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Infiltration of Slurry and Ammonia Volatilisation
ARTICLE IN PRESS Biosystems Engineering (2004) 88 (3), 359–367 doi:10.1016/j.biosystemseng.2004.03.008 SE}Structures and Environment
Available online at www.sciencedirect.com
Infiltration of Slurry and Ammonia Volatilisation S.G. Sommer; M.N. Hansen; H.T. Søgaard Department of Agricultural Engineering, Danish Institute of Agricultural Sciences, Research Centre Bygholm, P.O. Box 536, DK-8700 Horsens, Denmark; E-mail of corresponding author: [email protected] (Received 21 July 2003; accepted in revised form 10 March 2004; published online 15 June 2004)
Volatilisation of ammonia (NH3) from slurry applied in the field reduces the fertiliser value of the slurry and is liable to cause a considerable uncertainty in the nitrogen (N) fertiliser efficiency. A better understanding of slurry–soil interactions is needed in order to develop reliable decision support systems for the use of animal slurry as manure. In this field study, infiltration of slurry in the soil was estimated by measuring chloride (Cl) and ammonium (TAN ¼ NH3+NH+ 4 ) concentrations at different depths from 05 to 75 cm below the soil surface. The NH3 volatilisation was measured using micrometeorological methods and was related to infiltration. Slurry applied to sandy or clay-loam soils infiltrated to 2–25 cm. Ammonium and Cl infiltration could not be related to slurry, soil and climatic variables because the measured infiltration rates were spatially variable. In spite of this spatial variability, the infiltration parameters of TAN explained a large proportion of the variation in NH3 volatilisation. Therefore, reliable models that currently include, wind, soil surface temperature, TAN and pH of applied slurry as parameters for predicting NH3 volatilisation may also benefit by including parameters for TAN infiltration. Models calculations using soil surface TAN concentration, pH and temperature during the volatilisation event are more precise than calculations using air temperature during the study and TAN concentration and pH in slurry at time of application. # 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd
1. Introduction The nitrogen (N) fertiliser efficiency of animal slurry is variable due to volatilisation of ammonia (NH3), uneven spreading of slurry in the field and a low availability of the manure nitrogen (Sommer et al., 2003). The difficulty in assessing the fertiliser value of the manure can lead to a tendency of over-applying N to ensure a good crop growth (Grant et al., 1993). Furthermore, manure from livestock production is considered to be a major source of atmospheric NH3 (Buijsman et al., 1987), which, when deposited, can cause undesirable changes in natural ecosystems (Jenkinson, 2001). To improve plant uptake and reduce N loss to the environment, techniques have been developed for the purpose of improving the fertiliser efficiency of slurry by reducing NH3 volatilisation and improving spreading evenness of slurry in the field. Of these techniques, injection and trail hose application of slurry both seem to hold a potential for reducing NH3 volatilisation and 1537-5110/$30.00
for spreading slurry homogeneously in the field, as compared to the traditional spreading techniques using a splash plate (Sommer et al., 2001). A substantial part of the slurry produced in Denmark is applied to crops during the spring (Hutchings et al., 2001), when the trail hose application technique has a low efficiency in reducing NH3 volatilisation, because crops are low or absent and are not providing shade or shelter for the wind (Hansen et al., 2003). Alternatively, a direct injection technique can be used, but this technique is more labour-intensive and energy-demanding than trail hose application of slurry (Huijsmans et al., 1998; Hansen et al., 2003) and may damage winter-crops (Prins & Snijders, 1987; Long & Gracey, 1990). Furthermore, the effectiveness of injection can be low if the soil is moist and compacted, and the slit remains open (Klarenbeek & Bruins, 1991; Phillips et al., 1991). Efficiency of the trail hose and direct injection may be improved by enhancing the infiltration of slurry liquid into the soil, because increased infiltration will reduce 359
