.J., Cameron, K.C., Di, H.J., Shepherd, M.A., 2015b. Fertiliser and seasonal urine effects on N2O emissions from the urine-fertiliser interface of a grazed pasture. N. Z. J. Agric. Res. 58, 311–324. Buckthought, L.E., Clough, T.J., Cameron, K.C., Di, H.J., Shepherd, M.A., 2016. Plant N uptake in the periphery of a bovine urine patch: determining the ‘effective area’. N. Z. J. Agric. Res. 59, 122–140. Cameron, K.C., Rate, A.W., Carey, P.L., Smith, N.P., 1995. Fate of nitrogen in pig effluent applied to a shallow stony pasture soil. N. Z. J. Agric. Res. 38, 533–542. Carey, P.L., Rate, A.W., Cameron, K.C., 1997. Fate of nitrogen in pig slurry applied to a New Zealand pasture soil. Aust. J. Soil Res. 35, 941–959. Carey, P.L., Cameron, K.C., Di, H.J., Edwards, G.R., 2017. Comparison of nitrate leaching from oats and Italian ryegrass catch crops following simulated winter forage grazing: a field lysimeter study. N. Z. J. Agric. Res. 60, 298–318. Carey, P.L., Cameron, K.C., Di, H.J., Edwards, G.R., 2018. Does sowing an oats catch crop reduce nitrate leaching from urine deposition following simulated winter forage grazing? A growth chamber experiment. Plant Soil 431, 37–52. Carter, M.S., 2007. Contribution of nitrification and denitrification to N2O emissions from urine patches. Soil Biol. Biochem. 39, 2091–2102. Catchpoole, D.W., Blair, G.J., 1990. Forage tree legumes. III. Release of nitrogen from leaf, feces and urine derived from Leucaena and Gliricidia leaf. Crop Pasture Sci. 41, 539–547. Cavalli, D., Bechini, L., Di Matteo, A., Corti, M., Ceccon, P., Gallina, P.M., 2018. Nitrogen availability after repeated additions of raw and anaerobically digested 15N-labelled pig slurry. Eur. J. Soil Sci. 69, 1044–1055.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
55
Chadwick, D.R., van der Weerden, T., Martinez, J., Pain, B.F., 1998. Nitrogen transformations and losses following pig slurry applications to a natural soil filter system (solepur process) in Brittany, France. J. Agric. Eng. Res. 69, 85–93. Chadwick, D.R., Martinez, J., Marol, C., Beline, F., 2001. Nitrogen transformations and ammonia loss following injection and surface application of pig slurry: a laboratory experiment using slurry labeled with 15N-ammonium. J. Agric. Sci. (Camb.) 136, 231–240. Chalk, P.M., Magalha˜es, A.M.T., Ina´cio, C.T., 2013. Towards an understanding of the dynamics of compost N in the soil-plant-atmosphere system using 15N tracer. Plant Soil 362, 373–388. Chalk, P.M., Ina´cio, C.T., Magalha˜es, A.M.T., 2014. From fertilizer to food: tracing N dynamics in conventional and organic farming systems using 15N natural abundance. In: Heng, L.K., Sakadevan, K., Dercon, G., Nguyen, M.L. (Eds.), Managing Soils for Food Security and Climate Change Adaptation and Mitigation. FAO, Rome, pp. 339–348. http://www-naweb.iaea.org/nafa/swmn/public/ManagingSoilFoodSecurity ProceedingsFAO-6.pdf. Chalk, P.M., Ina´cio, C.T., Craswell, E.T., Chen, D., 2015. On the usage of absolute (x) and relative (δ) values of 15N abundance. Soil Biol. Biochem. 85, 51–53. Chalk, P.M., Ina´cio, C.T., Chen, D., 2019. An overview of contemporary advances in the usage of 15N natural abundance (δ15N) as a tracer of agro-ecosystem N cycle processes that impact the environment. Agric. Ecosyst. Environ. 283, 106570. Chantigny, M.H., Angers, D.A., Morvan, T., Pomar, C., 2004a. Dynamics of pig slurry nitrogen in soil and plant as determined with 15N. Soil Sci. Soc. Am. J. 68, 637–643. Chantigny, M.H., Angers, D.A., Pomar, C., Morvan, T., 2004b. The use of 15N-enriched feed to label pig excreta for N cycling studies. Can. J. Soil Sci. 84, 43–48. Chen, D.L., Chalk, P.M., Freney, J.R., 1995. Distribution of reduced products of 15Nlabelled nitrate in anaerobic soils. Soil Biol. Biochem. 27, 1539–1545. ., 2009. Nitrogen Clark, K., Chantigny, M.H., Angers, D.A., Rochette, P., Parent, L.-E transformations in cold and frozen agricultural soils following organic amendments. Soil Biol. Biochem. 31, 348–356. Clough, T.J., Kelliher, F.M., 2005. Dairy farm effluent effects on urine patch nitrous oxide and carbon dioxide emissions. J. Environ. Qual. 34, 979–986. Clough, T.J., Sherlock, R.R., Cameron, K.C., Ledgard, S.F., 1996. Fate of urine nitrogen on mineral and peat soils in New Zealand. Plant Soil 178, 141–152. Clough, T.J., Ledgard, S.F., Sprosen, M.S., Kear, M.J., 1998. Fate of 15N labeled urine on four soil types. Plant Soil 199, 195–203. Clough, T.J., Sherlock, R.R., Cameron, K.C., Stevens, R.J., Laughlin, R.J., M€ uller, C., 2001. Resolution of the 15N balance enigma? Aust. J. Soil Res. 39, 1419–1431. Clough, T.J., Sherlock, R.R., Kelliher, F.M., 2003. Can liming mitigate N2O fluxes from a urine-amanded soil? Aust. J. Soil Res. 41, 439–457. Clough, T.J., Kelliher, F.M., Sherlock, R.R., Ford, C.D., 2004. Lime and soil moisture effects on nitrous oxide emissions from a urine patch. Soil Sci. Soc. Am. J. 68, 1600–1609. Clough, T.J., M€ uller, C., Laughlin, R.J., 2013. Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems. Animal 7 (s2), 418–426. Cusick, P.R., Kelling, K.A., Powell, J.M., Mun˜oz, G.R., 2006a. Estimates of residual dairy manure nitrogen availability using various techniques. J. Environ. Qual. 35, 2170–2177. Cusick, P.R., Powell, J.M., Kelling, K.A., Hensler, R.F., Mun˜oz, G.R., 2006b. Dairy manure N mineralization estimates from incubations and litterbags. Biol. Fertil. Soils 43, 145–152.
ARTICLE IN PRESS 56
Phillip M. Chalk et al.
de Klein, C.M., van Logtestijn, R.S.P., 1994. Denitrification and N2O emission from urineaffected grassland soil. Plant Soil 163, 235–241. Decau, M.L., Simon, J.C., Jacquet, A., 2003. Fate of urine nitrogen in three soils throughout a grazing season. J. Environ. Qual. 32, 1405–1413. Decau, M.L., Simon, J.C., Jacquet, A., 2004. Nitrate leaching under grassland as affected by mineral N fertilization and cattle urine. J. Environ. Qual. 33, 637–644. Di, H.J., Cameron, K.C., 2008. Sources of nitrous oxide from 15N-labeled animal urine and urea fertilizer with and without a nitrification inhibitor, dicyandiamide (DCD). Aust. J. Soil Res. 46, 76–82. Di, H.J., Cameron, K.C., Moore, S., Smith, N.P., 1999. Contributions to nitrogen leaching and pasture uptake by autumn-applied dairy effluent and ammonium fertilizer labeled with 15N isotope. Plant Soil 210, 189–198. Di, H.J., Cameron, K.C., Silva, R.G., Russell, J.M., Barnett, J.W., 2002. A lysimeter study of the fate of 15N-labeled nitrogen in cow urine with or without farm dairy effluent in a grazed dairy pasture soil under flood irrigation. N. Z. J. Agric. Res. 45, 235–244. Dijkstra, J., Oenema, O., van Groenigen, J.W., Spek, J.W., van Vuuren, A.M., Bannink, A., 2013. Diet effects on urine composition of cattle and N2O emissions. Animal 7, 292–302. Dittert, K., Goerges, T., Sattelmacher, B., 1998. Nitrogen turnover in soil after application of animal manure and slurry as studied by the stable isotope 15N: a review. J. Plant Nutr. Soil Sci. 161, 453–463. Dittert, K., Bol, R., King, R., Chadwick, D., Hatch, D., 2001. Use of a novel nitrification inhibitor to reduce nitrous oxide emission from 15N-labeled dairy slurry injected into soil. Rapid Commun. Mass Spectrom. 15, 1291–1296. Dittert, K., Lampe, C., Gasche, R., Butterbach-Bahl, K., Wachendorf, M., Papen, H., Sattelmacher, B., Taube, F., 2005. Short-term effects of single or combined application of mineral N fertilizer and cattle slurry on the fluxes of radiatively active trace gases from grassland soil. Soil Biol. Biochem. 37, 1665–1674. Dosch, P., Gutser, R., 1996. Reducing N losses (NH3, N2O, N2) and immobilization from slurry through optimized application techniques. Nutr. Cycl. Agroecosyst. 43, 165–171. Fraser, P.M., Cameron, K.C., Sherlock, R.R., 1994. Lysimeter study of the fate of nitrogen in animal urine returns to irrigated pasture. Eur. J. Soil Sci. 45, 439–447. Garza, H.M.Q., Delgado, J.A., Wong, J.A.C., Lindemann, W.C., 2009. 15N uptake from manure and fertilizer sources by three consecutive crops under controlled conditions. Rev. Bras. Ci^enc. Solo 33, 1249–1258. Gutser, R., Dosch, P., 1996. Cattle-slurry—15N turnover in long-term lysimeter trial. In: Rodrigues-Barrueco, C. (Ed.), Fertilizers and Environment. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 345–350. Haynes, R.J., Williams, P.H., 1993. Nutrient cycling and soil fertility in the grazed pasture ecosystem. Adv. Agron. 49, 119–199. He, D.-Y., Xing, T.-X., Zhou, W.-J., He, L.-H., Liao, X.-L., 1992. Fate and transformation of nitrogen from 15N-labeled rice straw after feeding goat. Pedosphere 2, 161–170. He, D.-Y., Liao, X.-L., Xing, T.-X., Zhou, W.-J., Fang, Y.-J., He, L.-H., 1994. The fate of nitrogen from 15N-labeled straw and green manure in soil-crop-domestic animal systems. Soil Sci. 158, 65–73. Hoekstra, N.J., Lalor, S.T.J., Richards, K.G., O’Hea, N., Lanigan, G.J., Dyckmans, J., Schulte, R.P.O., Schmidt, O., 2010. Slurry 15NH4-N recovery in herbage and soil: effects of application method and timing. Plant Soil 330, 357–368. Hoekstra, N.J., Lalor, S.T.J., Richards, K.G., O’Hea, N., Dungait, J.A.J., Schulte, R.P.O., Schmidt, O., 2011. The fate of slurry-N fractions in herbage and soil during two growing seasons following application. Plant Soil 342, 83–96.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
57
Holbeck, B., Amelung, W., Wolf, A., S€ udekum, K.-H., Schloter, M., Welp, G., 2013. Recoveries of 15N-labeled fertilizers (chicken manure, mushroom compost and potassium nitrate) in arable topsoil after autumn application to winter cover crops. Soil Tillage Res. 130, 120–127. Ina´cio, C.T., Chalk, P.M., 2017. Principles and limitations of stable isotopes in differentiating organic and conventional foodstuffs: 2. Animal products. Crit. Rev. Food Sci. Nutr. 57, 181–196. Ina´cio, C.T., Chalk, P.M., Magalha˜es, A.M.T., 2015. Principles and limitations of stable isotopes in differentiating organic and conventional foodstuffs: 1. Plant products. Crit. Rev. Food Sci. Nutr. 55, 1206–1218. Ingold, M., Khanal, G., Dyckmans, J., Wachendorf, C., 2018. NH3 volatilization, N2O emission and microbial biomass turnover from 15N-labeled manure under laboratory conditions. Commun. Soil Sci. Plant Anal. 49, 537–551. Jayasundara, S., Wagner-Riddle, C., Parkin, G., Lauzon, J., Fan, M.Z., 2010. Transformations and losses of swine manure 15N as affected by application timing at two contrasting sites. Can. J. Soil Sci. 90, 55–73. Jensen, B., Sørensen, P., Thomsen, I.K., Jensen, E.S., Christensen, B.T., 1999. Availability of nitrogen in 15N-labeled ruminant manure components to successively grown crops. Soil Sci. Soc. Am. J. 63, 416–423. Jensen, L.S., Pedersen, I.S., Hansen, T.B., Nielsen, N.E., 2000. Turnover and fate of 15Nlabeled cattle slurry ammonium-N applied in the autumn to winter wheat. Eur. J. Agron. 12, 23–35. Kirchmann, H., 1990. Nitrogen interactions and crop uptake from fresh and composted 15Nlabeled poultry manure. Eur. J. Soil Sci. 41, 379–385. Kirchmann, H., 1991. Carbon and nitrogen mineralization of fresh, aerobic and anaerobic animal manures during incubation with soil. Swed. J. Agric. Res. 21, 165–173. Lampe, C., Dittert, K., Sattelmacher, B., Wachendorf, M., Loges, R., Taube, F., 2006. Sources and rates of nitrous oxide emissions from grazed grassland after application of 15 N-labeled mineral fertilizer and slurry. Soil Biol. Biochem. 38, 2602–2613. Langmeier, M., Frossard, E., Kreuzer, M., M€ader, P., Dubois, D., Oberson, A., 2002. Nitrogen fertilizer value of cattle manure applied on soils originating from organic and conventional farming systems. Agronomie 22, 789–800. Lee, J., Choi, H.L., 2017. The dynamics of nitrogen derived from a chemical nitrogen fertilizer with treated swine slurry in paddy soil-plant systems. PLoS One 12 (3), e1074747. Lee, C., Feyereisen, G.W., Hristov, A.N., Dell, C.J., Kaye, J., Beegle, D., 2014. Effects of dietary protein concentration on ammonia volatilization, nitrate leaching, and plant nitrogen uptake from dairy manure applied to lysimeters. J. Environ. Qual. 43, 398–408. Leterme, P., Barre, C., Vertes, S., 2003. The fate of 15N from dairy cow urine under pasture receiving different rates of N fertilizer. Agronomie 23, 609–616. Li, S., 2013. Substitution effect of pig manure for nitrogen fertilizer on nitrogen-use efficiency. Commun. Soil Sci. Plant Anal. 44, 2701–2712. Li, K., Shiraiwa, T., Inamura, T., Saitoh, K., Horie, T., 2001. Recovery of 15N-labeled ammonium by barley and maize grown on the soils with long-term application of chemical and organic fertilizers. Plant Prod. Sci. 4, 29–35. Liu, J., Xie, Q., Shi, Q., Li, M., 2008. Rice uptake and recovery of nitrogen with different methods of applying 15N-labeled chicken manure and ammonium sulphate. Plant Prod. Sci. 11, 271–277. Martı´nez-Alca´ntara, B., Martı´nez-Cuenca, M.-R., Ferna´ndez, C., Legaz, F., Quin˜ones, A., 2016a. Production of 15N-labeled liquid organic fertilizers based on manure and crop residue for use in fertigation studies. PLoS One 11 (3), e0150851.
ARTICLE IN PRESS 58
Phillip M. Chalk et al.
Martı´nez-Alca´ntara, B., Martı´nez-Cuenca, M.-R., Bermejo, A., Legaz, F., Quin˜ones, A., 2016b. Liquid organic fertilizers for sustainable agriculture: nutrient uptake of organic versus mineral fertilizers in citrus trees. PLoS One 11 (10), e0161619. McLaren, R.G., Cameron, K.C., Fraser, P.M., 1993. A comparison of the effects of subsoiling on plant uptake and leaching losses of sulphur and nitrogen from a simulated urine patch. Plant Soil 155/156, 375–378. Menneer, J.C., Ledgard, S.F., Sprosen, M., 2008. Soil N process inhibitors after nitrogen leaching dynamics in a pumice soil. Aust. J. Soil Res. 46, 323–331. Minet, E.P., Ledgard, S.F., Lanigan, G.J., Murphy, J.B., Grant, J., Hennessy, D., Lewis, E., Forrestal, P., Richards, K.G., 2016. Mixing dicyandiamide (DCD) with supplementary feeds for cattle: an effective method to deliver a nitrification inhibitor in urine patches. Agric. Ecosyst. Environ. 231, 114–121. Moal, J.-F., Martinez, J., Marol, C., Guiraud, G., 1994. A direct incorporation of N-15 labeled ammonium sulphate into a pig slurry: a laboratory experiment on NH3 volatilization. Bioresour. Technol. 48, 87–89. Monaghan, R.M., Barraclough, D., 1993. Nitrous oxide and dinitrogen emissions from urine-affected soil under controlled conditions. Plant Soil 151, 127–138. Morvan, T., Leterme, P., Arsene, G.G., Mary, B., 1997. Nitrogen transformations after the spreading of pig slurry on bare soil and ryegrass using 15N-labeled ammonium. Eur. J. Agron. 7, 181–188. Mun˜oz, G.R., Powell, J.M., Kelling, K.A., 2003. Nitrogen budget and soil N dynamics after multiple applications of unlabeled or 15nitrogen-enriched dairy manure. Soil Sci. Soc. Am. J. 67, 817–825. Mun˜oz, G.R., Kelling, K.A., Powell, J.M., Speth, P.E., 2004. Comparison of estimates of first-year dairy manure nitrogen availability or recovery using nitrogen-15 and other techniques. J. Environ. Qual. 33, 719–727. Nannen, D.U., Herrmann, A., Loges, R., Dittert, K., Taube, F., 2011. Recovery of mineral fertilizer N and slurry N in continuous silage maize using the 15N and difference methods. Nutr. Cycl. Agroecosyst. 89, 269–280. Nishida, M., Tsuchiya, K., Yamamuro, S., 2004. Fate of N and relative efficiency of 15Nlabeled organic materials applied to transplanted rice in Northern Kyushu region of Japan. Soil Sci. Plant Nutr. 50, 225–232. Nyiraneza, J., Chantigny, M.H., N’Dayegamiye, A., Lave`rdiere, M.R., 2010. Long-term manure application and forages reduce nitrogen fertilizer requirements of silage corncereal cropping systems. Agron. J. 102, 1244–1251. Olesen, J.E., Sorensen, P., Thomsen, I.K., Eriksen, J., Thomsen, A.G., Berntsen, J., 2004. Integrated nitrogen input systems in Denmark. In: Agriculture and the Nitrogen Cycle. 65, Scope, pp. 129–140. Pakro, N., Dillon, P., 1995. Preferential flow, nitrogen transformations and 15N balance under urine-affected areas of irrigated and non-irrigated clover-based pastures. J. Contam. Hydrol. 20, 329–347. Park, S.H., Lee, B.R., Jung, K.H., Kim, T.H., 2018. Acidification of pig slurry effects on ammonia and nitrous oxide emissions, nitrate leaching, and perennial ryegrass regrowth as estimated by 15N-urea flux. Asian Australas. J. Anim. Sci. 31, 457–466. Paul, J.W., Beauchamp, E.G., 1995. Availability of manure slurry ammonium for corn using 15 N-labeled (NH4)2SO4. Can. J. Soil Sci. 75, 35–42. Petersen, J., 2005. Competition between weeds and spring wheat for 15N-labeled nitrogen applied in pig slurry. Weed Res. 45, 103–113. Petersen, J., 2006. Crop 15N recovery course affected by spatial distribution of animal slurries in soils. Nutr. Cycl. Agroecosyst. 75, 15–27. Pomares-Garcia, F., Pratt, P.F., 1978. Recovery of 15N-labeled fertilizer from manured and sludge-amended soils. Soil Sci. Soc. Am. J. 42, 717–720.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
59
Powell, J.M., Wu, Z., 1999. Nitrogen-15 labeling of dairy feces and urine for nutrient cycling studies. Agron. J. 91, 814–818. Powell, J.M., Wu, Z., Kelling, K., Cusick, P., Mun˜oz, G., 2004. Differential nitrogen-15 labeling of dairy manure components for nitrogen cycling studies. Agron. J. 96, 433–441. Powell, J.M., Kelling, K.A., Mun˜oz, G.R., Cusick, P.R., 2005. Evaluation of dairy manure nitrogen-15 enrichment methods on short-term crop and soil nitrogen budgets. Agron. J. 97, 333–337. Powell, J.M., Barros, T., Danes, M., Aguerre, M., Wattiaux, M., Reed, K., 2017. Nitrogen use efficiencies to grow, feed, and recycle manure from the major diet components fed to dairy cows in the USA. Agric. Ecosyst. Environ. 239, 274–282. Primo, D.C., Menezes, R.S.C., Sampaio, E.V.S.B., Garrido, M.S., Junior, J.C.B., Souza, C.S., 2014. Recovery of N applied as 15N-manure or 15N-gliricidia biomass by maize, cotton and cowpea. Nutr. Cycl. Agroecosyst. 100, 205–214. Senbayram, M., Chen, R., M€ uhling, K.H., Dittert, K., 2009. Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers. Rapid Commun. Mass Spectrom. 23, 2489–2498. Shand, C.A., Williams, B.L., Smith, S., Young, M.E., 2000. Temporal changes in C, P and N concentrations in soil solution following application of synthetic sheep urine to a soil under grass. Plant Soil 222, 1–13. Shepherd, M., Menneer, J., Ledgard, S., Sarathchandra, U., 2010. Application of carbon additives to reduce nitrogen leaching from cattle urine patches on pasture. N. Z. J. Agric. Res. 53, 263–280. Silva, R.G., Cameron, K.C., Di, H.J., Smith, N.P., Buchan, D.G., 2000. Effect of macropore flow on the transport of surface-applied cow urine through a soil profile. Aust. J. Soil Res. 38, 13–24. Silva, R.G., Cameron, K.C., Di, H.J., Jorgensen, E.E., 2005. A lysimeter study to investigate the effect of dairy effluent and urea on cattle urine N losses, plant uptake and soil retention. Water Air Soil Pollut. 164, 57–78. Smith, C.J., Chalk, P.M., 2018. The residual value of fertiliser N in crop sequences: an appraisal of 60 years of research using 15N tracer. Field Crop Res. 217, 66–74. Sommer, S.G., Jensen, E.S., Schjørring, J.K., 1993. Leaf absorption of atmospheric ammonia emitted from pig slurry applied beneath the canopy of winter wheat. Acta Agric. Scand. B. Soil Plant Sci. 43, 21–24. Sørensen, P., 2004. Immobilization, remineralization and residual effects in subsequent crops of dairy cattle slurry nitrogen compared to mineral fertilizer nitrogen. Plant Soil 267, 285–296. Sørensen, P., Amato, M., 2002. Remineralization and residual effects of N after application of pig slurry to soil. Eur. J. Agron. 16, 81–95. Sørensen, P., Jensen, E.S., 1995a. Mineralization of carbon and nitrogen from fresh and anaerobically stored sheep manure in soils of different texture. Biol. Fertil. Soils 19, 29–35. Sørensen, P., Jensen, E.S., 1995b. Mineralization-immobilization and plant uptake of nitrogen as influenced by the spatial distribution of cattle slurry in soils of different texture. Plant Soil 173, 283–291. Sørensen, P., Jensen, E.S., 1996. The fate of fresh and stored 15N-labeled sheep urine and urea applied to a sandy and a sandy loam soil using different application strategies. Plant Soil 183, 213–220. Sørensen, P., Jensen, E.S., 1998. The use of 15N labelling to study the turnover and utilization of ruminant manure N. Biol. Fertil. Soils 28, 56–63. Sørensen, P., Thomsen, I.K., 2005. Production of nitrogen-15-labeled pig manure for nitrogen cycling studies. Soil Sci. Soc. Am. J. 69, 1639–1643. Sørensen, P., Thomsen, I.K., 2005b. Separation of pig slurry and plant utilization and loss of nitrogen-15-labeled slurry nitrogen. Soil Sci. Soc. Am. J. 69, 1644–1651.