# 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd
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Notation a0 a1 a2 a3 a4
A Ach Azinst b0 b1 b2 b3 b4
C Ceq Ca Cch Cz
Clrel
CL CL
CL
intercept parameter in NH3 emission model model parameter relating NH3 emission to air temperature model parameter relating NH3 emission to wind speed model parameter relating NH3 emission to TANrel model parameter relating NH3 emission to equilibrium NH3 calculated using TAN and pH at the time of slurry application and air temperature at time tp exposed area of the filter used in the JTI technique, m2 area of emitting surface covered by the JTI chamber, m2 effective cross-sectional area of the Leuning sampler, m2 intercept parameter in NH3 emission model model parameter relating NH3 emission to air temperature model parameter relating NH3 emission to wind speed model parameter relating NH3 emission to TANrel model parameter relating NH3 emission to the equilibrium NH3 concentration in the slurry at the soil surface at time tp concentration of NH3 in the air, mg m3 equilibrium concentration of NH3 in the air at the emitting surface, mg [NH3-N] m3 ammonia concentration in the air above the emitting surface, mg [NH3-N] m3 ammonia concentration of air inside the JTI chamber, mg [NH3-N] m3 concentration of Cl1 and total ammonaical nitrogen (TAN) in soil liquid in soil layers Z, g l1 amount of Cl1 in the 0–05 cm surface layer relative to the amount in the entire profile (0– 75 cm) equilibrium concentration of NH3 in the soil slurry mixture, g [N] l1 equilibrium concentration of NH3 in the slurry calculated using TAN and pH in slurry at time of application and air temperature during the experiment, g [N] l1 equilibrium concentration of NH3 in the soil slurry mixture calculated using TAN, pH and
D F Fch Fr ðts Þ Hinst Ka Kch LR LLBL M Q Sa T
tp Ta Ts TANi TANrel
u V X Y Z Zinf ZINST w
temperature in the surface layer of slurry during the experiment, g [N] l1 diffusion coefficient for NH3 in air, m2 s1 ammonia volatilisation rate, mg [NH3-N] m3 s1 flux from the JTI chamber, mg [NH3-N] m3 s1 NH3 emission at time ts relative to applied TAN height at which atmospheric NH3 concentration is measured in the ZINST technique, m mass transfer coefficient for NH3, s1 mass transfer coefficient for NH3 inside the JTI chamber, s1 distance between the Teflon membrane filter and NH3 absorbing filter, m laminar boundary layer above the top of NH3 absorbing filter, m mass of NH3 collected by the Leuning sampler, g [NH3-N] air flow through the JTI chamber, m3 s1 application rate of slurry, t [slurry] ha1 exposure time of the PDS absorbers used to measure NH3 concentration or exposure time of the passive flux samplers used to measure the horizontal flux of NH3, h time from slurry application, h air temperature, 8C soil slurry surface temperature, 8C concentration of TAN in the slurry at time of application, kg [N] t1 amount of TAN in the 0–05 cm surface layer relative to the amount in the entire profile 0– 75 cm wind speed at a single height above the ground, m s1 volume of soil water in the layer Z1 to Z8, l amount of NH3 collected by the PDS-C type, mg [NH3-N] amount of NH3 collected by the PDS-L type, mg [NH3-N] depth of the soil layer, cm average amount weighted depth of infiltration of chloride Cl1 and TAN, cm unit flux uw/F ratio used by the ZINST technique atmospheric NH3 concentration at the Hinst height, mg [NH3-N] m3
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NH3 volatilisation (Sommer & Olesen, 1991; Sommer & Ersbøll, 1994; Thompson et al., 1990). A high slurry and dry matter content (DM) of slurry may reduce infiltration of slurry, therefore, NH3 volatilisation is reduced by reducing viscosity and DM by separation, fermentation in a biogas reactor or diluting the slurry (Sommer et al., 2003). In this paper, six field experiments were conducted to relate infiltration as affected by category of animal producing the slurry, slurry treatment and soil type. Ammonia volatilisation was related to infiltration of slurry into the soil, slurry characteristics and soil condition. The main objective was to contribute to the development of reliable decision support systems for slurry application, with the purpose of reducing NH3 volatilisation.
2. Materials and methods 2.1. Study site Ammonia volatilisation from slurry applied with a trail hose to six different soils was studied in six experiments at two sites in Denmark; a farm in the western part of Jutland and at Research Centre Bygholm in the eastern part of Jutland (Table 1). The study sites were either fallow, or spring barley, or grass fields. The cereals were drilled in rows 12 cm apart. The soil in western Jutland is classified as a sandy soil and the soil at Research Centre Bygholm as a clay loam. To provide an option for comparing the effect of different soil textures under similar climate conditions, a 20 cm layer of sandy soil was laid out in a 20 m by 20 m square in the field at Research Centre Bygholm in the October 2000 and April 2001 experiments. In arable fields the top soil is cultivated several times a year, therefore, a 20 cm
layer of ‘new’ top soil will represent the surface of a field when measuring infiltration of slurry into the soil within one week after slurry application i.e. the period with significant volatilisation of NH3. In the six experiments, slurry was applied at rates from 300 to 377 m3 ha1. The slurry was spread with a trail hose spreader equipped with 40 trail hoses mounted 30 cm apart on a 12 m spreading bar. The bar was mounted 1 m above the soil surface but the trail hoses allowed the slurry to be placed exclusively on the soil between the rows of plants. In the experiments started on 10 October 2000, 3 April 2001 and 24 April 2001, slurry was applied in 20 m by 20 m parcels covering the sandy soil plot and the sandy loam Bygholm soil. In the experiments started on 30 May 2000, 15 May 2001 and 7 May 2002, slurry was applied to square experimental plots (36 m by 36 m). Application rates and characteristics of the pig slurries used in the study are presented in Tables 2 and 3. Meteorological data (Table 4) were obtained from the meteorological station at Research Centre Bygholm, located less than 500 m from the experimental sites, and the meteorological station at approximately 20 km from the farm in western Jutland. Data used in this study were 10 min values of air temperature (2 m), soil temperature (01 m), wind speed (10 m), incident solar radiation (20 m) and precipitation (15 m). During the experiments from May 2000 to April 2001, soil surface temperature was measured with a standard thermocouple temperature sensor pushed into the upper 05 cm of the soil surface. 2.2. Soil analysis In each plot two soil cores from 0–75 cm depths were collected with steel cylinders (0097 m in diameter by
Table 1 Characteristics of soil and crop to which slurry was applied in this study, a plow layer was provided by laying out a 20 cm layer of sandy soil in the experiment with application date 10th October 2000, 3rd and 24th of April 2001 Application date
30 May 2000 10 Oct 2000, 3 April 2001 and 24 April 2001 10 Oct 2000 3 April 2001 and 24 April 2001 15 May 2001 7 May 2002 ND, not determined. OM, organic matter.
Clay, 52 mm % w/w
Loam, 2–20 mm % w/w
Loam, 20–63 mm % w/w
Sand, 63–200 mm % w/w
Sand, % w/w
OM % w/w
C % w/w
Crop
13 111
15 135
136 103
274 334
269 285
38 31
ND 18
Grass 5 cm None
75 42
12 38
125 33
393 164
257 695
3 28
18 16
None None
235 103
24 122
135 127
1585 281
751 334
30 34
173 198
Spring Barley 7 cm Spring barley 5 cm
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Table 2 Characteristics of the slurry applied to fields in the experiments Application date
30 10 3 24 15 15 15 15 15 7 7 7
Animal
May 2000 Oct 2000 April 2001 April 2001 May 2001 May 2001 May 2001 May 2001 May 2001 May 2002 May 2002 May 2002
Treatment
Cattle Cattle Cattle Pig Pig Pig Pig Pig Pig Pig Pig Pig
Manure composition
No No No No No Diluted Digested Digested, separated Digested, separated, diluted No Digested Digested, separated
pH
TAN, g kg1
Cl, g kg1
Total-N, g kg1
DM, %
71 74 71 ND ND 69 81 85 84 736 809 827
160 110 131 072 072 19 44 51 25 307 37 36
077 077 123 041 041 ND ND ND ND ND ND ND
352 370 251 178 178 24 45 54 26 43 51 48
863 501 955 138 138 160 280 298 13 328 323 215
ND, not determined. DM, dry matter content of slurry.
Table 3 Characteristics of soil water, application rate and width of slurry band Application date 30 10 3 24 10 3 24 15 7
Soil water, vol %
Application rate, t ha1
253 307 215 193 272 169 129 112–226 ND
30 30 336 30 30 336 300 377 266
May 2000 Oct 2000 April 2001 April 2001 Oct 2000* April 2001* April 2001* May 2001 May 2002
Width of slurry band, cm 125 74 74 30 74 74 300 10 ND
In the experiment starting the 15th of May 2001 the plot to which slurry was applied in the morning was dry, at later application of slurry rain during increased soil surface water content. ND, not determined. * A plough layer was provided by laying out a 20 cm layer of sandy soil in the experiment with application date 10th October 2000, 3rd and 24th April 2001, therefore two different soils were included in the experiments.