ARTICLE IN PRESS 60
Phillip M. Chalk et al.
Sørensen, P., Jensen, E.S., Nielsen, N.E., 1994a. Labelling of animal manure nitrogen with 15 N. Plant Soil 162, 31–37. Sørensen, P., Jensen, E.S., Nielsen, N.E., 1994b. The fate of 15N-labeled organic nitrogen in sheep manure applied to soils of different texture under field conditions. Plant Soil 162, 39–47. Stevens, R.J., Gracey, H.I., Laughlin, R.J., Logan, H.J., 1986. The influence of two soil nitrogen levels on the utilization of 15N-labeled ammonium nitrate by ryegrass. J. Sci. Food Agric. 37, 454–460. Stevens, R.J., Laughlin, R.J., Logan, H.J., 1987. Interactions between cow slurry and 15Nlabeled calcium nitrate as fertilizers for ryegrass production. J. Sci. Food Agric. 41, 309–314. Sun, J., Bai, M., Shen, J., Griffith, D.W.T., Denmead, O.T., Hill, J., Lam, S.K., Mosier, A.R., Chen, D., 2016. Effects of lignite application on ammonia and nitrous oxide emissions from cattle pens. Sci. Total Environ. 565, 148–154. Taghizadeh-Toosi, A., Clough, T.J., Condron, L.M., Sherlock, R.R., Anderson, C.R., Craigie, R.A., 2011. Biochar incorporation into pasture soil suppresses in situ nitrous oxide emissions from ruminant urine patches. J. Environ. Qual. 40, 468–476. Taghizadeh-Toosi, A., Clough, T.J., Sherlock, R.R., Condron, L.M., 2012. A wood based low-temperature biochar captures NH3-N generated from ruminant urine-N, retaining its bioavailability. Plant Soil 353, 73–84. Tagoe, S.O., Horiuchi, T., Matsui, T., 2008. Effect of carbonized and dried chicken manures on the growth, yield, and N content of soybean. Plant Soil 306, 211–220. Thompson, R.B., Fillery, I.R.P., 1998. Fate of urea nitrogen in sheep urine applied to soil at different times of the year in the pasture-wheat rotation in South Western Australia. Crop Pasture Sci. 49, 495–510. Thomsen, I.K., 2000. C and N transformations in 15N cross-labeled solid ruminant manure during anaerobic and aerobic storage. Bioresour. Technol. 72, 267–274. Thomsen, I.K., 2001. Recovery of nitrogen from composted and anaerobically stored manure labeled with 15N. Eur. J. Agron. 15, 31–41. Thomsen, I.K., 2004. Nitrogen use efficiency of 15N-labeled poultry manure. Soil Sci. Soc. Am. J. 68, 538–544. Thomsen, I.K., 2005. Crop N utilization and leaching losses as affected by time and method of application of farmyard manure. Eur. J. Agron. 22, 1–9. Thomsen, I.K., Kjellerup, V., 1997. Yields and N uptake of barley and ryegrass from soils with added animal manure differing in straw and urine content. Eur. J. Agron. 7, 285–292. Thomsen, I.K., Kjellerup, V., Jensen, B., 1997. Crop uptake and leaching of 15N applied in ruminant slurry with selectively labeled feces and urine fractions. Plant Soil 197, 233–239. Thomsen, I.K., Schjønning, P., Christensen, B.T., 2003. Mineralization of 15N-labeled sheep manure in soils of different texture and water contents. Biol. Fertil. Soils 37, 295–301. Trehan, S.P., 1994. Immobilization of 15NH4 by cattle slurry decomposing in soil. Soil Biol. Biochem. 26, 743–745. Trehan, S.P., Wild, A., 1993. Effects of an organic manure on the transformations of ammomium nitrogen in planted and unplanted soil. Plant Soil 151, 287–294. Uchida, Y., Clough, T.J., Kelliher, F.M., Hunt, J.E., Sherlock, R.R., 2011. Effects of bovine urine, plants and temperature on N2O and CO2 emissions from a sub-tropical soil. Plant Soil 345, 171–186. Uenosono, S., Takahashi, S., Nagatomo, M., Yamamuro, S., 2002. Labeling of poultry manure with 15N. Soil Sci. Plant Nutr. 48, 9–13. Vallis, I., Gardner, C.J., 1984. Short-term nitrogen balance in urine-treated areas of pasture on a yellow earth in the subhumid tropics of Queensland. Anim. Prod. Sci. 24, 522–528.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
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Vallis, I., Peake, D.C.I., Jones, R.K., McCown, R.L., 1985. Fate of urea nitrogen from cattle urine in a pasture-crop sequence in a seasonally dry tropical environment. Crop Pasture Sci. 36, 809–817. Wachendorf, C., Joergensen, R.G., 2011. Mid-term tracing of 15N derived from urine and dung in soil microbial biomass. Biol. Fertil. Soils 47, 147–155. Wachendorf, C., Taube, F., Wachendorf, M., 2005. Nitrogen leaching from 15N labeled cow urine and dung applied to grassland on a sandy soil. Nutr. Cycl. Agroecosyst. 73, 89–100. Wachendorf, C., Lampe, C., Taube, F., Dittert, K., 2008. Nitrous oxide emissions and dynamics of soil nitrogen under 15N-labeled cow urine and dung patches on a sandy grassland soil. J. Plant Nutr. Soil Sci. 171, 171–180. Welten, B.G., Ledgard, S.F., Schipper, L.A., Judge, A.A., 2013. Effect of amending cattle urine with dicyandiamide on soil nitrogen dynamics and leaching of urinary-nitrogen. Agric. Ecosyst. Environ. 167, 12–22. Whitehead, D.C., Bristow, A.W., 1990. Transformations of nitrogen following the application of 15N-labeled cattle urine to an established grass sward. J. Appl. Ecol. 27, 667–678. Williams, P.H., Haynes, R.J., 1994. Comparison of initial wetting pattern, nutrient concentrations in soil solution and the fate of 15N-labeled urine in sheep and cattle urine patch areas of pasture soil. Plant Soil 162, 49–59. Williams, P.H., Haynes, R.J., 2000. Transformations and plant uptake of urine N and S in long and short-term pastures. Nutr. Cycl. Agroecosyst. 56, 109–116. Williams, B.L., Dawson, L.A., Grayston, S.J., Shand, C.A., 2003. Impact of defoliation on the distribution of 15N-labeled synthetic sheep urine between shoots and roots of Agrostis capillaris and soil N pools. Plant Soil 251, 269–278. Woods, R.R., Cameron, K.C., Edwards, G.R., Di, H.J., Clough, T.J., 2017. 15N recoveries from ruminant urine patches on three forage types. Plant Soil 417, 453–465. Wu, C.-L., Shen, Q.-R., Mao, J.-D., Xu, Y.-C., 2010. Fate of 15N after combined application of rabbit manure and inorganic N fertilizers in a rice–wheat rotation system. Biol. Fertil. Soils 46, 127–137.
Tracing the dynamics of animal excreta N in the soil-plantatmosphere continuum using 15 N enrichment Phillip M. Chalka,∗, Caio T. Ináciob, Deli Chena a
Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, VIC, Australia Embrapa Solos, Rio de Janeiro, Brazil Corresponding author: e-mail address: [email protected]
b ∗
Contents 1. Introduction 2. Production of 15N-enriched animal excreta 2.1 Feeding 15N-enriched plant materials or urea to domestic animals 2.2 Addition of 15N-enriched urea or ammonium to unlabeled animal urine 2.3 Addition of 15N-enriched ammonium, urea, urine or feces to unlabeled animal waste slurries 3. Uniformity of 15N-labeling of excreta 3.1 Within feces 3.2 Within urine 3.3 Between feces and urine 3.4 Within slurry 4. Recovery of 15N-labeled excreta in plants and soil 4.1 Feces 4.2 Urine 4.3 Slurry 5. Relative efficiencies of 15N-labeled excreta and 15N-labeled synthetic fertilizer 6. Interactions between synthetic fertilizer N and animal excreta N 6.1 15N-labeled fertilizer + unlabeled excreta 6.2 15N-labeled excreta + unlabeled fertilizer 7. Losses of N from excreta-amended soils 7.1 As ammonia and nitrous oxide emissions 7.2 As nitrate and ammonium in leachates 8. The residual value of excreta N in crop sequences 9. Partial 15N balance 10. Conclusions Acknowledgments References
Advances in Agronomy ISSN 0065-2113 https://doi.org/10.1016/bs.agron.2019.10.004
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2019 Elsevier Inc. All rights reserved.
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Abstract The increased demand for organic farm products, and the attendant restrictions on the use of synthetic N fertilizers in both traditional and organic agriculture, has focused attention on the efficacy of organic sources of N, including animal excreta. However, questions arise in regard to the agronomic and environmental benefits of excreta as alternative sources of N. These questions are best addressed through the experimental use of 15N-enriched excreta, which enable the labeled source to be unequivocally traced through the soil-plant-atmosphere continuum, which N difference or N equivalence techniques cannot achieve. In contrast to organic and inorganic N compounds that can be purchased commercially with a specified 15N label on the component N moieties, 15N-enriched excreta must be prepared by the investigator. The methods of production and the uniformity of labeling of the components of 15N-enriched excreta (feces, urine) and their admixture (slurry), the N use efficiencies of excreta in crop production, and comparisons and interactions of excreta with synthetic N sources are reviewed. Losses of N from excreta-amended soils to the environment and the residual N value of excreta in crop sequences are also examined. It was concluded that while similar agronomic and environmental issues surround the use of both synthetic fertilizers and excreta as sources of N for plant nutrition, the processes differ in intensity and duration both spatially and temporally.
1. Introduction Intensive crop production worldwide has become reliant on the use of industrially-manufactured or so-called “synthetic” N fertilizers to maintain yields. However, excessive application of fertilizer N can lead to environmental problems such as eutrophication of surface waters, nitrate contamination of groundwater and increased emissions of the greenhouse gas, nitrous oxide. The use of organic fertilizers (crop residues, animal excreta, composts) as alternative or supplementary sources of N is a strategy that could limit potential environmental damage. In addition, the large increase in the production, marketing and consumption of organic foods in recent years has been a major force in the increased demand for organic fertilizers, since the use of synthetic fertilizers is prohibited in organic agriculture. Therefore, there is increased awareness of the important role that organic fertilizers can play in agriculture, and renewed interest in estimating the ability of organic fertilizers to supply N for crop uptake, either as a sole or complementary source of N. Quantifying the availability of N in organic fertilizer sources has been the subject of extensive investigation over many years. In its simplest form, it involves measurement of the difference in N uptake by a crop in the presence and absence of the organic fertilizer (i.e., the N difference method),
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which allows calculation of “apparent” N recovery (e.g., Kirchmann, 1990; Nannen et al., 2011; Paul and Beauchamp, 1995). The assumption is that the crop will take up the same amount of indigenous soil N irrespective of the treatment. However, there is considerable evidence that this assumption is invalid. A more complex but little used experimental approach consists of determining the “synthetic” fertilizer N equivalence of an organic fertilizer source, which involves a comparison of the yield or N uptake by a crop at a given rate of organic fertilizer addition with the response curve of several rates of “synthetic” N fertilizer (e.g., Cusick et al., 2006a; Mun˜oz et al., 2004). However, the non-isotopic methods suffer from greater variability (Cusick et al., 2006a; Mun˜oz et al., 2004). Organic fertilizers such as animal excreta and composts are naturally enriched in the stable isotope 15N, and this can be used as a qualitative tracer to follow the dynamics of N in conventional and organic farming systems (Chalk et al., 2014, 2019; Ina´cio et al., 2015; Ina´cio and Chalk, 2017). Alternatively, it is possible to artificially enrich organic fertilizers with 15 N and use this as a quantitative or semi-quantitative tracer to differentiate the labeled organic N source from the unlabeled indigenous soil N. For example, it is a simple matter to produce 15N-enriched plant material by applying 15N-enriched fertilizer, and numerous studies have been conducted on the recovery of 15N-labeled crop residues by subsequent crops. 15Nlabeled crop residues or grain can be fed to animals to produce 15N-labeled excreta, which can be taken one step further to produce 15N-enriched compost (Chalk et al., 2013). Twenty-one years ago, Dittert et al. (1998) published a review on 15Nbased studies of N turnover in soil following application of animal feces and slurry. The objective of the present review is to complement and extend the earlier review with an analysis of the more recent and extensive literature, while also providing a somewhat different emphasis and perspective. The review will cover 15N-labeling strategies of both fecal and urinary N, the uniformity of 15N-labeling within and between the components of excreta, transformations and crop recovery of excreta N added to soil, leaching and gaseous N losses, interactions of excreta N with synthetic fertilizer N, and the residual value of excreta N in soil.
2. Production of 15N-enriched animal excreta Animal excreta is composed of feces (solid or semi-solid) and urine (liquid). Feces and dung are interchangeable terms. On the other hand, manure can have a dual meaning, either the solid fraction or an admixture
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of dung and urine, the latter being commonly known as slurry. In order to circumvent possible confusion, we will refer to the constituents of excreta as feces, urine and slurry, and will avoid the use of the term “manure” except where “farmyard manure” or “green manure” are in common usage. Several methods have been used to introduce an enriched 15N label into animal excreta, which is composed of both organic and inorganic N constituents within feces and urine components. The methods are summarized in Table 1. The natural approach is to feed animals with 15N-enriched forage or grain and then collect and preserve the excreta produced. The artificial approach is to collect urine or slurry from animals, or synthesize artificial urine, and enrich it with 15N by addition of 15 NH4 + or 15N-enriched urea.
2.1 Feeding animals
15
N-enriched plant materials or urea to domestic
A range of 15N-labeled forages (grass, silage, hay) have been fed to sheep and goats (Table 2) and cattle (Table 3) while grains (barley, peas, soybean, rice, maize) have been fed to poultry (Table 4) and pigs (Table 5) to obtain 15 N-labeled excreta. In one case labeled ryegrass was fed to rabbits (Wu et al., 2010). 15N-labeled forage can be produced by addition of the isotope to the soil or hydroponic solution culture, or by foliar application of urea with a surfactant and urease inhibitor (e.g., Ingold et al., 2018). A non-lactating animal is often used so that isotope will not be excreted in milk (e.g., Garza et al., 2009; Hoekstra et al., 2011; Mun˜oz et al., 2004; Powell et al., 2004, 2005), although the feces composition may be slightly different compared to a lactating cow (Powell et al., 2004). A period of 1–3 weeks of pre-feeding the equivalent unlabeled forage was usually adopted before the changeover to the labeled diet (Tables 2–5), or fasting was employed prior to the feeding of labeled material (e.g., Primo et al., 2014). The period of labeled feeding was quite variable lasting from 36 h to several weeks (Tables 2–5), depending on the amount of material available and the test animal. Excreta collection generally continued for a period of several days following cessation of the labeled diet. In addition to feeding 15N-labeled plant material (the forage method), Powell et al. (2004) fed 15N-enriched urea to cows with unlabeled forage (the urea method) (Table 1). The authors claim that this method only produced labeled urine and fecal endogenous N, with undigested feed N remaining unlabeled. A variation of this technique was adopted by Powell et al. (2005), in which urea was administered periodically through a rumen fistula.
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Table 1 Natural and artificial strategies to enrich animal excreta with 15N. Labeling strategy Animal Reference
Feces and urine Fed 15N-enriched forage, silage or grain
Various
See Tables 2–5
Fed 15N-enriched urea with Cow unlabeled forage
Powell et al. (2004) and Hoekstra et al. (2011)
Add 15N-enriched urea to rumen through fistula
Cow
Powell et al. (2005)
Cow
Lee et al. (2014)
Add 15N-enriched urea or 15 NH4 + to unlabeled urine
Various
See Tables 10, 11, and 17
Add 15N-enriched urea + 15 N-glycine to unlabeled urine
Synthetic, Fraser et al. (1994), Di et al. (2002), and cow Silva et al. (2000, 2005)
Add 15 NO3 to unlabeled urine
Cow
Add pulses of rumen
15
NH4 + to
Urine
Monaghan and Barraclough (1993)
Slurry Add 15N-enriched urea or Various 15 NH4 + to unlabeled slurry
See Tables 12, 13, and 18
Mix 15N-enriched feces with 15N-enriched urine
Various
Chadwick et al. (2001), Mun˜oz et al. (2003, 2004), Cusick et al. (2006a,b), and Powell et al. (2004, 2005)
Mix 15N-enriched urine with unlabeled feces
Sheep
Bosshard et al. (2008, 2009)
Cattle
Hoekstra et al. (2011)
Mix 15N-enriched feces with unlabeled urine Add 15N-enriched urine to unlabeled slurry Add 15N-enriched feces to unlabeled slurry
Table 2
15
N enrichment of feed sources and excreta of sheep and goats. Time (d)
15
Reference
N-labeled Animal feed source
Adapta Feedb Collectb
He et al. (1992, 1994)
Goat
Rice straw
6–7
Catchpoole and Blair (1990)
Goat
Gliricidia, Leucaena 35
Sørensen et al. (1994a)
Sheep Ryegrass hay
Sørensen and Jensen (1996)
Sheep Ryegrass hay
Thomsen et al. (1997)
Sheep Ryegrass
31
38
Jensen et al. (1999)
Sheep Ryegrass hay
31
38
7
2–3
15
N (atom% excess)
Feed
14–17
Fecesc Urinec Peak
15
Nc (d)
5.92
2.5 (F, U)
3.70
10 (F)
1.5 (U) 3.0 (F) 9
17
4.52
35
35
4.73
2.91 2.85
5.19
4.04
3.25
3.96
2.65
2.03
31–37
2.93
2.77
38–44
3.06
2.94
2.88
2.58
19–22 (F)
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4.04
29–30 (U) Thomsen (2000)
Sheep Ryegrass
22
22
24–30
Thomsen (2001)
Sheep Ryegrass
22
22
Bosshard et al. (2008, 2009)
Sheep Ryegrass hay
7
9
9
Bosshard et al. (2011)
Sheep Ryegrass hay
7
9
11
14.23 10.96 8.54
Primo et al. (2014)
Goat
2d
2–3
2–3
4.81
Martı´nez-Alca´ntara et al. (2016b) Sheep Forage maize
7
18
Daily
Ingold et al. (2018)
7
a
Fed unlabeled material. Fed 15N-labeled material. F, feces; U, urine; S, slurry. d Fasting. b c
Goat
Brachiaria
Rhodes grass hay
3.96
3.30–5.61 (S)
1.99 2.28
0.31
16 (F, U)
0.16
12–19 (F)
Table 3
15
N enrichment of feed sources and excreta of cattle. Time (d)
15
N-labeled feed source
Reference
Powell and Wu (1999), Mun˜oz et al. (2003, 2004), Hay + silage and Cusick et al. (2006a,b) Barkle et al. (2001)
Fecesc Urinec Peak
7
1.97
1.5
8
3.66
1.27
3 21
Ryegrass hay
8
8
2.63
0.96
0.56
17
Daily
2.11
1.67
1.22
Garza et al. (2009)
Sudangrass
10
10
7
0.36
Hoekstra et al. (2011)
Pasture
7
3
5
2.63–9.63
Nannen et al. (2011)
Maize silage
Wachendorf and Joergensen (2011)
Ryegrass hay
17
Daily
2.48
2.00
1.58
Barros et al. (2017)
Alfalfa silage
4
4
0.26
0.25
0.16
Corn silage
0.21
0.20
0.12
Corn grain
0.19
0.14
0.10
Soybean meal
0.25
0.17
0.15
Fed unlabeled material. Fed 15N-labeled material. F, feces; U, urine; S, slurry. d Dung collected days 10–17 bulked; urine collected days 7–17 bulked. c
2.5 (F)
2.58
Hay + silage
b
Nc (d)
1.5 (U)
Lampe et al. (2006)
a
15
3 (F, U)
0.35 (S) 0.16
0.36 (S)
2–4 (F, U)
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Wachendorf et al. (2005, 2008)
Hay d
N (atom% excess)
Adapta Feedb Collectb Feed
Pasture
Langmeier et al. (2002)
15
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Phillip M. Chalk et al.