Table 4 Mean air and soil temperature, solar radiation and wind, and cumulated rain during the experimental periods Measuring period Start
End
30 10 3 24 15 7
13 June 2000 16 Oct 2000 9 April 2001 20 April 2001 22 May 2001 14 May 2002
May 2000 Oct 2000 April 2001 April 2001 May 2001 May 2002
ND, Not determined.
Air temperature, 8C
Soil temperature,8C
113 98 77 91 1129 126
111 89 58 71 1250 120
Radiation, W m2 ND 7232 11 893 19 633 6609 ND
Wind speed, m s1
Rain, mm
45 77 61 42 278 52
205 7 19,4 27,2 42 04
ARTICLE IN PRESS VOLATILISATION OF AMMONIA FROM SLURRY
008 m in height) that were pushed into the soil in the middle of the slurry bands. The soil columns were sliced into segments (0–05, 05–1, 1–15, 15–2, 2–25, 25–35, 35–5, 5–75 cm) by carefully pushing up the soil with a piston and cutting of the excess soil extending over the top of the core. Soil-water content was determined by drying a sub-sample from each slice at 1058C for 24 h. Ammonium (TAN ¼ NH3+ NH+ 4 ) content was extracted with 10 M potassium chloride for 05 h and Cl with deionised water for 05 h. The ammonium and Cl contents were determined colorimetrically using a spectrophotometer (Shimadzu UV-120-01, Japan) for TAN and a Merck-Spectroquant NOVA 60 (Darmstad, Germany) for Cl determination. At soil sampling soil slurry surface pH was measured with a flat-headed pH electrode and a portable pH-meter (Radiometer, PHM80 portable pH meter, Copenhagen, DK). In each experiment soil were sampled 3 h after application of slurry to the plot and in experiments with slurry application the 30 May 2000, 10 October 2000, 3 April 2001 and 24 April 2001 soil was sampled 1, 3, 7, 24, 48, 73, 145 h after slurry application. 2.3. Ammonia volatilisation In the experiments started on 10 October 2000, 3 April 2001 and 24 April 2001, NH3 volatilisation was determined with the JTI method (Misselbrook & Hansen 2001). The JTI method uses the micrometeorological law of resistance to determine the horizontal flux of NH3 (F in mg [NH3-N] m3 s1) from the equilibrium concentration of NH3 in the air at the emitting surface Ceq in mg [NH3-N] m3, the NH3 concentration in the air above the emitting surface (Ca in mg [NH3-N] m3) and the mass transfer coefficient for NH3 (Ka in s1) F ¼ ðCeq Ca Þ Ka
ð1Þ
Passive diffusion samplers (PDS) are used to measure NH3 concentration in the air. Two types of PDS are used which differ in the length of the diffusion path. For the L-type, the NH3 absorbing filter is placed at the top, directly exposed to the ambient air. The C-type has the NH3 absorbing filter placed 10 mm below a Teflon membrane filter. The amount of NH3 collected by the PDS-C type (X in mg) and PDS-L type (Y in mg) is given by A X ¼ DCt ð2Þ LR LLBL and Y ¼ DCt
A LLBL
ð3Þ
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respectively, where D is the diffusion coefficient for NH3 in air in m2 s1, C the concentration of NH3 in the air in mg m3, t the sampling time for the PDS in s, A the exposed area of the filter in m2, LR the distance in m between the Teflon membrane filter and the NH3 absorbing filter for PDS-C type and LLBL the laminar boundary layer in m above the top of the PDS. By combining Eqns (2) and (3), an expression for LLBL can be derived: XLR ð4Þ LLBL ¼ ðY X Þ The mass transfer coefficient can then be derived from the relationship D Ka ¼ ð5Þ LLBL By using the two types of PDS close to the surface of a treated plot, both the concentration of NH3 in the air just above the emitting surface and the mass transfer coefficient can be determined from Eqns (2)–(5). The other parameter required in Eqn (1), Ceq, is determined by use of a ventilated chamber. The chamber is ventilated by a fan via small inlet and outlet openings at one end, to ensure that condensation does not form on the internal walls. Inlet air to the chamber is assumed to have an NH3 concentration Ca, as measured by the PDS outside the chamber. The NH3 flux from the area (Fch in mg [NH3-N] m3 s1) covered by the chamber can be calculated according to Eqn (1) as Fch ¼ Ceq Cch Kch ð6Þ where Cch is the NH3 concentration of air inside the chamber in mg [NH3-N] m3 and Kch the mass transfer coefficient for NH3 inside the chamber in s1 (which should be constant for a given flow rate and surface conditions). The flux Fch in mg from the chamber can also be calculated by mass balance ðCch Ca ÞQ Fch ¼ ð7Þ Ach where Q is the air flow rate through the chamber in m3 s1 and Ach the area of emitting surface covered by the chamber in m2. Combining Eqns (6) and (7) gives an expression for the equilibrium concentration at the emitting surface Q=Ach Q=Ach Ceq ¼ Cch 1 þ Ca ð8Þ Kch Kch This can then be used in Eqn (1) together with the determined values for Ca and Ka, to derive the flux from the treated area for the measurement period. More information about the method is presented by Svensson and Ferm (1993) and Svensson (1994). Three chambers were used to estimate the emission from each plot and
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the emission was determined for the time intervals: 0–1, 1–3, 3–7, 7–24, 24–48, 48–144 h. In the experiments started on 30 May 2000, 15 May 2001 and 7 May 2002, NH3 volatilisation was measured with the micrometeorological mass balance method described by Wilson et al. (1982). The volatilisation can be inferred from measurements of increase in atmospheric NH3 concentration in the air parcels passing the experimental plot w in mg [NH3-N] m3 and wind speed u in m s1 at a single height Hinst in m above the ground uw F¼ ð9Þ ZINST The term ZINST is the unit flux uw/F ratio, which is given by Wilson et al. (1982). The horizontal flux (uw) was measured using passive Leuning samplers (Leuning et al., 1985) mounted at the Hinst height 09 m above the soil surface, on masts placed at the upwind edge and at the centre of the plot (radius 18 m). According to Leuning et al. (1985), uw is derived from M ð10Þ uw ¼ Azinst t where M is the mass of NH3-N in g collected by coating the interior of the Leuning sampler with oxalic acid during sampling period t in s and Azinst is the effective cross-sectional area of the sampler in m2 determined in wind-tunnel calibrations. After exposure, the coating was dissolved in 0040 l of deionised water and the NH4-N content in g l1 determined by the indophenol blue colorimetric method using a spectrophotometer (Shimadzu UV-120-01, Japan). Two space shuttles were used to estimate the emission from each plot and the emission was determined for the time intervals: 0–2, 2–6, 6–23, 23–50, 50–71, 71–98, 98–166 h.
3. Results and discussion Figure 1 shows that the TAN and Cl concentrations in the soil are elevated due to infiltration of slurry liquid to a depth of 2–25 cm below the soil surface underneath a slurry band. The fraction of TAN near the soil surface is higher than the fraction of Cl , and in Fig. 2 the infiltration of TAN is related to the infiltration of Cl (probability P5001), showing that a larger fraction of Cl is infiltrating to greater depth than is the case for TAN, indicating that NH+ 4 has been absorbed in the surface layers by soil colloids. Ammonium is retained by soil cation exchange capacity (Fleisher et al., 1987) and therefore transport of NH+ 4 infiltration lags behind the waterfront into the soil. On the other hand, the negative ion Cl is not retained by absorption to the negatively charged soil colloids and is therefore transported convectively with soil water. In a laboratory study, applying 3 l m2 slurry to soils packed in columns; the maximum infiltration depth of the conservative ion bromide (Br) was 175 cm (Sommer & Jacobsen, 1999). Statistical analyses did not indicate significant relationships between infiltration (of Cl and TAN) and slurry composition, soil and climate. One reason for this is that measurements of infiltration in the field are highly variable due to heterogeneous soil surfaces with small pits in which slurry forms ponds; furthermore, uneven spreading of slurry in field experiments contributes to spatially uneven volumes of slurry applied in the plots (Langenakens et al., 2001). In the present study the variations in slurry applied per site are larger than the differences in infiltration due to different soils and slurries. Two statistical models were applied for analysis of the relationship between ammonia volatilisation and other