15
N enrichment of feed sources and feces of poultry. 15
Time (d)
15
Reference
Kirchmann (1990)
N-labeled feed source Adapta Feedb Collectb Feed
Barley grain
Abdelhamid et al. (2004)
Rice grain
Thomsen (2004)
Barley + peas
Liu et al. (2008) Cabbage Tagoe et al. (2008)
Rice grain
Holbeck et al. (2013)
Maize straw
Feces
Peak N (d)
15
1.543 1.034
Bergstr€ om and Barley grain Kirchmann (1999) Uenosono et al. Rice grain (2002)
N (atom% excess)
14
21
29
1.54
1.16
2.57
1.69
22
0.47 5
5.39c 4.25c
15 15
12.24
7
4.22 0.81–0.85
7
14
8.17
1.97
a
Fed unlabeled material. Fed 15N-labeled material. 35 g peas (4% N, 7.41 atom% 15N excess) + 85 g barley (1.82% N, 3.57 atom% 15N excess); , estimated from figure. b c
Powell et al. (2004, 2005) suggested that the forage method with a potentially high 15N enrichment was more suited to long-term studies, whereas the urea method with generally lower 15N enrichment was suitable for short-term studies. Several authors have commented on the difficulty of sampling feces and urine individually without cross contamination, and have therefore bulked the excreta to make slurry (e.g., Bosshard et al., 2008, 2009; Chantigny et al., 2004a,b; Jayasundara et al., 2010; Lampe et al., 2006; Nannen et al., 2011). In order to avoid the mixing of feces and urine, indwelling bladder catheters were fitted to pigs (Sørensen and Thomsen, 2005) and cows (Powell et al., 2004, 2017; Powell and Wu, 1999). Excreta were commonly preserved by freezing or the addition of acid to prevent NH3 volatilization.
Table 5
15
N enrichment of feed sources and excreta of pigs.
Reference
15
He et al. (1994)
Green manure
6–7
2–3
Chantigny et al. (2004a,b)
Soy + barley
7
Sørensen and Thomsen (2005)
Barley + peas
5
Jayasundara et al. (2010)
Corn + soybean
Cavalli et al. (2018)
Corn
a
Fed unlabeled material. Fed 15N-labeled material. F, feces; U, urine; S, slurry.
b c
N-labeled feed source
Adapt
7
a
Fecesc
Urinec
14–17
9.73
5.46
5.24
12
20
2.44
11
11
2.37
2.19
4
6
0.61–1.36
0.58–1.00 (S)
3–
6.08
Collect
b
N (atom% excess)
Feed
Feed
b
1.96 (S) 1.71
2.74 (S)
Peak
15
Nc (d)
8 (S) 11 (F, U)
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Time (d)
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2.1.1 Temporal change in excreta 15N abundance After the start of feeding of pigs with a mixture of 15N-enriched peas and barley grains, the 15N abundance of urine N quickly increased while that of feces was initially slower (Sørensen and Thomsen, 2005; Fig. 1A). However, after 3 d the 15N abundance of fecal N exceeded that of urinary N. A similar pattern was observed for sheep by Bosshard et al. (2011) (Fig. 1B) and Sørensen and Jensen (1998) (Fig. 1C) that were fed ryegrass hay, while the same phenomenon was observed for cows fed alfalfa silage (Barros et al., 2017; Fig. 1D). At the end of the 11-d feeding period, the 15N abundance of fecal N was 7% lower than in the feed (Sørensen and Thomsen, 2005; Fig. 1A), which
Fig. 1 Time course of 15N abundance of feces and urine of (A) pigs fed with a mixture of 15 N-enriched peas and barley grains, (B) and (C) sheep fed with 15N-enriched ryegrass hay, and (d) lactating cows fed with 15N-enriched alfalfa silage. Arrow in (D) denotes cessation of labeled feeding. Reproduced with permission from Panel (A): Sørensen, P., Thomsen, I.K., 2005. Production of nitrogen-15-labeled pig manure for nitrogen cycling studies. Soil Sci. Soc. Am. J. 69, 1639–1643; Panel (B): Bosshard, C., Oberson, A., Leinweber, P., Jandl, G., Knicker, H., Wettstein, H.-R., Kreuzer, M., Frossard, E., 2011. Characterization of fecal nitrogen forms produced by a sheep fed with 15N labeled ryegrass. Nutr. Cycl. Agroecosyst. 90, 355–368; Panel (C): Sørensen, P., Jensen, E.S., 1998. The use of 15N labelling to study the turnover and utilization of ruminant manure N. Biol. Fertil. Soils 28, 56–63; and Panel (D): Barros, T., Powell, J.M., Danes, M.A.C., Aguerre, M.J., Wattiaux, M.A., 2017. Relative partitioning of N from alfalfa silage, corn silage, corn grain and soybean meal into milk, urine, and feces, using stable 15N isotope. Anim. Feed Sci. Technol. 229, 91–96.
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was attributed to excreted unlabeled endogenous N (Sørensen et al., 1994a), while the 15N abundance of urinary N was 28% lower than in the feed. Milk had a slightly lower 15N abundance than urine but followed the same trend (Barros et al., 2017; Fig. 1D), clearly illustrating the economy of using a non-lactating cow for production of labeled excreta. In order to obtain uniformly labeled feces or urine, the daily collections of each excreta type were combined once a stable plateau in 15N abundance was reached (Fig. 1). For example, Wachendorf et al. (2008) bulked urine collected between days 10 and 17 while feces collected between days 7 and 17 were combined when a cow was fed with 15N-enriched grass silage. 2.1.2 Recovery of labeled dietary N in the excreta The fraction of labeled dietary N recovered in the excreta is given by Eq. (1): Labeled dietary N recovery ¼ Ndiet 15 N enrichmentdiet = Nexcreta 15 N enrichmentexcreta
(1)
where 15N enrichment is expressed as atom% 15N excess. 15N enrichment is determined by subtracting the 15N abundance (atom% 15N) of the equivalent unlabeled diet and excreta from the labeled diet and excreta, respectively. The fractional recovery can be expressed as a percentage by multiplying by 100. Few quantitative data exist on the recovery of labeled dietary N in excreta (Table 6). When 15N-labeled rice straw was fed to goats for 2–3 days, 28 and 6% of dietary 15N excess was recovered in feces and urine, respectively (He et al., 1992). A considerably higher percentage of excess 15N in green manure fed for 2–3 days to pigs was recovered in urine (29%), while an approximately equal amount (24%) was recovered in feces (He et al., 1994). Similar amounts of feed-derived excess 15N were also recovered in feces (29%) and urine (31%) of cows fed labeled alfalfa hay and corn silage for 36 h (Powell and Wu, 1999). On the other hand, Uenosono et al. (2002) estimated that 41% of 15N-labeled rice grain fed for 21 days to poultry was voided in feces. In a study involving lactating dairy cows, Barros et al. (2017) found consistent recoveries of four 15N-labeled forages (alfalfa silage, corn silage, corn grain, soybean meal) within feces (26–27%) and within urine (37–39%). Recovery in milk was similar to feces (22–25%). The loss of 50–65% of dietary N in excreta indicates a low efficiency of conversion to meat and milk.
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Table 6 Recovery of 15N-labeled plant materials fed to domestic animals. 15 15 15
N (atom% excess)
N recovery (%)
Reference
N-labeled Animal feed source Feed Feces Urine Feces Urine
He et al. (1992, 1994)
Goat
Rice straw
He et al. (1994)
Pig
Green manurea
9.73 5.46
Hay + silagec
3.66 1.97
Powell and Wu (1999)b Cow
Uenosono et al. (2002) Poultry Rice grain Barros et al. (2017)
Cow
d
5.92
28
6
5.24
24
29
1.27
29
31
2.57 1.69
Alfalfa silage 0.26
Fig. 1D
41 26
39
Corn silage 0.21
27
38
Corn grain
0.19
27
37
Soybean meal
0.25
26
38
a
Milk vetch + cowpea + rape. The same feeding procedure was used by Mun˜oz et al. (2003, 2004) and Cusick et al. (2006a,b). Alfalfa hay + corn silage. d Lactating. b c
On the other hand, this low efficiency is a boon for studies of 15N-enriched excreta, giving a more uniform labeling than can be achieved by adding labeled urea or ammonium to urine or slurry (Section 3).
2.2 Addition of 15N-enriched urea or ammonium to unlabeled animal urine More than 60% of N excreted from cattle and sheep is in urine (Haynes and Williams, 1993). The concentrations of N containing constituents of urine from dairy cattle were reviewed by Dijkstra et al. (2013). Many studies have been conducted with animal urine which has been artificially-labeled with 15 N (Table 1). Since 60–80% of the N in urine occurs as urea (Dijkstra et al., 2013; Kirchmann, 1991; Sørensen and Jensen, 1996) it is logical to label urine by addition of a small quantity of urea highly labeled in 15N (99 atom%), which has been adopted in the majority of studies (Table 1). However, in a minority of studies 15 NH4 + has been added rather than urea, since urea will be rapidly hydrolyzed to NH4 + on contact with soil, while in other studies 15N-labeled glycine has been added together with the 15N-urea
ARTICLE IN PRESS 13
Tracing the dynamics of animal excreta N
Table 7 Synthetic urine formulations.
Reference
Urea
Constituent (g L21) Hippuric K2SO4 KBr Glycine acid Total N
KHCO3 KCl
de Klein and van 28.50 22.90 16.9 – Logtestijn (1994), Ambus et al. (2007), and Carter (2007)a
–
Fraser et al. (1994), 23.75 22.15 Clough et al. (2003), and Clough and Kelliher (2005)
3.95 6.70
6.35 6.15
Clough et al. (1996, 1998)
4.20 2.30
6.70 4.84
23.30
Shand et al. (2000) and Williams et al. (2003)
42.8 46.2
–
7.6 3.8
21.4
Clough et al. (2004) 17.40 23.33
8.35 2.29
4.84
Welten et al. (2013) 13.6 13.9
5.0 1.5
3.4
Ayadi et al. (2015) a
22.6 23.1
11.9
15.6
10.0
9.0
b
3.8 1.9
1
Minor constituents (g L ) not shown; uric acid, 0.2; NH4Cl, 1.4; allantoin, 0.6; creatinine, 0.3. Authors state it was potassium chlorate (KClO3).
b
in the ratio of 1:9, in order to label part of the organic N fraction of urine (e.g., Carey et al., 2017, 2018; Di et al., 2002; Fraser et al., 1994). In addition to the use of animal urine, several authors have used synthetic urine (Table 7) presumably to avoid the inconvenience and complication of collecting animal urine uncontaminated by feces.
2.3 Addition of 15N-enriched ammonium, urea, urine or feces to unlabeled animal waste slurries Slurry is normally defined as a mixture of fecal and urinary N in suspension. However, a slurry can also consist of a mixture of feces and water without urine (e.g., Martı´nez-Alca´ntara et al., 2016b; Sørensen and Jensen, 1995a, 1998). Many studies have been conducted with slurries of feces + urine which have most often been artificially-labeled with 15N by addition of 15 N-enriched ammonium salts or urea (Table 1). Feces contains 2–3% organic N, no nitrate and little ammonium (Thomsen et al., 2003), while
ARTICLE IN PRESS 14
Phillip M. Chalk et al.
total N in fresh poultry excreta consists of 61% uric acid N (Kirchmann, 1991). Hydrolysis of urea or uric acid to ammonium is rapid, and after several hours or days, 50–60% of slurry N is present as ammonium-N, which forms the rationale for addition of 15N-enriched ammonium to artificially label the slurry. Several variations for obtaining 15N-labeled slurry have been employed (Table 1). For example, Hoekstra et al. (2011) labeled slurry by adding labeled urine or feces to unlabeled slurry. The treatments were (i) 15Nlabeled urine obtained by feeding labeled herbage was added to unlabeled slurry; (ii) 15N-labeled feces obtained by feeding 15N urea with unlabeled herbage was added to unlabeled slurry; (iii) 15N-labeled feces obtained by feeding labeled herbage was added to unlabeled slurry.
3. Uniformity of 15N-labeling of excreta Feces are mainly composed of organic N compounds synthesized during passage of plant material through the animal gut as well as residual (undigested) organic N. Urine is a mixture of various organic N compounds and inorganic N derived from the hydrolysis of its principal constituent, urea. The importance of uniform 15N-labeling of the components of excreta has been expressed by several authors (e.g., Chantigny et al., 2004b; Sørensen and Jensen, 1998). A heterogeneous distribution of 15N between the rapidly and the slowly mineralizable N pools of animal excreta will distort estimates of the actual rates of N mineralization and hence crop recovery (Sørensen et al., 1994a), which are then a function of both elapsed time and the relative contribution of the various N pools to mineral 15N (Chantigny et al., 2004b). Therefore it is important to ascertain the extent to which there is isotopic uniformity within the components of animal excreta (feces and urine) if used individually as well as within these components if they are combined in slurry. It is also important to determine if feeding and sampling strategies can be devised to minimize non-uniformity, and also to estimate the likely errors in plant recovery of 15N-labeled excreta due to a non-uniform distribution of 15N.
3.1 Within feces The uniformity of 15N-labeling of feces has been tested by total and extractable N analyses (Bosshard et al., 2011; Langmeier et al., 2002; Sørensen et al., 1994a) or through sequential acid hydrolysis techniques (Kirchmann, 1990; Uenosono et al., 2002) (Table 8). Inconsistent differences were found
ARTICLE IN PRESS 15
Tracing the dynamics of animal excreta N
Table 8 Distribution of 15N in bulk material or N fractions of labeled feces. 15 N (atom% g N kg21 Recovery excess)a DM (%) Reference Animal N fraction
Kirchmann (1990)
Poultry Total N
Sørensen Sheep et al. (1994a)
Bosshard Sheep et al. (2011)
1.034
0.27 M H2SO4
1.021
1.75 M H2SO4
1.014
12.5 M H2SO4
1.049
Total N
30.8
NH4 +
0.36
1.2
2.96
H2O soluble
7.0
25.0
3.83
91.2 0.3
1.65 0.03 bc
7.7 0.1
1.67 0.01 bc
Amide
5.5 0.3
2.67 0.49 a
Hexosamine
21.9 1.8
1.44 0.03 bc
α-Amino
28.4 1.0
1.82 0.06 b
Unidentified
28.5 3.1
1.44 0.10 bc
Non-hydrolysable
7.3 0.5
1.23 0.06 c
Total N
100.0
0.962 0.001 b
Undigested
10.7 0.44 0.648 0.028 a
Debris
76.9 1.24 0.997 0.011 b
H2O soluble
12.5 1.43 1.014 0.040 b
Total N
100.0
10.93 0.03 ab
Undigested
33.0
10.33 0.05 b
Debris
53.1
11.63 0.16 a
H2O soluble
13.6
9.48 0.50 c
Uenosono Poultry Hydrolysable et al. (2002) NH4 +
Langmeier Cow et al. (2002)
14.6
3.70
a Different lowercase letters within individual studies denote significant differences (P < 0.05) in enrichment between N fractions.
15
N
among total and identifiable extractable N fractions of sheep (Bosshard et al., 2011; Sørensen et al., 1994a) and cow (Langmeier et al., 2002) feces (Table 8). However, a reasonably uniform 15N distribution in poultry excreta was indicated by similar 15N signatures in the bulk material and N fractions sequentially extracted with H2SO4 (Kirchmann, 1990). Uenosono et al. (2002)
ARTICLE IN PRESS 16
Phillip M. Chalk et al.
similarly found non-significant differences in the 15N signatures of the bulk material, total hydrolysable N, NH4 + , hexosamine N, α-amino N and unidentified N (1.44–1.82 atom% excess) in poultry excreta. However, amide N was significantly higher and non-hydrolysable N was significantly lower in 15N enrichment compared with the other fractions, but they represented only small percentages of the total (5.5% and 7.3%, respectively). The uniformity of the 15N enrichment of sheep feces has also been appraised by an incubation technique proposed by Sørensen et al. (1994a). Moist and homogenized labeled feces (10 mg N) was mixed with dry quartz sand (50 g), adjusted to 55% of the water holding capacity and incubated in bottles covered with Al foil at 20 °C. Water loss was replenished weekly and samples were extracted at various times with 2 M KCl for determination and isotope-ratio analysis of inorganic N (NH4 + + NO3 ). Using the 15N enrichment of the mineralizable N of sheep feces (as determined by Sørensen et al., 1994a) rather than that of the sheep total fecal N, Sørensen et al. (1994b) demonstrated that the 15N recovery by a barley crop in three soils increased by only 3% (from 14% to 17%). Based on the sand incubation technique, Sørensen and Jensen (1998) concluded that it is possible to produce nearly uniformly labeled ruminant feces. On the same basis, Sørensen and Thomsen (2005) found that labeled pig feces had a relatively homogeneous 15N enrichment, even though the diet of labeled pea and barley grain differed in 15N enrichment.
3.2 Within urine The labeling of urine N derived from the feeding of a 15N-enriched diet can be regarded as homogeneous ( Jensen et al., 1999; Sørensen and Jensen, 1996). For example, Sørensen and Jensen (1996) found that the ammoniacal-N and total N in urine had similar 15N abundances (3.22 and 3.28 atom% 15N, respectively) after feeding labeled ryegrass to sheep for 1 month. Alternatively, several authors have prepared 15N-labeled artificial urine by adding both labeled urea and labeled glycine in the ratio of 9:1 (Di et al., 2002; Fraser et al., 1994; McLaren et al., 1993; Silva et al., 2000, 2005). While uniform labeling can be achieved between these two components of urine, the other organic nitrogenous constituents of artificial urine (Table 7) do not isotopically exchange with urea and glycine and are therefore not uniformly labeled. Therefore, the feeding of 15N-enriched plant materials to animals appears to be the optimum strategy to achieve uniformly labeled urine, although as noted previously, it is difficult to obtain urine uncontaminated by feces.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
17
3.3 Between feces and urine When fed an 15N-enriched diet, feces N was consistently more enriched than urine N, irrespective of the animal species (Tables 2, 3, and 5; Fig. 1). Chalk et al. (2014) also observed the same relative difference in their review of 15N natural abundance of animal feces and urine. According to Sørensen and Thomsen (2005), the difference in 15N enrichment of feces and urine makes it difficult to label total slurry N uniformly. As a consequence, these authors recommend that the dynamics of urine and feces N should be followed separately as the lability of N in these components is different ( Jensen et al., 1999). For example, Chantigny et al. (2004b) found that the 15N enrichment of the N mineralized from an admixture of feces and urine was less than the 15N enrichment of the total N pool. Therefore Sørensen and Thomsen (2005) recommend that the labeled component be mixed with the other excreta components in unlabeled form as practiced by several authors (e.g., Jensen et al., 1999; Thomsen et al., 1997). This allows the fate of each component to be estimated separately, while the fate of the total excreta N can be calculated from the weighted recovery of N from each component. As an alternative, Sørensen and Thomsen (2005) suggested that feces and urine having similar 15N enrichments can be mixed.