2.0 1.5 1.0
3
2
1
0.5 0.0
(a)
4
TAN, g[N] l −1
Chloride, g [Cl] l −1
2.5
0
1
2 Depth, cm
3
0 0
4 (b)
1
2
3
4
Depth, cm
Fig. 1. (a) Concentration profile of chloride and (b) total ammoniacal nitrogen (TAN) 3 h after application of pig slurry in May 2002; pre- treatment of the pig slurries were: - - * - - , untreated; }* –, anaerobic digested; – . – , anaerobic digested and separated
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variables (see Appendix A for mathematical equations). Model 1 demands knowledge of TAN and pH in the slurry applied, the amount of TAN in the 0–05 cm surface layer relative to that in full profile of 0–75 cm, denoted by TANrel, after application of slurry, and air temperature and wind speed during the volatilisation
TAN, average depth cm
2.5 2.0 1.5 1.0 0.5 0.0 0.0
0.5
1.0
1.5
2.0
2.5
3.0
Chloride, average depth cm Fig. 2. Infiltration of total ammoniacal nitrogen (TAN) as a function F of chloride infiltration expressed as weighted average depth of infiltration [Eqn (4)]; coefficient of determination R2 ¼ 029, F ¼ 034x þ 058
event, as NH3 volatilisation was shown to be significantly (P501, Table 5) related to these variables. In Model 1 [Eqn (A4)] the air temperature Ta in 8C for the time from slurry application tp in h is represented explicitly through the factor a1Ta ðtP Þ and implicitly C ðt Þ through the factor a4 L P , since the estimate of the equilibrium NH3 concentration CL ðtP Þ in g [N] l1 is a function of air temperature. Equilibrium between slurry NH3 and atmospheric NH3 are not included in the model; the effect of this process on NH3 volatilisation can therefore be expressed as an effect of air temperature, because temperature is included when calculating the equilibrium between liquid and atmospheric NH3 (Henry’s constant, G!enermont & Cellier, 1997). In Model 2 [Appendix A, Eqn (A5)], NH3 volatilisation is significantly (P501) related to soil temperature, wind speed, relative TAN concentration and NH3 concentrations (Table 5). As in Model 1, temperature has a significant effect on NH3 volatilisation due to its impact on the equilibrium between NH3 in solution and atmospheric NH3 (G!enermont & Cellier, 1997). Model 2 (the coefficient of determination R2 ¼ 077), which includes NH3 concentration calculated from Eqn (A3) using TAN, pH and temperature in the slurry soil mixture, is more precise than Model 1 (R2 ¼ 063), which is based on bulk concentrations of TAN and pH in the
Table 5 Results of the statistical analysis; Model 1 [Eqn (7)] is based on 76 observations of ammonia emission and the value for the coefficient of determination R2 is 0.63; Model 2 [Eqn (8)] is based on only 51 observations of ammonia emission and the value for R2 is 0.77; the number of observations used for Model 2 is lower than the number of observations used for Model 1 due to missing estimates of C,L**; variables significant at probability P50.15 are included in the models Model 1
2
Experimental factor
Parameter estimate
None Air temperature Ta
43–1348C
a0 ¼ 93 107 a1 ¼ 137
Wind speed u
20–107 m s1
a2 ¼ 154
Relative ammonium conc. in slurry/soil surface TANrel Estimated NH3 concentrationa C*L
15–84%
a3 ¼ 107
0002–0320 g l1
a4 ¼ 115 106
43–1078C
b0 ¼ 75 107 b1 ¼ 122
33–107 m s1
b2 ¼ 187
27–83%
b3 ¼ 105
0002–0028 g l1
b4 ¼ 117 1030
None Temperature of soil surface/ slurry Ts Wind speed u Relative ammonium conc. in slurry/soil surface TANrel Estimated NH3 concentrationb C** ,L a
Range
Effect on NH3 emission +37% per 8C increase in air temp +54% per m s1 increase in wind speed +7% per % increase in TANrel conc. +15% per 0.01 g/l increase in NH3 conc. +22% per 8C increase in air temperature +87% per m s1 increase in wind speed +5% per % increase in TANrel conc. +100% per 001 g/l increase in NH3 conc.