3.4 Within slurry As noted previously, slurry is not uniformly labeled with 15N whether produced naturally by feeding 15N-enriched forage or grains, or whether it is artificially produced through addition of 15N-enriched urea or ammonium salts. In the latter case, the added isotope will only equilibrate with the mineral N fraction of the slurry, and will not mix initially with the large organic N component of the slurry. In recognition of the non-uniform distribution of 15N within slurry, several authors have expressed the 15N abundance of slurry on the basis of the NH4 + fraction, rather than the total N content (e.g., Dittert et al., 2001; Dosch and Gutser, 1996; Paul and Beauchamp, 1995; Sørensen and Jensen, 1995b; Trehan, 1994). For example, the 15N abundance of the total slurry N and the ammonium-N in the slurry were 0.98 and 1.25 atom% 15N, respectively (Chadwick et al., 1998) and 1.45 and 4.29 atom% 15N, respectively (Dittert et al., 2001). Therefore, the recovery of labeled slurry N by plants is a measure of the availability of the NH4 + fraction of the slurry and not the total slurry N per se, thus compromising comparisons of recovery with uniformly labeled feces, urine or synthetic fertilizer. The recoveries of slurries enriched in 15N by addition of labeled inorganic N or urea, can therefore only be regarded as semi-quantitative.
ARTICLE IN PRESS 18
Phillip M. Chalk et al.
4. Recovery of
15
N-labeled excreta in plants and soil
The proportion of N in the plant derived from the labeled excreta (Ndfeplant) is given by Eq. (2), based on the assumption that the excreta is uniformly labeled. Ndfeplant ¼ 15 N enrichmentplant =15 N enrichmentexcreta
(2)
where 15N enrichmentplant ¼ 15N abundanceplant – 15N natural abundanceplant. 15 N natural abundanceplant is determined by analysis of the plant growing in the same soil under the same conditions without added excreta. The unit of 15N abundance is atom% 15N, while the unit of 15N enrichment is atom% 15 N excess. Eq. (2) is used to calculate the proportion of N in the soil derived from the labeled excreta by replacing “plant” with “soil.” The recovery of labeled excreta N in the plant (Rplant) is given by Eq. (3) Rplant ¼ Ndfeplant Nplant =ðNdfeexcreta Nexcreta Þ (3) where N is the total N content [N concentration (mg g1) dry matter (g)]. Eq. (2) is used to calculate the recovery of labeled excreta N in the soil by replacing “plant” with “soil.” Recoveries are expected to be season- and species-specific (annual vs perennial). Other variables affecting recoveries in plants and soil include the form of excreta (feces, urine, slurry), method of application (e.g., surface, banding, injection, etc.), soil and excreta pH, soil total N and excreta N rate, method of 15N-labeling and experimental scale (laboratory, pot, lysimeter and field) and duration.
4.1 Feces Relatively few studies have been conducted on the recoveries of labeled feces in plants and soil (Table 9) compared with those with urines (Section 4.2) and slurries (Section 4.3). Laboratory, pot, lysimeter and field studies were conducted using surface soils of acidic and alkaline pH, and with variable total N contents (Table 9). Feces derived from several domestic animals were obtained by feeding an 15N-enriched diet of forages or grains. Rates of feces additions were quite variable, ranging from 92 to 8000 mg kg1 soil in laboratory and pot studies, and from 87 to 1052 kg ha1 in lysimeter and field studies. Feces was mixed with the soil (Nishida et al., 2004; Primo et al., 2014; Sørensen et al., 1994b; Wu et al., 2010), banded (Thomsen et al., 2003) or
Table 9 Recovery of 15N-labeled feces in crops and soil in laboratory, pot, lysimeter and field experiments. Soil Feces added Reference
15
N recovery (%)
15
Rate Total pH N (g kg21) Animal (kg ha21)a
N (atom%) Crop and duration
6.4 1.3
Sheep (92)
4.18
7.0 1.5
(94)
7.4 1.5
(104)
Crop Soil
Total
Laboratory studies
Cusick et al. (2006b)
7.6 0.3
Cow
14.7
5.0 0.9
Rabbit (150)
Not applicable. Soil was incubated for 28 d
NA, 168 d
89–102
26
26
Pot studies Wu et al. (2010)
19.4
7.3 1.3 Primo et al. (2014)
Martı´nez-Alca´ntara et al. (2016a)
6.7 0.5
8.4
Goat
(8000)
Sheep 20 g tree
2.35
1
2.54
Rice-wheat rotation, harvested at maturity
8, 8
Maize, 50 d
7
Cotton, 50 d
7
Cowpea, 50 d
8
Mandarin, 10 months
30
69, 40 77, 48
16, 5 68, 39 84, 44
32b
62 Continued
ARTICLE IN PRESS
Thomsen et al. (2003)
Table 9 Recovery of 15N-labeled feces in crops and soil in laboratory, pot, lysimeter and field experiments.—Cont’d Soil Feces added
15
N recovery (%)
15
N (atom%) Crop and duration
Crop Soil
Total
Sørensen et al. (1994b)
8.0 1.8
Sheep 87
3.93
Barley + ryegrass, 18 months
24
100
Wachendorf et al. (2005)
5.9 2.7
Cow
1052
2.04
Pasture, 2 y
Pig
459
Cow
1052
Lysimeter studies 76
75c
Field studies Nishida et al. (2004) Wachendorf and Joergensen (2011) 5.1 Data in parentheses are mg kg1. Includes 2% as NH4 + + NO3 . c 2-year average. d In microbial biomass, 2-year average. a
b
2.2
Rice, 113 d 2.00
Pasture, 189 d
25
57 16d
82
ARTICLE IN PRESS
Rate Total pH N (g kg21) Animal (kg ha21)a
Reference
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
21
applied to the soil surface (Martı´nez-Alca´ntara et al., 2016b; Wachendorf et al., 2005; Wachendorf and Joergensen, 2011). Cereal, pasture and fruit crops were grown and harvested over periods ranging from 50 days to 2 years. Given the contrasting experimental conditions, it is not surprising that plant recoveries were quite variable, ranging from as little as 7% to as much as 30%, while soil recoveries were generally higher, ranging from 16% to 76% (Table 9). On two occasions, quantitative recoveries of labeled feces in plants and soil were obtained, while total recoveries often exceeded 75% for cereals as a first rotation crop (Table 9).
4.2 Urine Laboratory, pot and lysimeter studies conducted with 15N-labeled urine are summarized in Table 10. All but one of the soils were acidic while total N ranged from a low of 0.7 to a high of 18.5 g kg1 soil. However, other than this single maximum value all were <8.8 g kg1 soil. Synthetic or natural urine from a range of animals was applied to the soil surface at rates ranging from 26 to 100 g N m2. Grasses grown alone or in mixed swards with legumes were cut at various intervals, from a single cut at day 28 to multiple cuts finishing at year 2 (Table 10). Recoveries of urine N in plant material were very variable, ranging from as little as <1% to as much as 58%, while soil recoveries were generally <30% (excluding laboratory studies). In a few cases measurable quantities of NH4 + + NO3 were present. The highest total recovery was 86%, but several values were below 50%. Field studies conducted with 15N-labeled urine are summarized in Table 11. All but one of the soils were acidic with total N ranging from 0.8 to 3.8 g kg1 soil. Natural urine derived from either sheep or cattle was applied at rates ranging from 6 to 105 g N m2. With only one exception (370-day wheat), either pasture or pasture grasses were grown and cut at various intervals, starting with a single cut at day 14 and finishing with multiple cuts at day 350. Plant and soil recoveries ranged from 1% to 65%, and from 13% to 66%, respectively. Total recoveries were within the range of 37–88%. The lack of quantitative recoveries in plants and soil indicates the potential for losses of urine N via leaching and gaseous N emissions (Section 7). In addition, the recovery data will depend on how the urine was labeled, and on how the 15N enrichment of the urine was expressed, i.e., as total urine N or as the inorganic N fraction of the urine with which added 15N equilibrated.
Table 10 Recovery of 15N-labeled animal urine in crops and soil in laboratory, pot and lysimeter experiments. 15 Soil Urine N addeda N recovery (%) Reference
pH
Cropa and N (atom%) duration
Total N (g kg21) Typeb g m22
15
0.7
2.0
Soil
NH4+ + NO32 Total
NA, 28 d
30
32
NA, 42 d
75
12
Crop
Laboratory studies Bronson et al. (1999) 5.0
Synt
50
7.7 Cusick et al. (2006b) 7.6
62
5.3 0.3
Cow 14.7
NA, 168 d
63
63
Pot studies Williams et al. (2003) Ambus et al. (2007)
5.6
Uchida et al. (2011) 5.6
6.6
Synt
50
2.0
G, 56 d
0.8c
28
15
Synt
26–51 5.2
P, 42 d
18–20
10–20
8–20
48
Cow 59
0.996
R, 28 d
1.6–7.0
McLaren et al. (1993)
Synt
50
5.0
P, 1 y
40, 44d
26, 20d
66, 64d
Clough et al. (1996) 4.9–5.5 (three soils)e
Synt
50
2.0
P, 150 d
11–35
13–21
32–48
100
4.81
P, 288 d
22–31
21–24
68–81
Lysimeter studies
Clough et al. (1998) 5.3–6.2 4.5–18.5 Synt (four soils)
ARTICLE IN PRESS
Clough et al. (2003) 4.7
Sheep 20.5
Di et al. (2002)
5.3
2.0
Decau et al. (2003)
Cow 100
5.0
P, 365 d
58, 50f
28, 25f
86, 75f
Cow 52
2.84
P, 2 y
37–49g
23–31g
67–77g
5.0
P, 1 y
58
28
86
5.3
2.0
Menneer et al. (2008) 6.0
4.2
Cow 77.5
4.65
P, 196 d
20–27
24–27
44–53
Shepherd et al. (2010)
5.9
5.6
Cow 50
5.16
P, 247 d
48
19
67
Welten et al. (2013) 5.9
8.8
Synt
4.65
P, 300 d
26
24
50
Cow 70
5.0
P, 17 months 40, 50, 18h 17, 16, 14h
47, 66, 32h
Cow 35
9.0
IR, 76 d
5
31
37
O, 96 d
5
27
32
IR, 76 d
5
20
24
O, 96 d
5
23
27
Woods et al. (2017) 5.7, 6.3 Carey et al. (2017)
6.1
4.0
100
60
70
a
NA, not applicable; G, grass (Agrostis capillaris); R, ryegrass (perennial) (Lolium perenne); P, pasture; IR, Italian ryegrass (Lolium multiflorum); O, Oats (Avena sativa). Synt, synthetic. Regular cutting twice weekly. d Data are for subsoiled and non-subsoiled treatments, respectively. e Data are for soils without a water table. f Values are for urine and urine + dairy effluent, respectively. g Range of data are for three soils (pH 8.0, 5.8, 6.7; total N, 2.4, 2.0 and 1.2 g N kg1, respectively) over 2 years. h Three pasture types (perennial ryegrass-white clover; Italian ryegrass; lucerne). b c
ARTICLE IN PRESS
Silva et al. (2005)
Table 11 Recovery of
15
N-labeled animal urine in crops and soil in field experiments. Soil Urine N added pH
Total N (g kg21)
Type
Vallis and Gardner (1984)
8.4
0.8
Cattle 12.8–26.6
g m22
Vallis et al. (1985)
6.2
0.8
Cattle 15.0
Whitehead and Bristow (1990)
6.2
3.4
Cow 74.4
5.1
0.6
5.8, 6.0 3.8, 2.7
Leterme et al. (2003) (three times, two rates) Bol et al. (2004)
1.1 5.5
Crop and duration Crop
Soil
Total
Pasture, 28 d
42–66
50–68
58
65
2–8 5–7
4.37
Grass, 321 d
23
14
37
Cattle
4.8
Pasture, 150 d
19
40
60
Sheep 12.3
4.87
Pasture, 70 da
42
33
5.23
c
Pasture, 38 d
47
29
14
23
37
4.36
Wheat, 370 d
46.1
3.78
Wheat, 240 df
17
22g
39
Sheep 7.7
3.4
Pasture, 350 d
50, 35
20, 25
70, 60
Cow 6.1, 7.5
0.87–1.02 Ryegrass, 168–350 d
49–65, 30–61
23–31, 27 77–88, 57–88
Cow 23–40
17.4
1–4
47
Pasture, 14 d
1.58
Pasture, 27 weeks
Taghizadeh-Toosi et al. (2011)
Cow 93
4.96
Pasture, 58 d
Urine applied October 19, 1992 (Experiment 3). Dry season. Urine applied September 11, 1992 (Experiment 3). d Includes 8% NH4 + + NO3 . e Urine applied November 29, 1990; wheat sown June 26, 1991 and harvested December 4, 1991 (Experiment 1). f Urine applied April 8, 1991; wheat sown June 26, 1991 and harvested December 4, 1991 (Experiment 1). g Includes 5% NH4 + + NO3 . h In microbial biomass, 2-year average. b c
76
9.8
Cow 105
a
75 d
e
Wachendorf and Joergensen (2011) 5.1 5.5
b
Pasture, 63 d
25.9
Williams and Haynes (2000)
N (atom%)
13 3
48–51 h
ARTICLE IN PRESS
Thompson and Fillery (1998)
Templeton sil
N recovery (%)
15
Reference
Williams and Haynes (1994)
15
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
25
4.3 Slurry Laboratory studies conducted with 15N-labeled slurry are summarized in Table 12. Slurry was labeled either by feeding a pig with 15N-enriched maize (Cavalli et al., 2018; Table 5), or by addition of 15 NH4 +. The soils used were all acidic and varied in total N from 0.9 to 3.2 g kg1 soil. Slurry was mixed with the soil (Aita et al., 2012; Clark et al., 2009; Paul and Beauchamp, 1995; Trehan, 1994) or surface-applied (Aita et al., 2012; Moal et al., 1994). All slurries were alkaline in pH and were applied at rates from 0.08 to 2.78 g kg1 soil (Table 12). The incubation periods lasted from 2 to 133 days (Table 12). Quantitative recovery of NH4 + -labeled slurry was obtained in two studies (Cavalli et al., 2018; Clark et al., 2009), while there was no difference in soil recovery between surface and incorporated slurry (Aita et al., 2012). Pot studies conducted with 15N-labeled slurry are also summarized in Table 12. Soils were acidic or alkaline and varied in total N from 0.9 to 2.1 g kg1 soil. Slurry was labeled by addition of 15N-enriched urea (Chadwick et al., 2001) or by addition of 15 NH4 +. Slurry was neutral, strongly alkaline or slightly acidic, and was applied at rates from 0.12 to 5.55 g kg1 soil. Slurry was either surface-applied (Chadwick et al., 2001), mixed with the soil (Dosch and Gutser, 1996; Sørensen and Jensen, 1995b; Trehan and Wild, 1993), mixed with 3/5 of the soil (Paul and Beauchamp, 1995) or applied as a “simulated injection” (Chadwick et al., 2001; Sørensen and Jensen, 1995b). Perennial and annual crops were grown for varying periods up to 64 days (Table 12). Total recoveries ranged from 33% to 97%. Recovery in herbage was consistently higher in three soils for “injected” vs mixed application (Sørensen and Jensen, 1995b), while Chadwick et al. (2001) found higher total recovery of 15N-urea in “injected” (76%) vs surface application (53%). Lysimeter studies conducted with 15N-labeled slurries are summarized in Table 13. All slurries employed in lysimeters were artificially-labeled with 15 NH+4 and were surface-applied with or without some mixing with the surface soil. The soils were either acidic or alkaline while slurries were alkaline. Total recoveries in rotation crops or pastures and soil over periods between 1 and 5 years were all <50%, indicating that labeled inorganic N rather than total slurry N per se was subject to considerable loss. Field studies conducted with 15N-labeled slurries are also summarized in Table 13. Soil pH was neutral or acidic with total N varying from 0.4 to 2.6 g kg1 soil. Slurry pH was naturally neutral to alkaline, but was also artificially adjusted with acid to give a range of pH values of 5–7 (Park et al., 2018). Various methods were used to apply slurry including surface spreading,
Table 12 Recovery of 15N-labeled animal waste slurries in crops and soil in laboratory and pot experiments. Soil Slurry N addeda g kg soil
21
pH
Total N (g kg21)
Type
Trehan (1994)
6.0
0.9
Dairy
Moal et al. (1994)
5.3
1.7
Pig
2.1
Dairy 7.5 0.35
Reference
pH
15
N (atom%)
15
N recovery (%)
b
Crop and duration
Cropb Soil
NH4+ + NO32 Total
Laboratory studies
Paul and Beauchamp (1995)
0.48 7.8
14.16
NA, 9 d
34
2.51
NA, 2 d
55
NA, 21 d
6.3, 6.0 3.2, 1.5
Pig
8.3 2.78
7.29
NA, 133 d
Aita et al. (2012)
5.2
0.9
Pig
8.2 0.08
2.76
NA, 95 d
Cavalli et al. (2018)
7.9
1.7
Pig
7.4e 0.07
2.46e
NA, 112 d
8.2f
2.01f
79 55
54
54 98 8, 105 6
5d
5d 98 1 100 1
Pot studies Trehan and Wild (1993)
6.1
Dairy
0.41
8.16
Potato, 98 d
2.1
Dairy 7.0 0.35
5.10
Maize, 5–7th leaf 57g
57
Sørensen and Jensen (1995b) 6.2–7.9 1.1–1.6 (three soils)
Cattle 6.8 0.92
1.43
Ryegrass, 180 d
60–64 23–39
77–97
Dosch and Gutser (1996)
1.2
Cattle
0.12
14.4
Oats, flowering
52
6
58
1.7
Pig
8.5 5.55
8.31
Grass, 8 d
2–7
6–8
Paul and Beauchamp (1995)
6.4
Chadwick et al. (2001)
Contained from 30% to 88% NH4 N. NA, not applicable. c Includes clay-fixed NH4 + . d In the absence of wheat straw for both surface-applied and incorporated slurry. e Raw slurry. f Digested slurry. g Two crops of maize. a
b
+
21
47
9c
0.9
25–55
77
33–70
ARTICLE IN PRESS
Clark et al. (2009)
45c
Table 13 Recovery of 15N-labeled animal waste slurries in crops and soil in lysimeter and field experiments. Soil Slurry N added Reference
pH
Total N (g kg21) Type
pH
g m22
15
N recovery (%)
15 N (atom%)
Crop and duration
Crop
Soil
Total
9.37
Pasture, 1 y
35
14
49
12–15
Rotation, 5 y
24–30
Lysimeter studies Cameron et al. (1995)
7.6
Pig Cattle
13.4
24–30
Carey et al. (1997)
7.5
3.6
Pig
7.5 20, 40
9.07
Pasture, 730 d
20, 20 17, 14 37, 34
Di et al. (1999)
5.3
2.0
Dairy
8.4 20
10.0
Pasture, 365 d
24a
24
2.1
Dairy
7.0 0.35
4.62
Maize, 125 d
15
15
Field studies Paul and Beauchamp (1995) Morvan et al. (1997)
6.2
1.3
Pig
7.4 18.4
1.46
Pasture, 27 d
41
16
57
Chadwick et al. (1998)
7.2
1.8
Pig
72.8
1.25
Pasture, 30 d
16
31
47
Sørensen and Jensen (1998)
6.8, 7.0 1.4, 0.4
Sheepb
23.8
4.58, 5.31
Barley + ryegrass, 89 d
8–59c, 33–88, 81–100, 16–60c 23–68 67–88
Jensen et al. (2000)
6.0
Cattle
15.8
2.31
Wheat, 205 d
32
Mun˜oz et al. (2003)
6.7
Petersen (2005)f
6.1
2.6 2.0
Cow Pig
22.4 7.5 13.4
e
3.22
45d e
24
e
77 41e
Corn, maturity
17
Wheat, 40–65 d
31–55
31–55
Weeds
3–30
3–30 Continued
ARTICLE IN PRESS
Gutser and Dosch (1996) 6.5
7.6 20
Table 13 Recovery of 15N-labeled animal waste slurries in crops and soil in lysimeter and field experiments.—Cont’d Soil Slurry N added Reference
pH
Total N (g kg21) Type
Sørensen and Thomsen (2005b)
6.8
1.7
Powell et al. (2005) (year 2000 crop)
6.7
Pig
pH
g m22
15 N (atom%)
10.2g, 9.2h
1.1g, 3.1h
g
h
g
15
N recovery (%)
Crop and duration
Crop
Soil
Total
Spring barley, 77 d
33, 47 53, 32 86, 79
h
12.3 , 12.1 1.11 , 1.51 Winter wheat, 324 d 40, 52 39, 21 79, 73 1.64i
30.4j
1.10j
Cattle 7.2 16.3
2.17
Barley, 54 d
45–68
45–68
Cow
17–27
0.9–1.4
Maize, maturity
10–24
10–24
Hoekstra et al. (2010)
Cattle
8.3–11.0
1.8–2.7
Pasture, 60–150 df,l
18–45 20–36 38–81
Hoekstra et al. (2011)
Cattle
19–21
0.6–1.1
Pasture, 434 d
Cow
13–17
0.5
Maize, maturity
25–33
5.37
Pasture, 56 d
20–29 40–43 60–71
Petersen (2006)
f
Cusick et al. (2006a)
6.7 k
6.7
Powell et al. (2017)
6.9
Park et al. (2018)
5.7
a
2.0
1.4
Cow
Pig
5–7 20
Eight cuts, mean of two watering regimes. Fecal N slurry (no urine). c Slurry was incorporated, injected or surface-applied. d Includes 5% NH4 + + NO3 . e 1998 crop. f Slurry was incorporated or banded. g Labeled feces + unlabeled urine. h Labeled urine + unlabeled feces. i Forage method. j Urea method. k Range of values are for years 1998–2003 inclusive. l Three cuts (May to early Sept., Spring application); two cuts (July to early Sept., Summer application). b
Maize, maturity
15
45
60
16
45
60
17–50 45–72
ARTICLE IN PRESS
23.8i
2.0
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
29
mixing (incorporation), simulated injection and surface and sub-surface banding. Slurries were generally artificially enriched by adding 15 NH4 + or CO (15NH2)2 to unlabeled slurry, although several studies were carried out with naturally labeled slurries obtained by feeding 15N-enriched herbage (Hoekstra et al., 2011; Sørensen and Jensen, 1998; Sørensen and Thomsen, 2005b) or unlabeled herbage drizzled with 15N-labeled urea solution (Hoekstra et al., 2011). Slurries composed of labeled feces + unlabeled urine or unlabeled feces + labeled urine were employed in some studies (Hoekstra et al., 2011; Sørensen and Thomsen, 2005b). Total recoveries in crops and soil were quite variable, but generally ranged between 40% and 80% (Table 13). The method of application illustrated the importance of contact between slurry and soil with greater plant recoveries for simulated slurry injection compared with mixing or surface application (Sørensen and Jensen, 1998), results consistent with the pot studies of Sørensen and Jensen (1995b) and Chadwick et al. (2001). For surfacebanded pig slurry, the recovery of labeled urinary N by 324-d winter wheat in 2002 was greater than that of labeled fecal N (52% vs 40%), while the recovery in the 0–40 cm soil depth was the opposite (21% vs 39%), resulting in similar total recoveries of 73% vs 79% (Sørensen and Thomsen, 2005b). On the other hand, Hoekstra et al. (2011) found that total slurry N in herbage and soil over two growing seasons was 45% for urine and 72% for feces, indicating less N losses from feces compared to urine over a longer time period. Slurry pH had no effect on recoveries of pig slurry labeled with 15 N-urea in herbage and soil at day 56 (Park et al., 2018). Powell et al. (2005) found that total recoveries of slurry in a corn crop + soil totaled 45% for both the forage method and the urea method in 2000 (Table 13), while in 1999 the recoveries were 46% and 49%, respectively. Such consistent results across years and methods provide strong evidence for the efficacy of natural labeling techniques that require passage of the isotope through the animal digestive system.
5. Relative efficiencies of 15N-labeled excreta and 15N-labeled synthetic fertilizer The recovery of labeled synthetic fertilizers in crops and soil has been compared with recoveries of the labeled components of excreta (feces, urine, slurry) in several studies (Table 14). Recoveries of labeled fertilizer in crops were consistently higher than recoveries of labeled feces or slurry, but differences were considerably less between labeled urine and fertilizer (Table 14).
Table 14 Relative efficiency of
15
N-labeled excreta and Soil
15
N-labeled synthetic fertilizer. N added
15
N recovery (%)
15
Total pH N (g kg21) Typea
N g m22b (atom%) Crop and duration
Trehan and Wild (1993)
6.1 0.9
CoS
(0.29)
8.16d
AS
(0.25)
8.16
SF
8.7
3.93
Barley + ryegrass, 18 months 24a
76–83a 100
AS
9.0
10.37
65b
32–40b 100
CoS
10.0
5.10
AS
10.0
4.62
CoSe
(0.92)
1.43d
(0.25)
1.50
SU
20.5
3.28
U
20.0
SU U
Sørensen et al. (1994b) (three soils) 8.0 1.8
Paul and Beauchamp (1995)
Sørensen and Jensen (1995b)
2.1
6.8 1.4
7.0 0.4
6.8 1.4
Dosch and Gutser (1996)
Thomsen et al. (1997)
6.4 1.2
6.7 1.1
6.9 1.4
Maize, field, 155 d
Totalc
21
56
77
67
23
90
15a 29b 56a
37a
93a
84b
15b
99a
51a
16a
67a
4.56
53a
13a
66a
20.5
3.28
62A
36A
98A
20.0
4.56
78B
19B
97A
CoS
(2.9)
14.4
d
52a
31a
83a
AS
(2.9)
14.4
67b
31a
98b
SS
12.0
f
AS
6.0
AS Sørensen and Jensen (1996)
Potato, 98 d
Cropc Soilc
e
SS
12.0
AS
6.0
f
3.81
Ryegrass, 6 months
Ryegrass, 162 d
Oats, flowering
Barley, 100 d
22
g
5.0
36
3.81
25g
5.0
49
ARTICLE IN PRESS
Reference
Sørensen and Jensen (1998)
7.0 0.4
SSe
11.9
4.58
e
12.1
e e
AS 6.8 1.4
SS
AS Jensen et al. (1999)
5.7 1.4
SF
6.2 1.3
6.8 1.7
77a
5.36
56b
23b
79a
11.9
4.58
8A
79A
87A
12.1
5.36
53B
36B
89A
19.4
4.41
74a
93
18.8
3.62
32b
55b
87
5.0
51c
36c
87
19.4
4.41
9A
66A
75
18.8
3.62
29B
50B
79
5.0
49C
32C
81
A N 7.3
SU
Sørensen and Thomsen (2005b)
60a
15
SF 15
17a
15
A N 7.3
PF
h
Barley 120 d + 1 cut ryegrass 9a
10.2
1.10
Barley, 120 d
PUh
9.2
1.31
47b
AN
7.5
5.52
56c
ARTICLE IN PRESS
SU 15
Barley + ryegrass, 90 d
33a
a
CoS, cow slurry; AS, ammonium sulfate; SF, sheep feces; SU, sheep urine; U, urea; SS, sheep slurry; AN, ammonium nitrate; PF, pig feces; PU, pig urine. Data in parentheses are g N kg –1 soil. c Data within a column followed by different lower- or upper-case letters are significantly different (P < 0.05). d 15 N abundance of the NH4+ fraction of the slurry. e Incorporated. f Two slurries were used; 15N-labeled feces (4.41 atom% 15N) + unlabeled urine and 15N-labeled urine (3.22 atom% 15N) + unlabeled feces. The value for the abundance of the slurry is the weighted mean. g Weighted mean recoveries from labeled feces and labeled urine. h Components of slurry. Labeled feces were mixed with unlabeled urine and labeled urine was mixed with unlabeled feces. b
15
N
ARTICLE IN PRESS 32
Phillip M. Chalk et al.
In two studies, crop and soil recoveries of ammonium nitrate (AN) were compared with both feces and urine ( Jensen et al., 1999; Sørensen and Thomsen, 2005b). Recoveries in crops were in the order of feces < urine < AN, while soil recoveries were in the order feces > urine > AN. Recoveries in crops reflect the relative availability of the organic and inorganic components of animal excreta compared with the readily available N in synthetic fertilizer. Recoveries in soil were therefore consistently greater for feces and slurry compared with synthetic fertilizer, while the differences between urine and synthetic fertilizer were less marked (Table 14). However, caution needs to be exercised when comparing recoveries of uniformly labeled fertilizer with non-uniformly labeled animal excreta. Of particular concern is the form in which the 15N enrichment of the excreta is expressed, i.e., as total or a fraction of the total N in the excreta, as in the case of 15 NH4 + or 15N-enriched urea added to unlabeled urine or slurry.
6. Interactions between synthetic fertilizer N and animal excreta N Several types of experiments have been reported. Either the N fertilizer (Table 15) or the animal excreta (Table 16) can be labeled with 15 N while the other component is unlabeled. Various N fertilizer forms and types of animal excreta have been employed, and the scale of experimentation has varied among pots, lysimeters and field microplots. The simplest design has involved a comparison of a single rate of N fertilizer with and without the addition of a single rate of animal excreta. In this case the treatment comparison involves different amounts of total N addition although the amount of excess 15N added in the two treatments is the same. In order to avoid this perceived design imperfection several authors (e.g., Lee and Choi, 2017; Li, 2013; Wu et al., 2010) adjusted the ratios of fertilizer and excreta to obtain the same amounts of total N addition. However, this latter approach can result in different amounts of 15N-labeled material (N fertilizer or excreta) between treatments which invalidate treatment comparisons of 15N recoveries in plant and soil (e.g., Lee and Choi, 2017; Li, 2013). In contrast, Wu et al. (2010) achieved the same total N input (fertilizer alone, excreta alone or fertilizer + excreta; 0.15 g N kg1 soil) and the same 15 N-labeled N input (fertilizer or excreta) by maintaining the same percentages of labeled and unlabeled components of the fertilizer or the fertilizer + excreta (e.g., 60% labeled fertilizer + 40% unlabeled fertilizer cf. 60% labeled fertilizer + 40% unlabeled excreta).
Table 15 Recoveries of
15
N-labeled fertilizers in crops and soil in the presence and absence of unlabeled animal excreta. 15 Soil Fertilizer Excreta N recovery (%)
Reference
pH g N kg21 Typea
15 N g N m22b (atom%)
Typec g N m22b
Pomares-Garcia and Pratt (1978)
6.9 0.35
(0.20)
CF
21.6
Barley (229 + 64 d)e
71
18
89
72
18
90
See footnotef
Ryegrass, 5 cuts
49a
0
Ryegrass, 1st cut
52a
92 6.0 9.2
f
15
15
A N 4
2.4
PS
5.9 11.4f Stevens et al. (1987)
0
5.8 6.5
CN
5.0
2.37
CoS
2.5 5.0 Thomsen and Kjellerup (1997)
Li et al. (2001)
Lundga˚rd soil
6.6 1.7 6.9 5.6
Thomsen (2005)
1.2
15
15
A N 5.0
AS
15
5.0
10.97
g
CF
AN
0.6
99.0
61b
47a 54a
0
Barley 1993
34a
12
Spring CM
32a
0
Barley 1994
25A
12
Autumn CM
17B
Barley (maturity)
lost
26a
9
37b 46
Barley, 130 d
35a
FYM 0 45
15
Cropd Soild Totalc,d
ARTICLE IN PRESS
Stevens et al. (1986)
AS
Crop and duration
FYM 0 28
42b Continued
Table 15 Recoveries of
15
N-labeled fertilizers in crops and soil in the presence and absence of unlabeled animal excreta.—Cont’d 15 Soil Fertilizer Excreta N recovery (%)
Reference
pH g N kg21 Typea
15 N g N m22b (atom%)
Typec g N m22b
Crop and duration
Wu et al. (2010)
5.0 0.9
(0.15)
RF
Rice, 4 months 27a
AS
42.1
7.3 1.3
0
Nannen et al. (2011)
6.2 1.6 1.9
h
5.5
15
A N 16.0
3.1
CoF
24b
40b 64b
0
49A
31A 80A
44B
41B 84B
Maize (maturity)
54a
31a
86
60a
29a
89
Maize (maturity)
55a
Pasture, 554 d 60
20
80a
80 A
55
17
74b
80 S
62
17
81a
0
h
8.8 15
A15N 5.0
1.43–3.84 CS
h
0 7–15
Buckthought et al. (2015a) 5.9 6.7
a
U
40
5.0
CoU 0
60b
AS, ammonium sulfate, AN, ammonium nitrate, CN, calcium nitrate; U, urea. Data in parentheses ( ) are g N kg– 1 soil (pot experiment); A, autumn; S, spring. CF, cattle feces; PS, pig slurry; CoS, cow slurry; FYM, farmyard manure; RF, rabbit feces; CoF, cow feces; CS, cattle slurry; CoU, cow urine. d Data within a column and soil type followed by different lower- or upper-case letters are not significantly different (P < 0.05). e Two harvests of barley (71 + 158 d), followed by Sudan grass harvested after 64 days; Rates of fertilizer and excreta were the highest of each of four rates. f Plots had been fertilized with low and high (8) rates of pig slurry for 8 years previously. g Plots had been fertilized with either 0 or farmyard manure for 9 years previously. h Plots had received cow feces at either 0 or 8.8 kg N ha1 y1 for 26 years between 1977 and 2003. b c
59a
ARTICLE IN PRESS
Nyiraneza et al. (2010)
15
32a
(0.06)
(0.06) h
Cropd Soild Totalc,d
Table 16 Recoveries of
15
N-labeled animal excreta in crops and soil in the presence and absence of unlabeled N fertilizer. 15 N recovery (%) Soil Excreta Fertilizer g N kg21 Typea g N m22b
Reference
pH
Wu et al. (2010)
5.0e 0.9e
RF
(0.15)
15
N (atom%) Typec g N m22b Crop and duration Cropd Soild Totald
19.4
AS
Nannen et al. (2011)
5.5
CS
7.2–14.8 0.73
AN
8a
69a
(0.09)
12b
51b 63b
0
15A
68A 83A
(0.09)
25B
65A 90B
0
Rice, 4 months
Maize (maturity)
5.0 Buckthought et al. (2016) 5.6
CoU 80
5.0
U
0
Pasture, 106 d
RF, rabbit feces; CS, cattle slurry; CoU, cow urine. Data in parentheses ( ) are g N kg –1 soil (pot experiment). AS, ammonium sulfate; AN, ammonium nitrate; U, urea; d Data within a column and soil type followed by different lower- or upper-case letters are significantly different (P < 0.05). e Sandy soil. f Clayey soil. b c
21a 20a
3.5 a
77a
50
33
83
52
21
73
ARTICLE IN PRESS
7.3f 1.3f
0
ARTICLE IN PRESS 36
Phillip M. Chalk et al.
Interactions have been studied with respect to several variables, including type of crop, rates of addition of N fertilizer or excreta and method and time of application of fertilizer and excreta. Interactions are examined with respect to recoveries of 15N in crops and soil (Tables 15 and 16).
6.1
15
N-labeled fertilizer + unlabeled excreta
Significantly greater recoveries of labeled ammonium sulfate fertilizer were found in pot-cultured rice in the absence of unlabeled rabbit feces, whereas recoveries in soil and total recoveries were significantly greater in the presence of feces (Wu et al., 2010; Table 15). This result was consistent across two soil types (acidic and low N, alkaline and high N). A possible explanation for such a result is stimulated microbial activity and hence greater immobilization of synthetic fertilizer in the presence of feces. A similar conclusion was reached by Di et al. (1999) where marked differences were found in leaching losses between an 15 NH4 + treatment (15–19%) compared with 5–8% in a slurry (dairy shed effluent) + 15 NH4 + treatment in a lysimeter experiment, although similar plant (perennial ryegrass + white clover) recoveries of 15N between treatments were found. On the other hand, Thomsen (2005) reported that addition of farmyard manure (FYM) in a lysimeter experiment did not affect immobilization or leaching of labeled ammonium nitrate, while FYM stimulated recovery of fertilizer by barley. Similarly, Nannen et al. (2011) found that the recovery of labeled ammonium nitrate by maize was significantly higher through addition of cow slurry (Table 15). Labeled fertilizer recoveries have been measured in plots where total soil N had increased significantly through low and high annual application rates of pig slurry for 8 years (Stevens et al., 1986), farmyard manure for 9 years (Li et al., 2001) or cow feces for 26 years (Nyiraneza et al., 2010). Plant recovery of labeled fertilizer was significantly higher at the higher compared with the lower rate of pig slurry (Stevens et al., 1986), while there were no significant differences in fertilizer recovery in maize or soil in the long-term cow feces plots (Nyiraneza et al., 2010). On the other hand, Li et al. (2001) reported significantly higher fertilizer recoveries in soil in +FYM plots compared with FYM plots, a result consistent with that of Wu et al. (2010). Several authors have reported that addition of feces or slurry had no effect on the recovery of labeled fertilizer by crops (Pomares-Garcia and Pratt, 1978; Stevens et al., 1987). Similarly, Thomsen and Kjellerup (1997) found that spring feces addition had no effect on recovery of labeled ammonium
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
37
nitrate by barley, but recovery was significantly less in the presence of feces when applied in the autumn. These results were consistent across two sites (Lundga˚rd and Ashkov). Buckthought et al. (2015a) similarly reported that the total recovery of urea in crops and soil was significantly less in the presence of cow urine applied in autumn compared with a spring application. The effects of animal excreta on the recovery of synthetic fertilizer N by crops have therefore been shown to be inconsistent, with either no effect or a positive or negative effect. The rate of excreta addition had little or no effect on N fertilizer recovery in crops and soil (Pomares-Garcia and Pratt, 1978; Stevens et al., 1987) while autumn application of excreta had a negative effect compared application in spring.
6.2
15
N-labeled excreta + unlabeled fertilizer
Fewer studies have been carried out with 15N-labeled excreta + unlabeled fertilizer (Table 16) compared with 15N-labeled fertilizer + unlabeled excreta (Table 15). The recovery of labeled rabbit feces by rice in two soils was significantly enhanced by the presence of N fertilizer (Wu et al., 2010; Table 16). On the other hand, the recovery of 15N-labeled feces in the soil was either not affected or was significantly reduced by the presence of N fertilizer. Overall, there was no consistency between the soils in the total recovery of the labeled excreta, either being greater or less in the presence of the N fertilizer (Table 16). In contrast, both Nannen et al. (2011) and Buckthought et al. (2016) found no effect of N fertilizer on the recovery of slurry N or urine N in maize or pasture, respectively (Table 16), whereas Buckthought et al. (2016) found greater recovery of labeled urine N in the soil in the absence of N fertilizer. Thus there was no consistency across soils and types of excreta in the interactions between labeled excreta and unlabeled fertilizer N.
7. Losses of N from excreta-amended soils 7.1 As ammonia and nitrous oxide emissions Losses of 15NH3 can occur during storage of labeled slurry before soil application (e.g., Beline et al., 1998). However, only direct measurements of 15 NH3 volatilization from labeled excreta added to soil are considered here. The 15NH3 volatilized from soil-applied labeled slurry may represent only a temporary loss from the soil-plant system, because a part of the loss can be reabsorbed by a plant canopy (Sommer et al., 1993).
ARTICLE IN PRESS 38
Phillip M. Chalk et al.
Similarly, although losses of N2O can occur during storage of slurry (e.g., Beline et al., 2001) only losses attendant on soil addition of excreta are considered. A review of the use of both 15N enriched and 15N natural abundance techniques to estimate N2O losses from excreta-amended soils was given by Clough et al. (2013). Studies of gaseous losses of N from labeled excreta-amended soils have been concerned almost exclusively with urine (Section 7.1.1) and slurry (Section 7.1.2). In a laboratory study with labeled feces, Ingold et al. (2018) were able to differentiate labeled NH3 and N2O from unlabeled soil sources, although quantitative recoveries of the labeled gases were not recorded. In a lysimeter experiment with labeled feces and labeled urine applied individually at the same rate (100 g N m2), Wachendorf et al. (2008) found that loss of 15N2O from urine (0.05%) was less than that from feces (0.33%) over 171 d. 7.1.1 Urine The recoveries of 15N-labeled animal urine as NH3 and N2O in laboratory, pot, lysimeter and field experiments are given in Table 17. The majority of studies were conducted with synthetic or cow urine. All but one of the soils were acidic. Generally mineral soils were used, although Clough et al. (1996, 1998) also included peat soils in their lysimeter experiments. Rates of urine N addition were commonly within the range of 50–100 g N m2, although lesser amounts were sometimes applied (Table 17). NH3 losses peaked within a few days following urine application, and 15 N recoveries were quite variable (0.7–38%). NH3 loss was directly related to soil pH (Clough et al., 2003). NH3 loss was reduced when a urease inhibitor (Agrotain) was combined with the urine (Menneer et al., 2008), but the application of two nitrification inhibitors (DCD, 4MP) had no effect. NH3 volatilization loss was also reduced by addition of biochar to soil (Taghizadeh-Toosi et al., 2012). Recoveries of urine as N2O varied from trace amounts (0.02%) to very low emissions (2%), whereas only in one case (Bertram et al., 2009) were uncharacteristically high recoveries recorded. N2O losses were reduced by the addition of the nitrification inhibitor DCD (Di and Cameron, 2008) and by the addition of biochar (Taghizadeh-Toosi et al., 2011). 7.1.2 Slurry The recoveries of 15N-labeled animal waste slurries as NH3 and N2O in pot, lysimeter and field experiments are given in Table 18. The soils used were acid to neutral and varied in total N from 1.2 to 3.6 g kg1 soil. Slurries were
Table 17 Recovery of 15N-labeled animal urine as NH3 and N2O in laboratory, pot, lysimeter and field experiments. 15 Soil Urine N addeda N recovery (%) 15 N Rate 22 (g m ) (atom%)
pH
Total N (g kg21)
Type
Bronson et al. (1999)
5.0
0.72
Sheep 20.5
Clough et al. (2003)
4.7
Reference
Crop
NH3 trap (d)
NH3
N2O
None
0–28
38
0.6b
0–12
1.2
0.4, pH 5.8–6.8
0–15
7.9
Laboratory studies
50
7.7
<2
Clough et al. (2004)
4.7
Synt
50
Bertram et al. (2009)
5.9
Cow 75
5.6–5.9
0–17
17
Taghizadeh-Toosi et al. (2012)
5.5
Cow 50.9
20
0–29
1.4, 0.8d
0–7
1.4–5.3 0.8
6–17c
Pot studies Monaghan and Barraclough (1993)
6.2
Ambus et al. (2007)
5.6
Uchida et al. (2011)
5.6
3.7
Cow Synt
6.6
Pasture 26, 51
Cow 59
5.2
Pasture
0.2, 0.3
1.00
Ryegrass
0.1–1.4e Continued
ARTICLE IN PRESS
Synt
2.0
Table 17 Recovery of 15N-labeled animal urine as NH3 and N2O in laboratory, pot, lysimeter and field experiments.—Cont’d 15 Soil Urine N addeda N recovery (%) Reference
15 N Rate 22 (g m ) (atom%)
Crop
NH3 trap (d)
NH3
5.0
Pasture
0–21
2.0
50
2.0
Pasture
0–4
0.2
100
4.81
Pasture
0–4
0.7–3.9 0.8–1.9
0–20
5g–17
pH
Total N (g kg21)
Type
5.3
2.0
Cow 100 Synt
N2O
Lysimeter studies Di et al. (2002)
Clough et al. (1996) (three soils)f 4.9–5.5
1.0–1.5
Clough et al. (1998) (four soils)
5.3–6.2 4.5–18.5 Synt
Menneer et al. (2008)
6.0
4.2
Cow 77.5
4.65
Pasture
Di and Cameron (2008)
5.8
2.0
Cow 100
5.0
Pasture
0.1h–0.4
2.3
Cow 103
1.58
Ryegrass
0.05
6.7
Cow 20, 40
5.0
Pasture
<0.04
Cow 70
5.0
Pastures
0.5–1.0
Buckthought et al. (2015b)
5.9
Woods et al. (2017)
5.7
Carey et al. (2017)
6.1
4.0
Cow 35, 70
9.0
Ryegrass 0–30
3–4
6.2
3.4
Cow 74.4
4.37
Grass
17.8
1.1
Cow 6.1, 7.5 0.87–1.02 Ryegrass 0–4
1.0–2.6 12, 14
0.9
Field studies Whitehead and Bristow (1990) Leterme et al. (2003) Bol et al. (2004)
5.5
Cow 23, 40
10.2, 17.4 Pasture
Taghizadeh-Toosi et al. (2011)
5.5
Cow 93
4.96
a
Synt, synthetic urine. Includes NO emissions. c Day 53 for N2O. d Without and with biochar, respectively. e Soil temperature range 11–23 °C. f Peat soils (10 and 20 y under pasture), mineral soil (50 y pasture). g +urease inhibitor (Agrotain). h +nitrification inhibitor (DCD). b
Pasture
0–16
0–6
0.02 0.2, 0.1d
ARTICLE IN PRESS
Wachendorf et al. (2008)
<0.07
Table 18 Recovery of 15N-labeled animal waste slurry as NH3 and N2O in pot, lysimeter and field experiments. Soil Slurry N added Reference
pH Total N (g kg21) Type
pH Rate (g m22)
15
15
N recovery (%)a
N (atom%) Crop
NH3 trap (d) NH3b
14.4
0–6
N 2O
Pot studies Cattle
7.0
Wheat
50 (S)
ARTICLE IN PRESS
Dosch and Gutser (1996) 6.4 1.2
30 (I) Chadwick et al. (2001)
1.7
Pig
8.5 2500
8.31
Grass
0–8
15 (S) 11 (I)
Lysimeter studies Carey et al. (1997) Lee et al. (2014)
3.6 Not specified
Pig Cow
7.5 20, 40 27.7
9.1c
Pasture
0–14
26, 15
Barley
0–4
4
0.41
d,e
0.43
e,f
30
0.43
e,g
2
0.40
e,h
35 Continued
Table 18 Recovery of 15N-labeled animal waste slurry as NH3 and N2O in pot, lysimeter and field experiments.—Cont’d 15 Soil Slurry N added N recovery (%)a Reference
pH Total N (g kg21) Type
pH Rate (g m22)
15
N (atom%) Crop
NH3 trap (d) NH3b
N 2O
Field studies Chadwick et al. (1998)
7.2 1.8
Pig
66
0.98i
Grass
Dittert et al. (2001)
6.0
Dairy 7.5 6.4
1.45j
Pasture
Dittert et al. (2005)
5.0 2.3
Cattle
8.2
0.73
Pasture
Lampe et al. (2006)
5.0 2.3
Cattle
7.4
0.72
Pasture
<0.1
Senbayram et al. (2009)
5.0 2.3
Cattle
48
Pasture
0.4
Park et al. (2018)
5.5 1.6
Pig
5.0 a
Data in parentheses are % of ammoniacal-N. S, surface application; I, injected (shallow). Total N; 10.25 atom% of ammoniacal-N. d High protein diet, feces component of slurry 15N enriched. e Relative values (%) were converted to absolute values (Chalk et al., 2015). f High protein diet, urine component of slurry 15N enriched. g Low protein diet, feces component of slurry 15N enriched. h Low protein diet, urine component of slurry 15N enriched. i Total N; 1.25 atom% of ammoniacal-N. j Total N; 4.29 atom% of ammoniacal-N. k Low value (+DMPP), high value (DMPP). b c
5.37
32 (52) 0.8 (1.4) 0.8–1.5k
0–5
Ryegrass 0–56
4
1.1
0.05
0.8
0.03
ARTICLE IN PRESS
7.0 20
0–8
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
43
from pigs and cattle, and were generally alkaline in pH (Tables 12, 13, and 18) which favors NH3 volatilization. Rates of applied slurry were generally <100 g m2, although an excessively high rate of 2.5 t ha1 was recorded by Chadwick et al. (2001). Recoveries of slurry as ammonia were low to high (<1–50%) and the peak loss generally occurred within a few days following slurry application. Higher losses were recorded for surface-applied slurry cf. injected (Chadwick et al., 2001; Dosch and Gutser, 1996), while volatilization was less for slurry adjusted to pH 5 with acid cf. pH 7 (Park et al., 2018). The percentage NH3 loss decreased as the rate of slurry application increased (Carey et al., 1997), although the total amounts volatilized (5–6 g N m2) were similar. Using slurry where the uniformly labeled component was either the feces or the urine, Lee et al. (2014) found that NH3 was more readily volatilized from the urine than from the feces, a result that was consistent for both low and high protein diets (Table 18). For slurry that was not uniformly labeled, the 15N recovered as NH3 depended on whether the calculation was made on the 15N enrichment of the total- or ammoniacal-N (Chadwick et al., 1998; Table 18). Recoveries of slurry as N2O varied from trace amounts (<0.1%) to very low emissions (maximum 4%). Therefore, in terms of the efficiency of slurry as a fertilizer, losses as N2O were orders of magnitude less than potential losses of NH3. However, whereas NH3 may be reabsorbed by foliage or redeposited in precipitation, N2O is lost to the atmosphere as a potent greenhouse gas, representing an environmental threat rather than an agronomic loss. Acidification of slurry reduced N2O emissions (Park et al., 2018), while emissions were also reduced through the use of a nitrification inhibitor, DMPP (Dittert et al., 2001).
7.2 As nitrate and ammonium in leachates Lysimeters have been used to obtain quantitative estimates of leaching losses of excreta N. The majority of studies have been carried out with 15N-labeled urine added to pasture swards (Table 19), although in a few cases labeled feces or slurry were used (e.g., Di et al., 1999; Thomsen et al., 1997). Experimental conditions were quite variable. Both natural cow urine and synthetic urine have been used with N application rates varying by more than 10-fold, from as little as 10.5 to as high as 137 g N m2. Urine 15N abundance varied between 1 and 5 atom%. Soil texture varied from coarse (loamy sand), coarse to medium (sandy loam), medium (loam) and medium to fine (silt loam, clay loam). The lysimeters varied in depth from 0.15 to 1.2 m. and the water
Table 19 Recovery (R) of
15
N-labeled animal urine in leachates in pasture-based lysimeter experiments. Soil Urine N added Text
McLaren et al. (1993)
sil
Fraser et al. (1994)
sil
Pakro and Dillon (1995)
sal
pH
5.8
Total N (g kg21)
2.6
Clough et al. (1996) Clough et al. (1998)
7–18.5
Silva et al. (2000)
sal
5.3
Di et al. (2002)
sal
5.3
Decau et al. (2003) (3 soils, 2 years)
Depth (m)
H2Ob (mm)
Typec g m22
Atom% 15 N
Durationd
R (%)
1.2
700
Synt
50
5.0
1y
16, 3e
1.2
1600
Synt
50
5.37
1y
8
0.15
349
Cow 109
0.97
84 d W
62
0.45
518
89
1.57
297 d Sp
13
0.15
83
137
1.17
80 d Su
54
0.30
615
Synt
50
2.0
150 d
3–52f
0.50
1583
Synt
100
4.81
406 d
13–32g
0.70 2.0
0.70
2.4, 2.0, 1.2 0.40
Decau et al. (2004)
cl
8.0
2.4
0.90
Silva et al. (2005)
l
5.3
2.0
0.70
0.3, 12h
Cow 100 600i
Cow 100
5.0
365 d
6, 9j
752, 803
Cow 52
2.84
2y
9, 15, 1k
Cow 10.5, 16.5 1.5, 2.84 2 y
0.1–27l, 0.1–22l
Cow 100
6
1162
5.0
1y
ARTICLE IN PRESS
Reference
a
Wachendorf et al. (2005)
5.9
2.7
0.80
810, 967
Cow 103
1.59
2y
64, 53
ls
6.0
4.2
0.45
663
Cow 77.5
4.65
196 d
15–24
Shepherd et al. (2010)
sil
5.9
5.6
0.50
804
Cow 50
5.16
247 d
15
Welten et al. (2013)
sal
5.9
8.8
0.60
1040
Synt
4.65
300 d
22
Woods et al. (2017)
sal
5.7, 6.3
0.70
1252
Cow 70
5.0
17 months 24, 17, 53m
Carey et al. (2017)
sil
6.1
4.0
0.70
560
Cow 35, 70
9.0
76–96 dn
31–32n, 28–33n
Carey et al. (2018)
sil
6.1
4.0
0.50
233
Cow 35
8.5
120 d
1–36o
a
60
Text, texture; sil, silt loam; sal, sandy loam; cl, clay loam; l, loam; ls, loamy sand. Precipitation + irrigation. c Synt, synthetic; N concentration of urine ranged from 5.58–15.6 g N L1 and contained from 32% to 88% NH4 + N. d Urine application in winter (W), spring (Sp) and summer (Su). e Data are for subsoiled and non-subsoiled treatments, respectively. f Range of data are for three soils (sil, sil, peat; pH 4.9–5.5) without a water table. g Range of data are for four soils (c, sil, sal, peat; pH 5.3–6.2). h Leached at 0 and 0.5 kPa suction, respectively. i Flood irrigation (100 mm 6 times at monthly intervals). j Values are for urine and urine + dairy effluent, respectively. k Data are for three soils (cl, l, sil—pH 8.0, 5.8, 6.7, respectively) each averaged over 2 years. l Range of data are for zero synthetic N fertilizer, season of application (spring, summer, autumn) and year. m Three pasture types (perennial ryegrass-white clover, Italian ryegrass, lucerne). n Treatments were oats (96 d) and Italian ryegrass (76 d), respectively. o Treatments were two temperatures, two light intensities (growth chamber), fallow or oats crop. b
ARTICLE IN PRESS
Menneer et al. (2008)
ARTICLE IN PRESS 46
Phillip M. Chalk et al.
applied either through natural rainfall or supplementary irrigation varied from 83 to 1600 mm. The experimental duration tended to be long, generally between 1 and 2 years, although it was as short as 80 d (Table 19). Given the variable nature of the experimentation, it is not surprising that there was a wide variation in the recovery of labeled urine in the leachates, from as little as <1% to as much as 60% of applied urine N. Leaching is highly site and season specific. Site variables affecting leaching include inter alia soil texture, structure, soil depth and pore size distribution, while seasonal variables include not only the total precipitation, but also its intensity and frequency, including natural rainfall and irrigation. Time is an independent variable. Given the high propensity for the downward movement of animal urine from surface-deposited urine patches, strategies have been devised and tested to limit the extent of leaching, including the use of C-rich substrates to enhance immobilization and urease and nitrification inhibitors. Shepherd et al. (2010) added either sawdust (9 t ha1) or sucrose (3, 12, 24 t ha1) to soil immediately following labeled urine application. While sawdust was not effective in reducing leaching, it was reduced by 27–66% in the +sucrose treatments, while at the same time pasture dry matter decreased by 16–29% compared to the urine alone treatment. Hence sucrose addition is not a practical method to reduce leaching. Menneer et al. (2008) tested the effect of a urease inhibitor [Agrotain, N-(n-butyl) thiophosphoric triamide] and two nitrification inhibitors (DCD, dicyandiamide; 4MP, 4 methylpyrazole) and a combination of Agrotain and DCD on the leaching of natural cow urine in a coarse-textured pumice soil. Nitrate leaching was reduced by 59% from 11.4 to 4.7 g N m2 in individual treatments of the nitrification inhibitors DCD and 4MP, but 58% of the DCD applied was recovered in leachate, illustrating its mobility or inability to be retained at the site of application in this soil. Short-term ammonia emissions (20 d) were reduced by 64% in the presence of Agrotain (7 g N m2 saved), but medium-term leaching losses increased in the presence of the urease inhibitor to 2.5 g N m2. When Agrotain was combined with DCD leaching losses were even higher at 4.5 g N m2. The major component of the leached N below 450 mm soil depth was NH4 + N which was driven by macropore processes and averaged 60% of the total N leached. Silva et al. (2000) also demonstrated NH4 + N leaching through macropores, and recommended that animals be removed from the pasture 2 days before irrigation to allow urine to diffuse into soil macropores and thus reduce leaching.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
47
Welten et al. (2013) also used a free-draining pumice soil to study the effect of DCD on the leaching of synthetic urine N. Mixing of DCD with urine before application or the spraying of DCD on the urine patch did not affect the urine leaching potential. Plant uptake of urine N increased by 32–60% and the leaching of nitrate, ammonium and dissolved organic N decreased in the presence of DCD, the extent depending mainly on the rate of application. DCD was itself leached resulting in the spatial separation of the nitrification inhibitor from the NH4 + N retained in the surface soil, and consequently represented an additional source of leached organic N, thus reducing the efficacy of DCD in reducing overall N leaching losses. The studies of Menneer et al. (2008) and Welten et al. (2013) have therefore demonstrated the potential role that nitrification inhibitors can play in protecting urinary N voided on pasture from leaching loss, but have at the same time highlighted the need for an effective yet immobile inhibitor. On the other hand the preliminary data of Menneer et al. (2008) have shown that while the urease inhibitor, Agrotain, can reduce NH3 volatilization the potential for leaching losses may increase, especially if combined with a nitrification inhibitor. Additional studies involving inhibitors combined with urine are therefore warranted. Another approach that has been tested in lysimeters to reduce leaching of N derived from urine is the planting of catch crops in situations where intensive winter forage grazing leads to high drainage losses (Carey et al., 2017, 2018). The sowing of an oats catch crop reduced nitrate leaching by 25% during the critical winter-spring drainage period compared with an Italian ryegrass cover crop (Carey et al., 2017), although relatively small amounts of 15N-urine were recovered by the catch crops (3–4%). Similar encouraging results were also obtained by Carey et al. (2018), who concluded that further research is needed to show that a catch crop can be sown successfully in most years at the farm paddock scale across a range of soil conditions.
8. The residual value of excreta N in crop sequences The residual value of various types of 15N-labeled excreta (feces, urine, slurry) was determined for several crops (cereals, grasses) grown in sequence (Table 20). As pointed out by Smith and Chalk (2018), the residual value of 15N-labeled fertilizer can be expressed as the percentage plant recovery of the labeled N added at the beginning of the crop sequence or
Table 20 Residual value of
15
N-labeled animal excreta in crop rotations or in sequential cuts of pasture species. Soil Excreta Plant recovery (%)a pH g N kg21 Typeb gN m22c
Reference
Thomsen et al. (1997)
2.1 6.7 1.1
CoS SS
10
N (atom%) R0
5.10
12
d
4.41, 3.22
6.9 1.4 Jensen et al. (1999)
5.7 1.4
SF
19.4
4.44
6.2 1.3 5.7 1.4
SU
18.4
3.62
6.2 1.3 Sørensen and Amato (2002)
f
6.4 1.4
PS
10.35–11.0 5.43–5.74
7.8 1.6 Sørensen (2004)g Powell et al. (2005)
6.4 1.4 6.7 2.0
Sørensen and Thomsen (2005b) 6.8 1.7
CoS
18.4
CoS
24–30
PS
9.7
0.64–1.6 0.84
R2
R3
Total
M, 42
M, 15
57
B, 22
B, 4
26
25
3
28
B + R, 8.5 R, 4.4
R, 2.0
15
9.0
3.8
1.1
14
32
3.3
1.3
37
29
3.8
1.3
34
B, 6.6
R, 2.5
B, 3.7
R, 1.9
15
4.9
1.9
3.5
1.5
12
B, 5.4–6.5 R, 1.9–2.2 B, 2.9–3.4 R, <2.0
3.4–3.7 h
e
R1a
h
M, 14–16h M, 4–8h B, 42
R, 1.8
18–23h B, 3.4
47
ARTICLE IN PRESS
Paul and Beauchamp (1995)
15
Cusick et al. (2006a)i
6.7 2.0
CoS
17–27
0.9–1.4
M, 10–24
M, 4–8
Wu et al. (2010)
5.0 0.9
RF
(0.15)
19.4
Rice, 8
Wheat, 8
16
15
5
20
Cotton, 7
21
10
38
Maize, 7
12
7
26
5
39
7.3 1.3 Primo et al. (2014)
6.7 0.5
GF
(0.10)
2.35
M, 1–3
Powell et al. (2017) a
6.9 1.4
CoS
13–17
0.5
M, 25–33
j
M, 5–6
j
M, maize; B, barley, R, ryegrass; CoS, cow slurry; SS, sheep slurry; SF, sheep feces; SU, sheep urine; BYM, barnyard manure; PS, pig slurry; RF, rabbit feces; GM, goat feces. c Data in parentheses are g N kg1 soil. d15 N abundance of the ammonium fraction of the slurry. e15 N abundance of the feces and urine fractions of the slurry, respectively. f Recovery data are means of all treatments (slurry mixed, injected, surface-applied). g Recovery data are ranges of values for all treatments (slurry mixed, injected, surface-applied). h Range of values are for years 1999 and 2000 and for the forage method and the urea method. i Range of values are for initial years 1998–2001 inclusive. j Range for four slurries. b
31–38j
ARTICLE IN PRESS
Cowpea, 8 26 j
19–34
ARTICLE IN PRESS 50
Phillip M. Chalk et al.
as a percentage of the residual 15N label in the soil at the beginning of each crop. The latter method corrects for the fertilizer N removed in the above-ground biomass or lost from the soil-plant system by leaching or denitrification, and is therefore not available to the subsequent crops. When losses are significant, this method of calculation is preferred to calculate the recovery of the residual N in the soil-plant system (Smith and Chalk, 2018). Olesen et al. (2004) summarized the results of experiments conducted in Denmark between 1994 and 2002, which included a range of 15N-labeled feces and urine from ruminants and pigs, either in slurry or solid feces, and applied to spring barley or winter wheat. 15N recoveries by crops in the application year were quite variable ranging from 9% to 47%, but were more consistent in the first (2.5–6%) and second (1.1–2.5%) residual years. Plant recovery of excreta N in the first (R0) and subsequent years (R1–R3) was largely dependent on the type of excreta. Recovery of sheep urine in R0 in two soils was close to 30%, decreasing to 3–4% in R1 and 1% in R2 ( Jensen et al., 1999; Table 20). The recoveries of feces N in R0 were relatively low (7–15%; Table 20), with either an increase in R1 (Primo et al., 2014) or a gradual decline in R1 and R2 ( Jensen et al., 1999), suggesting a higher residual value of feces. Compared with synthetic N fertilizers, feces had lower recoveries in R0 and R1 but higher recoveries in R2 and R3 (Smith and Chalk, 2018), reflecting the slow N release characteristics of feces. In contrast, recovery of 15N-labeled animal slurry in R0 was either high (Paul and Beauchamp, 1995; Thomsen et al., 1997) or low (Sørensen, 2004; Sørensen and Amato, 2002), which to some extent may reflect the relative proportions of feces and urine in the slurry. For example, in the study of Thomsen et al. (1997) the slurry was composed of either labeled urine + unlabeled feces or labeled feces + unlabeled urine. Crop recovery of labeled feces in R0 was 12–14% in two soils while recovery of labeled urine was 32–36%. In R1, recoveries of all labeled moieties were from 3% to 4%. The residual value of animal excreta was studied with the dynamic simulation model FAS-SET (Berntsen et al., 2007), which was validated with 1–3 years of data from three field experiments differing in several agronomic, edaphic and environmental variables. The model predicted that the type of excreta influenced the residual N value, which was reduced by wet climates, sandy soils and short-season crops, but not by the soil organic matter level.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
9. Partial
15
51
N balance
15
N balance studies involve an accounting of labeled N inputs via feces, urine or slurry and outputs comprising crop uptake, leaching of ammonium + nitrate, and gaseous emissions of NH3 and N2O as well as residual 15N excess in the soil. The added isotope which cannot be accounted for (i.e., labeled inputs—outputs) is assumed to represent losses, mainly as emission of N2, that cannot be readily measured in an open system. A tabular summary of 15N balances of labeled urine applied to swards of grasses and legumes worldwide was presented by Woods et al. (2017). The summary included data from 29 studies in 7 countries including 15N recoveries in plants, soil, leachates and gaseous NH3 and N2O losses. Of these 29 studies, 22 have been cited in the present review, with others (e.g., theses, unlabeled and 15N natural abundance studies, and labeled urea as a urine substitute) being excluded. Of these 22, we could identify only one study (Clough et al., 1998) where all inputs/outputs mentioned above were measured. Over a measurement period of 406 days with urine applied at 1000 kg N ha1 in winter to a perennial ryegrass-white clover sward, the total recoveries ranged from 68 (peat soil) to 81% (clay soil) with intermediate values for a sandy loam and a silt loam. Thus, despite the considerable effort to comprehensively measure all 15N-labeled outputs in an open field situation some 20–30% of added urine N remained unaccounted for. These findings contrast with results obtained in closed systems in which quantitative recoveries of 15N labeled fertilizer added to soils were obtained in organic, inorganic and gaseous phases both under anaerobic conditions in the laboratory (Chen et al., 1995) and aerobic conditions in the glasshouse (Clough et al., 2001).
10. Conclusions An extensive literature exists on the fate of 15N-enriched animal excreta in the soil-plant-atmosphere system, which has grown exponentially over the past 21 years since the publication of the last comprehensive review by Dittert et al. (1998). A major concern with the interpretation and comparison of data is the degree of isotopic uniformity both within and between the solid (feces) and liquid (urine) components of excreta and their admixture (slurry). Only limited attention has so far been given to the assessment of errors associated with the non-uniform distribution of isotope, particularly in urine and slurry.
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The feeding of 15N-enriched forage, silage or grain to animals is the best guarantee of obtaining isotopic uniformity in feces and urine, but this approach is time-consuming, complicated and expensive. For example, Powell et al. (2017) fed four 15N-enriched diets to three milking cows per diet over a period of 2–4 days which required a daily dry matter intake of 25 kg per cow. This exercise required detailed calculations of land area, amounts of 15N-labeled fertilizer, predicted crop yield, crop N uptake and N fertilizer use efficiency, in order to provide sufficient labeled materials, which varied in 15N abundance from 0.74 to 2.40 atom% 15N. The processing and storage of the feed components and the collection and storage of excreta four times per day for 4 days from individual cows added to the logistics attendant on this approach. For example, Powell et al. (2017) generated 324 15N-enriched samples of feces with an equal number of labeled urine samples. Specialized equipment such as indwelling catheters were also used to ensure separation of feces and urine (Powell et al., 2017), thus increasing the cost and degree of sophistication. Nevertheless, the use of 15N-enriched animal excreta has provided quantitative data on many of the processes that affect the use efficiency of these organic sources of N by crops and pastures. One advantage of the use of animal feces as a source of N for crop and pasture growth is its slow release characteristic. We obtained evidence that although initial recovery in a crop sequence may be less compared with a synthetic fertilizer, the residual value may be higher. Similar agronomic and environmental issues surround the use of both synthetic fertilizers and excreta as sources of N for plant nutrition, although the processes may differ in intensity both spatially and temporally. Of general concern are emissions of NH3 and N2O, and leaching of inorganic N. While losses of N2O are generally a small fraction of the N applied, and therefore of little effect on fertilizer use efficiency, they are nevertheless of great significance due to the potency of N2O as a greenhouse gas. Although there is little doubt that the use of 15N-enriched excreta to trace N dynamics in agroecosystems adds another layer of complexity to the evaluation of N use efficiency, without this technology we would not have the quantitative body of data we now possess regarding the efficacy of animal excreta as an organic N source, its losses and mitigation strategies. Only limited attention has been given to the alternative approach of using 15 N natural abundance (NA) as a tracer of animal excreta N dynamics (Chalk et al., 2019). For example, there are indications that under some conditions changes in the δ15N signature of substrates could indirectly indicate the extent of NH3 volatilization. Chalk et al. (2019) concluded that more
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research is needed in this area in relation to the composting of agricultural wastes, the storage and treatment of animal excreta and animal excreta voided on pastures. While farmers can exert some control over rate, placement and timing of synthetic N fertilizer application, there is little opportunity for control of excreta deposition under conditions of extensive grazing. However, under intensive animal feeding operations there may be more scope for management of excreta in order to reduce NH3 volatilization, by modifying bedding materials (Sun et al., 2016). Because of the random deposition of excreta under extensive grazing, control of nitrate leaching from urine through the use of a nitrification inhibitor is unlikely to succeed unless it can be fed to the animal (e.g., Minet et al., 2016). The alternative use of catch crops is another little-explored possibility to reduce leaching losses under extensive systems of grazing.
Acknowledgments The authors wish to acknowledge the sustained and substantial contributions from several groups of scientists worldwide: In Denmark (e.g., Sørensen, Thomsen and colleagues at various institutions); in Germany (e.g., Dittert and colleagues at various institutions); in the United States (e.g., Powell, Kelling and colleagues at the University of Wisconsin); and in New Zealand (e.g., Cameron, Di, Clough, Sherlock, Ledgard and colleagues at Lincoln University and AgResearch), who collectively have made many outstanding contributions to this field of study.
References Abdelhamid, M., Horiuchi, T., Oba, S., 2004. Nitrogen uptake by fababean from 15Nlabeled oilseed-rape residue and chicken manure with ryegrass as a reference crop. Plant Prod. Sci. 7, 371–376. Aita, C., Recous, S., Cargnin, R.H.O., da Luz, L.P., Giacomini, S.J., 2012. Impact on C and N dynamics of simultaneous application of pig slurry and wheat straw, as affected by their initial locations in soil. Biol. Fertil. Soils 48, 633–642. Ambus, P., Petersen, S.O., Soussana, J.-F., 2007. Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling. Agric. Ecosyst. Environ. 121, 84–92. Ayadi, F.Y., Cortus, E.L., Clay, D.E., Hansen, S.A., 2015. Isotope ratio mass spectrometry monitoring of nitrogen volatilization from beef cattle feces and 15N-labeled synthetic urine. Atmosphere 6, 641–649. Barkle, G.F., Stenger, R., Brown, T.N., Ledgard, S.F., Painter, D.J., 2001. Fate of 15Nlabeled feces fraction of dairy farm effluent (DFE) irrigated onto soils under different water regimes. Nutr. Cycl. Agroecosyst. 59, 85–93. Barros, T., Powell, J.M., Danes, M.A.C., Aguerre, M.J., Wattiaux, M.A., 2017. Relative partitioning of N from alfalfa silage, corn silage, corn grain and soybean meal into milk, urine, and feces, using stable 15N isotope. Anim. Feed Sci. Technol. 229, 91–96. Beline, F., Martinez, J., Marol, C., Guiraud, G., 1998. Nitrogen transformations during anaerobically stored 15N-labeled pig slurry. Bioresour. Technol. 64, 83–88.
ARTICLE IN PRESS 54
Phillip M. Chalk et al.
Beline, F., Martinez, J., Marol, C., Guiraud, G., 2001. Application of the 15N technique to determine the contributions of nitrification and denitrification to the flux of nitrous oxide from aerated pig slurry. Water Res. 35, 2774–2778. Bergstr€ om, L.F., Kirchmann, H., 1999. Leaching of total nitrogen from nitrogen-15-labeled poultry manure and inorganic nitrogen fertilizer. J. Environ. Qual. 28, 1283–1290. Berntsen, J., Petersen, B.M., Sørensen, P., Olesen, J.E., 2007. Simulating residual effects of animal manures using 15N isotopes. Plant Soil 290, 173–187. Bertram, J.E., Clough, T.J., Sherlock, R.R., Condron, L.M., O’Callaghan, M., Well, N.S., Ray, J.L., 2009. Hippuric acid and benzoic acid inhibition of urine derived N2O emissions from soil. Glob. Chang. Biol. 15, 2067–2077. Bol, R., Petersen, S.O., Christofides, C., Dittert, K., Hansen, M.N., 2004. Short-term N2O, CO2, NH3 fluxes, and N/C transfers in a Danish grass-clover pasture after simulated urine deposition in autumn. J. Plant Nutr. Soil Sci. 167, 568–576. Bosshard, C., Frossard, E., Dubois, D., M€ader, P., Manolov, I., Oberson, A., 2008. Incorporation of nitrogen-15-labeled amendments into physically separated soil organic matter fractions. Soil Sci. Soc. Am. J. 72, 949–959. Bosshard, C., Sørensen, P., Frossard, E., Dubois, D., M€ader, P., Nanzer, S., Oberson, A., 2009. Nitrogen use efficiency of 15N-labeled sheep manure and mineral fertilizer applied to microplots in long-term organic and conventional cropping systems. Nutr. Cycl. Agroecosyst. 83, 271–287. Bosshard, C., Oberson, A., Leinweber, P., Jandl, G., Knicker, H., Wettstein, H.-R., Kreuzer, M., Frossard, E., 2011. Characterization of fecal nitrogen forms produced by a sheep fed with 15N labeled ryegrass. Nutr. Cycl. Agroecosyst. 90, 355–368. Bronson, K.F., Sparling, G.P., Fillery, I.R.P., 1999. Short-term N dynamics following application of 15N-labeled urine to a sandy soil in summer. Soil Biol. Biochem. 31, 1049–1057. Buckthought, L.E., Clough, T.J., Cameron, K.C., Di, H.J., Shepherd, M.A., 2015a. Urine patch and fertiliser N interaction: effects of fertiliser rate and season of urine application on nitrate leaching and pasture N uptake. Agric. Ecosyst. Environ. 203, 19–28. Buckthought, L.E., Clough, T.J., Cameron, K.C., Di, H.J., Shepherd, M.A., 2015b. Fertiliser and seasonal urine effects on N2O emissions from the urine-fertiliser interface of a grazed pasture. N. Z. J. Agric. Res. 58, 311–324. Buckthought, L.E., Clough, T.J., Cameron, K.C., Di, H.J., Shepherd, M.A., 2016. Plant N uptake in the periphery of a bovine urine patch: determining the ‘effective area’. N. Z. J. Agric. Res. 59, 122–140. Cameron, K.C., Rate, A.W., Carey, P.L., Smith, N.P., 1995. Fate of nitrogen in pig effluent applied to a shallow stony pasture soil. N. Z. J. Agric. Res. 38, 533–542. Carey, P.L., Rate, A.W., Cameron, K.C., 1997. Fate of nitrogen in pig slurry applied to a New Zealand pasture soil. Aust. J. Soil Res. 35, 941–959. Carey, P.L., Cameron, K.C., Di, H.J., Edwards, G.R., 2017. Comparison of nitrate leaching from oats and Italian ryegrass catch crops following simulated winter forage grazing: a field lysimeter study. N. Z. J. Agric. Res. 60, 298–318. Carey, P.L., Cameron, K.C., Di, H.J., Edwards, G.R., 2018. Does sowing an oats catch crop reduce nitrate leaching from urine deposition following simulated winter forage grazing? A growth chamber experiment. Plant Soil 431, 37–52. Carter, M.S., 2007. Contribution of nitrification and denitrification to N2O emissions from urine patches. Soil Biol. Biochem. 39, 2091–2102. Catchpoole, D.W., Blair, G.J., 1990. Forage tree legumes. III. Release of nitrogen from leaf, feces and urine derived from Leucaena and Gliricidia leaf. Crop Pasture Sci. 41, 539–547. Cavalli, D., Bechini, L., Di Matteo, A., Corti, M., Ceccon, P., Gallina, P.M., 2018. Nitrogen availability after repeated additions of raw and anaerobically digested 15N-labelled pig slurry. Eur. J. Soil Sci. 69, 1044–1055.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
55
Chadwick, D.R., van der Weerden, T., Martinez, J., Pain, B.F., 1998. Nitrogen transformations and losses following pig slurry applications to a natural soil filter system (solepur process) in Brittany, France. J. Agric. Eng. Res. 69, 85–93. Chadwick, D.R., Martinez, J., Marol, C., Beline, F., 2001. Nitrogen transformations and ammonia loss following injection and surface application of pig slurry: a laboratory experiment using slurry labeled with 15N-ammonium. J. Agric. Sci. (Camb.) 136, 231–240. Chalk, P.M., Magalha˜es, A.M.T., Ina´cio, C.T., 2013. Towards an understanding of the dynamics of compost N in the soil-plant-atmosphere system using 15N tracer. Plant Soil 362, 373–388. Chalk, P.M., Ina´cio, C.T., Magalha˜es, A.M.T., 2014. From fertilizer to food: tracing N dynamics in conventional and organic farming systems using 15N natural abundance. In: Heng, L.K., Sakadevan, K., Dercon, G., Nguyen, M.L. (Eds.), Managing Soils for Food Security and Climate Change Adaptation and Mitigation. FAO, Rome, pp. 339–348. http://www-naweb.iaea.org/nafa/swmn/public/ManagingSoilFoodSecurity ProceedingsFAO-6.pdf. Chalk, P.M., Ina´cio, C.T., Craswell, E.T., Chen, D., 2015. On the usage of absolute (x) and relative (δ) values of 15N abundance. Soil Biol. Biochem. 85, 51–53. Chalk, P.M., Ina´cio, C.T., Chen, D., 2019. An overview of contemporary advances in the usage of 15N natural abundance (δ15N) as a tracer of agro-ecosystem N cycle processes that impact the environment. Agric. Ecosyst. Environ. 283, 106570. Chantigny, M.H., Angers, D.A., Morvan, T., Pomar, C., 2004a. Dynamics of pig slurry nitrogen in soil and plant as determined with 15N. Soil Sci. Soc. Am. J. 68, 637–643. Chantigny, M.H., Angers, D.A., Pomar, C., Morvan, T., 2004b. The use of 15N-enriched feed to label pig excreta for N cycling studies. Can. J. Soil Sci. 84, 43–48. Chen, D.L., Chalk, P.M., Freney, J.R., 1995. Distribution of reduced products of 15Nlabelled nitrate in anaerobic soils. Soil Biol. Biochem. 27, 1539–1545. ., 2009. Nitrogen Clark, K., Chantigny, M.H., Angers, D.A., Rochette, P., Parent, L.-E transformations in cold and frozen agricultural soils following organic amendments. Soil Biol. Biochem. 31, 348–356. Clough, T.J., Kelliher, F.M., 2005. Dairy farm effluent effects on urine patch nitrous oxide and carbon dioxide emissions. J. Environ. Qual. 34, 979–986. Clough, T.J., Sherlock, R.R., Cameron, K.C., Ledgard, S.F., 1996. Fate of urine nitrogen on mineral and peat soils in New Zealand. Plant Soil 178, 141–152. Clough, T.J., Ledgard, S.F., Sprosen, M.S., Kear, M.J., 1998. Fate of 15N labeled urine on four soil types. Plant Soil 199, 195–203. Clough, T.J., Sherlock, R.R., Cameron, K.C., Stevens, R.J., Laughlin, R.J., M€ uller, C., 2001. Resolution of the 15N balance enigma? Aust. J. Soil Res. 39, 1419–1431. Clough, T.J., Sherlock, R.R., Kelliher, F.M., 2003. Can liming mitigate N2O fluxes from a urine-amanded soil? Aust. J. Soil Res. 41, 439–457. Clough, T.J., Kelliher, F.M., Sherlock, R.R., Ford, C.D., 2004. Lime and soil moisture effects on nitrous oxide emissions from a urine patch. Soil Sci. Soc. Am. J. 68, 1600–1609. Clough, T.J., M€ uller, C., Laughlin, R.J., 2013. Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems. Animal 7 (s2), 418–426. Cusick, P.R., Kelling, K.A., Powell, J.M., Mun˜oz, G.R., 2006a. Estimates of residual dairy manure nitrogen availability using various techniques. J. Environ. Qual. 35, 2170–2177. Cusick, P.R., Powell, J.M., Kelling, K.A., Hensler, R.F., Mun˜oz, G.R., 2006b. Dairy manure N mineralization estimates from incubations and litterbags. Biol. Fertil. Soils 43, 145–152.
ARTICLE IN PRESS 56
Phillip M. Chalk et al.
de Klein, C.M., van Logtestijn, R.S.P., 1994. Denitrification and N2O emission from urineaffected grassland soil. Plant Soil 163, 235–241. Decau, M.L., Simon, J.C., Jacquet, A., 2003. Fate of urine nitrogen in three soils throughout a grazing season. J. Environ. Qual. 32, 1405–1413. Decau, M.L., Simon, J.C., Jacquet, A., 2004. Nitrate leaching under grassland as affected by mineral N fertilization and cattle urine. J. Environ. Qual. 33, 637–644. Di, H.J., Cameron, K.C., 2008. Sources of nitrous oxide from 15N-labeled animal urine and urea fertilizer with and without a nitrification inhibitor, dicyandiamide (DCD). Aust. J. Soil Res. 46, 76–82. Di, H.J., Cameron, K.C., Moore, S., Smith, N.P., 1999. Contributions to nitrogen leaching and pasture uptake by autumn-applied dairy effluent and ammonium fertilizer labeled with 15N isotope. Plant Soil 210, 189–198. Di, H.J., Cameron, K.C., Silva, R.G., Russell, J.M., Barnett, J.W., 2002. A lysimeter study of the fate of 15N-labeled nitrogen in cow urine with or without farm dairy effluent in a grazed dairy pasture soil under flood irrigation. N. Z. J. Agric. Res. 45, 235–244. Dijkstra, J., Oenema, O., van Groenigen, J.W., Spek, J.W., van Vuuren, A.M., Bannink, A., 2013. Diet effects on urine composition of cattle and N2O emissions. Animal 7, 292–302. Dittert, K., Goerges, T., Sattelmacher, B., 1998. Nitrogen turnover in soil after application of animal manure and slurry as studied by the stable isotope 15N: a review. J. Plant Nutr. Soil Sci. 161, 453–463. Dittert, K., Bol, R., King, R., Chadwick, D., Hatch, D., 2001. Use of a novel nitrification inhibitor to reduce nitrous oxide emission from 15N-labeled dairy slurry injected into soil. Rapid Commun. Mass Spectrom. 15, 1291–1296. Dittert, K., Lampe, C., Gasche, R., Butterbach-Bahl, K., Wachendorf, M., Papen, H., Sattelmacher, B., Taube, F., 2005. Short-term effects of single or combined application of mineral N fertilizer and cattle slurry on the fluxes of radiatively active trace gases from grassland soil. Soil Biol. Biochem. 37, 1665–1674. Dosch, P., Gutser, R., 1996. Reducing N losses (NH3, N2O, N2) and immobilization from slurry through optimized application techniques. Nutr. Cycl. Agroecosyst. 43, 165–171. Fraser, P.M., Cameron, K.C., Sherlock, R.R., 1994. Lysimeter study of the fate of nitrogen in animal urine returns to irrigated pasture. Eur. J. Soil Sci. 45, 439–447. Garza, H.M.Q., Delgado, J.A., Wong, J.A.C., Lindemann, W.C., 2009. 15N uptake from manure and fertilizer sources by three consecutive crops under controlled conditions. Rev. Bras. Ci^enc. Solo 33, 1249–1258. Gutser, R., Dosch, P., 1996. Cattle-slurry—15N turnover in long-term lysimeter trial. In: Rodrigues-Barrueco, C. (Ed.), Fertilizers and Environment. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 345–350. Haynes, R.J., Williams, P.H., 1993. Nutrient cycling and soil fertility in the grazed pasture ecosystem. Adv. Agron. 49, 119–199. He, D.-Y., Xing, T.-X., Zhou, W.-J., He, L.-H., Liao, X.-L., 1992. Fate and transformation of nitrogen from 15N-labeled rice straw after feeding goat. Pedosphere 2, 161–170. He, D.-Y., Liao, X.-L., Xing, T.-X., Zhou, W.-J., Fang, Y.-J., He, L.-H., 1994. The fate of nitrogen from 15N-labeled straw and green manure in soil-crop-domestic animal systems. Soil Sci. 158, 65–73. Hoekstra, N.J., Lalor, S.T.J., Richards, K.G., O’Hea, N., Lanigan, G.J., Dyckmans, J., Schulte, R.P.O., Schmidt, O., 2010. Slurry 15NH4-N recovery in herbage and soil: effects of application method and timing. Plant Soil 330, 357–368. Hoekstra, N.J., Lalor, S.T.J., Richards, K.G., O’Hea, N., Dungait, J.A.J., Schulte, R.P.O., Schmidt, O., 2011. The fate of slurry-N fractions in herbage and soil during two growing seasons following application. Plant Soil 342, 83–96.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
57
Holbeck, B., Amelung, W., Wolf, A., S€ udekum, K.-H., Schloter, M., Welp, G., 2013. Recoveries of 15N-labeled fertilizers (chicken manure, mushroom compost and potassium nitrate) in arable topsoil after autumn application to winter cover crops. Soil Tillage Res. 130, 120–127. Ina´cio, C.T., Chalk, P.M., 2017. Principles and limitations of stable isotopes in differentiating organic and conventional foodstuffs: 2. Animal products. Crit. Rev. Food Sci. Nutr. 57, 181–196. Ina´cio, C.T., Chalk, P.M., Magalha˜es, A.M.T., 2015. Principles and limitations of stable isotopes in differentiating organic and conventional foodstuffs: 1. Plant products. Crit. Rev. Food Sci. Nutr. 55, 1206–1218. Ingold, M., Khanal, G., Dyckmans, J., Wachendorf, C., 2018. NH3 volatilization, N2O emission and microbial biomass turnover from 15N-labeled manure under laboratory conditions. Commun. Soil Sci. Plant Anal. 49, 537–551. Jayasundara, S., Wagner-Riddle, C., Parkin, G., Lauzon, J., Fan, M.Z., 2010. Transformations and losses of swine manure 15N as affected by application timing at two contrasting sites. Can. J. Soil Sci. 90, 55–73. Jensen, B., Sørensen, P., Thomsen, I.K., Jensen, E.S., Christensen, B.T., 1999. Availability of nitrogen in 15N-labeled ruminant manure components to successively grown crops. Soil Sci. Soc. Am. J. 63, 416–423. Jensen, L.S., Pedersen, I.S., Hansen, T.B., Nielsen, N.E., 2000. Turnover and fate of 15Nlabeled cattle slurry ammonium-N applied in the autumn to winter wheat. Eur. J. Agron. 12, 23–35. Kirchmann, H., 1990. Nitrogen interactions and crop uptake from fresh and composted 15Nlabeled poultry manure. Eur. J. Soil Sci. 41, 379–385. Kirchmann, H., 1991. Carbon and nitrogen mineralization of fresh, aerobic and anaerobic animal manures during incubation with soil. Swed. J. Agric. Res. 21, 165–173. Lampe, C., Dittert, K., Sattelmacher, B., Wachendorf, M., Loges, R., Taube, F., 2006. Sources and rates of nitrous oxide emissions from grazed grassland after application of 15 N-labeled mineral fertilizer and slurry. Soil Biol. Biochem. 38, 2602–2613. Langmeier, M., Frossard, E., Kreuzer, M., M€ader, P., Dubois, D., Oberson, A., 2002. Nitrogen fertilizer value of cattle manure applied on soils originating from organic and conventional farming systems. Agronomie 22, 789–800. Lee, J., Choi, H.L., 2017. The dynamics of nitrogen derived from a chemical nitrogen fertilizer with treated swine slurry in paddy soil-plant systems. PLoS One 12 (3), e1074747. Lee, C., Feyereisen, G.W., Hristov, A.N., Dell, C.J., Kaye, J., Beegle, D., 2014. Effects of dietary protein concentration on ammonia volatilization, nitrate leaching, and plant nitrogen uptake from dairy manure applied to lysimeters. J. Environ. Qual. 43, 398–408. Leterme, P., Barre, C., Vertes, S., 2003. The fate of 15N from dairy cow urine under pasture receiving different rates of N fertilizer. Agronomie 23, 609–616. Li, S., 2013. Substitution effect of pig manure for nitrogen fertilizer on nitrogen-use efficiency. Commun. Soil Sci. Plant Anal. 44, 2701–2712. Li, K., Shiraiwa, T., Inamura, T., Saitoh, K., Horie, T., 2001. Recovery of 15N-labeled ammonium by barley and maize grown on the soils with long-term application of chemical and organic fertilizers. Plant Prod. Sci. 4, 29–35. Liu, J., Xie, Q., Shi, Q., Li, M., 2008. Rice uptake and recovery of nitrogen with different methods of applying 15N-labeled chicken manure and ammonium sulphate. Plant Prod. Sci. 11, 271–277. Martı´nez-Alca´ntara, B., Martı´nez-Cuenca, M.-R., Ferna´ndez, C., Legaz, F., Quin˜ones, A., 2016a. Production of 15N-labeled liquid organic fertilizers based on manure and crop residue for use in fertigation studies. PLoS One 11 (3), e0150851.
ARTICLE IN PRESS 58
Phillip M. Chalk et al.
Martı´nez-Alca´ntara, B., Martı´nez-Cuenca, M.-R., Bermejo, A., Legaz, F., Quin˜ones, A., 2016b. Liquid organic fertilizers for sustainable agriculture: nutrient uptake of organic versus mineral fertilizers in citrus trees. PLoS One 11 (10), e0161619. McLaren, R.G., Cameron, K.C., Fraser, P.M., 1993. A comparison of the effects of subsoiling on plant uptake and leaching losses of sulphur and nitrogen from a simulated urine patch. Plant Soil 155/156, 375–378. Menneer, J.C., Ledgard, S.F., Sprosen, M., 2008. Soil N process inhibitors after nitrogen leaching dynamics in a pumice soil. Aust. J. Soil Res. 46, 323–331. Minet, E.P., Ledgard, S.F., Lanigan, G.J., Murphy, J.B., Grant, J., Hennessy, D., Lewis, E., Forrestal, P., Richards, K.G., 2016. Mixing dicyandiamide (DCD) with supplementary feeds for cattle: an effective method to deliver a nitrification inhibitor in urine patches. Agric. Ecosyst. Environ. 231, 114–121. Moal, J.-F., Martinez, J., Marol, C., Guiraud, G., 1994. A direct incorporation of N-15 labeled ammonium sulphate into a pig slurry: a laboratory experiment on NH3 volatilization. Bioresour. Technol. 48, 87–89. Monaghan, R.M., Barraclough, D., 1993. Nitrous oxide and dinitrogen emissions from urine-affected soil under controlled conditions. Plant Soil 151, 127–138. Morvan, T., Leterme, P., Arsene, G.G., Mary, B., 1997. Nitrogen transformations after the spreading of pig slurry on bare soil and ryegrass using 15N-labeled ammonium. Eur. J. Agron. 7, 181–188. Mun˜oz, G.R., Powell, J.M., Kelling, K.A., 2003. Nitrogen budget and soil N dynamics after multiple applications of unlabeled or 15nitrogen-enriched dairy manure. Soil Sci. Soc. Am. J. 67, 817–825. Mun˜oz, G.R., Kelling, K.A., Powell, J.M., Speth, P.E., 2004. Comparison of estimates of first-year dairy manure nitrogen availability or recovery using nitrogen-15 and other techniques. J. Environ. Qual. 33, 719–727. Nannen, D.U., Herrmann, A., Loges, R., Dittert, K., Taube, F., 2011. Recovery of mineral fertilizer N and slurry N in continuous silage maize using the 15N and difference methods. Nutr. Cycl. Agroecosyst. 89, 269–280. Nishida, M., Tsuchiya, K., Yamamuro, S., 2004. Fate of N and relative efficiency of 15Nlabeled organic materials applied to transplanted rice in Northern Kyushu region of Japan. Soil Sci. Plant Nutr. 50, 225–232. Nyiraneza, J., Chantigny, M.H., N’Dayegamiye, A., Lave`rdiere, M.R., 2010. Long-term manure application and forages reduce nitrogen fertilizer requirements of silage corncereal cropping systems. Agron. J. 102, 1244–1251. Olesen, J.E., Sorensen, P., Thomsen, I.K., Eriksen, J., Thomsen, A.G., Berntsen, J., 2004. Integrated nitrogen input systems in Denmark. In: Agriculture and the Nitrogen Cycle. 65, Scope, pp. 129–140. Pakro, N., Dillon, P., 1995. Preferential flow, nitrogen transformations and 15N balance under urine-affected areas of irrigated and non-irrigated clover-based pastures. J. Contam. Hydrol. 20, 329–347. Park, S.H., Lee, B.R., Jung, K.H., Kim, T.H., 2018. Acidification of pig slurry effects on ammonia and nitrous oxide emissions, nitrate leaching, and perennial ryegrass regrowth as estimated by 15N-urea flux. Asian Australas. J. Anim. Sci. 31, 457–466. Paul, J.W., Beauchamp, E.G., 1995. Availability of manure slurry ammonium for corn using 15 N-labeled (NH4)2SO4. Can. J. Soil Sci. 75, 35–42. Petersen, J., 2005. Competition between weeds and spring wheat for 15N-labeled nitrogen applied in pig slurry. Weed Res. 45, 103–113. Petersen, J., 2006. Crop 15N recovery course affected by spatial distribution of animal slurries in soils. Nutr. Cycl. Agroecosyst. 75, 15–27. Pomares-Garcia, F., Pratt, P.F., 1978. Recovery of 15N-labeled fertilizer from manured and sludge-amended soils. Soil Sci. Soc. Am. J. 42, 717–720.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
59
Powell, J.M., Wu, Z., 1999. Nitrogen-15 labeling of dairy feces and urine for nutrient cycling studies. Agron. J. 91, 814–818. Powell, J.M., Wu, Z., Kelling, K., Cusick, P., Mun˜oz, G., 2004. Differential nitrogen-15 labeling of dairy manure components for nitrogen cycling studies. Agron. J. 96, 433–441. Powell, J.M., Kelling, K.A., Mun˜oz, G.R., Cusick, P.R., 2005. Evaluation of dairy manure nitrogen-15 enrichment methods on short-term crop and soil nitrogen budgets. Agron. J. 97, 333–337. Powell, J.M., Barros, T., Danes, M., Aguerre, M., Wattiaux, M., Reed, K., 2017. Nitrogen use efficiencies to grow, feed, and recycle manure from the major diet components fed to dairy cows in the USA. Agric. Ecosyst. Environ. 239, 274–282. Primo, D.C., Menezes, R.S.C., Sampaio, E.V.S.B., Garrido, M.S., Junior, J.C.B., Souza, C.S., 2014. Recovery of N applied as 15N-manure or 15N-gliricidia biomass by maize, cotton and cowpea. Nutr. Cycl. Agroecosyst. 100, 205–214. Senbayram, M., Chen, R., M€ uhling, K.H., Dittert, K., 2009. Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers. Rapid Commun. Mass Spectrom. 23, 2489–2498. Shand, C.A., Williams, B.L., Smith, S., Young, M.E., 2000. Temporal changes in C, P and N concentrations in soil solution following application of synthetic sheep urine to a soil under grass. Plant Soil 222, 1–13. Shepherd, M., Menneer, J., Ledgard, S., Sarathchandra, U., 2010. Application of carbon additives to reduce nitrogen leaching from cattle urine patches on pasture. N. Z. J. Agric. Res. 53, 263–280. Silva, R.G., Cameron, K.C., Di, H.J., Smith, N.P., Buchan, D.G., 2000. Effect of macropore flow on the transport of surface-applied cow urine through a soil profile. Aust. J. Soil Res. 38, 13–24. Silva, R.G., Cameron, K.C., Di, H.J., Jorgensen, E.E., 2005. A lysimeter study to investigate the effect of dairy effluent and urea on cattle urine N losses, plant uptake and soil retention. Water Air Soil Pollut. 164, 57–78. Smith, C.J., Chalk, P.M., 2018. The residual value of fertiliser N in crop sequences: an appraisal of 60 years of research using 15N tracer. Field Crop Res. 217, 66–74. Sommer, S.G., Jensen, E.S., Schjørring, J.K., 1993. Leaf absorption of atmospheric ammonia emitted from pig slurry applied beneath the canopy of winter wheat. Acta Agric. Scand. B. Soil Plant Sci. 43, 21–24. Sørensen, P., 2004. Immobilization, remineralization and residual effects in subsequent crops of dairy cattle slurry nitrogen compared to mineral fertilizer nitrogen. Plant Soil 267, 285–296. Sørensen, P., Amato, M., 2002. Remineralization and residual effects of N after application of pig slurry to soil. Eur. J. Agron. 16, 81–95. Sørensen, P., Jensen, E.S., 1995a. Mineralization of carbon and nitrogen from fresh and anaerobically stored sheep manure in soils of different texture. Biol. Fertil. Soils 19, 29–35. Sørensen, P., Jensen, E.S., 1995b. Mineralization-immobilization and plant uptake of nitrogen as influenced by the spatial distribution of cattle slurry in soils of different texture. Plant Soil 173, 283–291. Sørensen, P., Jensen, E.S., 1996. The fate of fresh and stored 15N-labeled sheep urine and urea applied to a sandy and a sandy loam soil using different application strategies. Plant Soil 183, 213–220. Sørensen, P., Jensen, E.S., 1998. The use of 15N labelling to study the turnover and utilization of ruminant manure N. Biol. Fertil. Soils 28, 56–63. Sørensen, P., Thomsen, I.K., 2005. Production of nitrogen-15-labeled pig manure for nitrogen cycling studies. Soil Sci. Soc. Am. J. 69, 1639–1643. Sørensen, P., Thomsen, I.K., 2005b. Separation of pig slurry and plant utilization and loss of nitrogen-15-labeled slurry nitrogen. Soil Sci. Soc. Am. J. 69, 1644–1651.
ARTICLE IN PRESS 60
Phillip M. Chalk et al.
Sørensen, P., Jensen, E.S., Nielsen, N.E., 1994a. Labelling of animal manure nitrogen with 15 N. Plant Soil 162, 31–37. Sørensen, P., Jensen, E.S., Nielsen, N.E., 1994b. The fate of 15N-labeled organic nitrogen in sheep manure applied to soils of different texture under field conditions. Plant Soil 162, 39–47. Stevens, R.J., Gracey, H.I., Laughlin, R.J., Logan, H.J., 1986. The influence of two soil nitrogen levels on the utilization of 15N-labeled ammonium nitrate by ryegrass. J. Sci. Food Agric. 37, 454–460. Stevens, R.J., Laughlin, R.J., Logan, H.J., 1987. Interactions between cow slurry and 15Nlabeled calcium nitrate as fertilizers for ryegrass production. J. Sci. Food Agric. 41, 309–314. Sun, J., Bai, M., Shen, J., Griffith, D.W.T., Denmead, O.T., Hill, J., Lam, S.K., Mosier, A.R., Chen, D., 2016. Effects of lignite application on ammonia and nitrous oxide emissions from cattle pens. Sci. Total Environ. 565, 148–154. Taghizadeh-Toosi, A., Clough, T.J., Condron, L.M., Sherlock, R.R., Anderson, C.R., Craigie, R.A., 2011. Biochar incorporation into pasture soil suppresses in situ nitrous oxide emissions from ruminant urine patches. J. Environ. Qual. 40, 468–476. Taghizadeh-Toosi, A., Clough, T.J., Sherlock, R.R., Condron, L.M., 2012. A wood based low-temperature biochar captures NH3-N generated from ruminant urine-N, retaining its bioavailability. Plant Soil 353, 73–84. Tagoe, S.O., Horiuchi, T., Matsui, T., 2008. Effect of carbonized and dried chicken manures on the growth, yield, and N content of soybean. Plant Soil 306, 211–220. Thompson, R.B., Fillery, I.R.P., 1998. Fate of urea nitrogen in sheep urine applied to soil at different times of the year in the pasture-wheat rotation in South Western Australia. Crop Pasture Sci. 49, 495–510. Thomsen, I.K., 2000. C and N transformations in 15N cross-labeled solid ruminant manure during anaerobic and aerobic storage. Bioresour. Technol. 72, 267–274. Thomsen, I.K., 2001. Recovery of nitrogen from composted and anaerobically stored manure labeled with 15N. Eur. J. Agron. 15, 31–41. Thomsen, I.K., 2004. Nitrogen use efficiency of 15N-labeled poultry manure. Soil Sci. Soc. Am. J. 68, 538–544. Thomsen, I.K., 2005. Crop N utilization and leaching losses as affected by time and method of application of farmyard manure. Eur. J. Agron. 22, 1–9. Thomsen, I.K., Kjellerup, V., 1997. Yields and N uptake of barley and ryegrass from soils with added animal manure differing in straw and urine content. Eur. J. Agron. 7, 285–292. Thomsen, I.K., Kjellerup, V., Jensen, B., 1997. Crop uptake and leaching of 15N applied in ruminant slurry with selectively labeled feces and urine fractions. Plant Soil 197, 233–239. Thomsen, I.K., Schjønning, P., Christensen, B.T., 2003. Mineralization of 15N-labeled sheep manure in soils of different texture and water contents. Biol. Fertil. Soils 37, 295–301. Trehan, S.P., 1994. Immobilization of 15NH4 by cattle slurry decomposing in soil. Soil Biol. Biochem. 26, 743–745. Trehan, S.P., Wild, A., 1993. Effects of an organic manure on the transformations of ammomium nitrogen in planted and unplanted soil. Plant Soil 151, 287–294. Uchida, Y., Clough, T.J., Kelliher, F.M., Hunt, J.E., Sherlock, R.R., 2011. Effects of bovine urine, plants and temperature on N2O and CO2 emissions from a sub-tropical soil. Plant Soil 345, 171–186. Uenosono, S., Takahashi, S., Nagatomo, M., Yamamuro, S., 2002. Labeling of poultry manure with 15N. Soil Sci. Plant Nutr. 48, 9–13. Vallis, I., Gardner, C.J., 1984. Short-term nitrogen balance in urine-treated areas of pasture on a yellow earth in the subhumid tropics of Queensland. Anim. Prod. Sci. 24, 522–528.
ARTICLE IN PRESS Tracing the dynamics of animal excreta N
61
Vallis, I., Peake, D.C.I., Jones, R.K., McCown, R.L., 1985. Fate of urea nitrogen from cattle urine in a pasture-crop sequence in a seasonally dry tropical environment. Crop Pasture Sci. 36, 809–817. Wachendorf, C., Joergensen, R.G., 2011. Mid-term tracing of 15N derived from urine and dung in soil microbial biomass. Biol. Fertil. Soils 47, 147–155. Wachendorf, C., Taube, F., Wachendorf, M., 2005. Nitrogen leaching from 15N labeled cow urine and dung applied to grassland on a sandy soil. Nutr. Cycl. Agroecosyst. 73, 89–100. Wachendorf, C., Lampe, C., Taube, F., Dittert, K., 2008. Nitrous oxide emissions and dynamics of soil nitrogen under 15N-labeled cow urine and dung patches on a sandy grassland soil. J. Plant Nutr. Soil Sci. 171, 171–180. Welten, B.G., Ledgard, S.F., Schipper, L.A., Judge, A.A., 2013. Effect of amending cattle urine with dicyandiamide on soil nitrogen dynamics and leaching of urinary-nitrogen. Agric. Ecosyst. Environ. 167, 12–22. Whitehead, D.C., Bristow, A.W., 1990. Transformations of nitrogen following the application of 15N-labeled cattle urine to an established grass sward. J. Appl. Ecol. 27, 667–678. Williams, P.H., Haynes, R.J., 1994. Comparison of initial wetting pattern, nutrient concentrations in soil solution and the fate of 15N-labeled urine in sheep and cattle urine patch areas of pasture soil. Plant Soil 162, 49–59. Williams, P.H., Haynes, R.J., 2000. Transformations and plant uptake of urine N and S in long and short-term pastures. Nutr. Cycl. Agroecosyst. 56, 109–116. Williams, B.L., Dawson, L.A., Grayston, S.J., Shand, C.A., 2003. Impact of defoliation on the distribution of 15N-labeled synthetic sheep urine between shoots and roots of Agrostis capillaris and soil N pools. Plant Soil 251, 269–278. Woods, R.R., Cameron, K.C., Edwards, G.R., Di, H.J., Clough, T.J., 2017. 15N recoveries from ruminant urine patches on three forage types. Plant Soil 417, 453–465. Wu, C.-L., Shen, Q.-R., Mao, J.-D., Xu, Y.-C., 2010. Fate of 15N after combined application of rabbit manure and inorganic N fertilizers in a rice–wheat rotation system. Biol. Fertil. Soils 46, 127–137.