95% confidence interval +18 60% +38% 73% +5 9% +7% 23%
5 57% +63% 114% +3 8% +2% 192%
The CL concentration was estimated from air temperature, initial TAN concentration and pH in the slurry using Eqn (A3). The CL concentration was estimated from TAN, pH and temperature in the surface slurry/soil layer at time t of application using Eqn (A3). b
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applied slurry and air temperature. This is to be expected because NH3 equilibrium is more precisely estimated by using the composition and surface temperature of slurry and soil mixture, as TAN and pH in slurry on the soil will be different from the initial composition of the slurry due to volatilisation of NH3 and changes in pH (G!enermont & Cellier, 1997; Sommer & Olesen, 2000). In decision support systems, initial TAN concentrations and pH of the slurry, soil surface temperature, wind and a submodel for infiltration can be used to predict NH3 volatilisation. This study indicated that models for predicting pH of the surface of slurry and soil mixture can improve the models significantly. The results suggest that relating NH3 volatilisation to the proportion of TAN in the topsoil/slurry layer can contribute to modelling the effect of TAN infiltration. In studies of NH3 volatilisation it can be appropriate to assess infiltration by measuring TAN in the surface layer and relating it either to the amount of TAN in the soil or to the amount of TAN applied in slurry. Thereby, infiltration can be characterised with two analyses per soil sampling, i.e. soil and slurry surface sample and a sample from 0 to 5 cm.
4. Conclusions Infiltration of chloride (Cl1) from slurry applied to sandy or sandy loam soils was spatially very variable. The Cl1 infiltration was between 2 and 3 cm in this field study and Cl1 was infiltrating to greater depths than ammonium. Ammonium concentration in soil samples and infiltration of ammonium explained a significant part of the variation in NH3 volatilisation. Ammonia volatilisation was also related to wind, soil surface temperature and air temperature.
Acknowledgements This study was supported by a grant from the Danish Ministry of Food, Agriculture and Fisheries under the work programme ‘Sustainable handling and utilisation of animal manure No. BÆR98-DJF-4’.
References Buijsman E; Maas H F M; Asman A H (1987). Anthropogenic NH3 emissions in Europe. Atmospheric Environment, 21, 1009–1022 Fleisher Z; Kenig A; Ravina I; Hagin J (1987). Model of ammonia volatilisation from calcareous soils. Plant and Soil, 103, 205–212
G!enermont S; Cellier P (1997). A mechanistic model for estimating ammonia volatilisation from slurry applied to bare soil. Agricultural and Forest Meteorology, 88, 145–167 Grant R; Blicher-Mathiesen G; Andersen H E; Berg P; Friberg N; Kronvang B; Bak J; Rasmussen P (1993). Landoverv(agningsoplande. Land survey areas. Report No. 87 from DMU, Miljøministeriet-Danmarks Miljøundersøgelser, Copenhagen Hansen M N; Sommer S G; Madsen N P (2003). Reduction of ammonia emission by shallow slurry injection: effects of injection efficiency. Journal of Environmental Quality, 32, 1099–1104. Huijsmans J F M; Hendriks J G L; Vermeulen G D (1998). Draught requirement of trailing-foot and shallow injection equipment for applying slurry to grassland. Journal of Agricultural Engineering Research, 71, 347–356 Hutchings N J; Sommer S G; Andersen J M; Asman W A H (2001). A detailed ammonia emission inventory for Denmark. Atmospheric Environment, 35, 1959–1968 Jenkinson D S (2001). The impact of humans on the nitrogen cycle, with focus on temperate arable agriculture. Plant and Soil, 228, 3–15 Klarenbeek J V; Bruins M A (1991). Ammonia emissions after land spreading of animal slurries. In: Odour and Ammonia Emissions from Livestock Farming (Nielsen V C; Voorburg J H; L’Hermite P, eds), pp. 107–115. Elsevier Applied Science, London Langenakens J; Wilsens K; Cappelle W; Danay P; De Leeuw L; Van Gyseghem D; Dessein D (2001). Development of a measuring device for the transverse distribution of slurry by use of an injector. In: Sustainable Handling and Utilisation of Livestock Manure from Animals to Plants (Rom H B; Sorensen C G, eds), pp. 116–124. Report No. 21-Animal Husbandry, Danish Institute of Agricultural Science, Tjele, Denmark Leuning R; Freney J R; Denmead O T; Simpson J R (1985). A sampler for measuring atmospheric ammonia flux. Atmospheric Environment, 19, 1117–1124 Long F N J; Gracey H I (1990). Herbage production and nitrogen recovery from slurry injection and fertiliser nitrogen application. Grass and Forage Science, 45, 77–82 Misselbrook T H; Hansen M N (2001). Field evaluation of the equilibrium concentration technique (JTI method) for measuring ammonia emission from land spread manure or fertiliser. Atmospheric Environment, 35, 3761–3768 Phillips V R; Pain B F; Klarenbeek J V (1991). Factors influencing the odour and ammonia emissions during and after the land spreading of animal slurries. In: Odour and Ammonia Emissions from Livestock Farming (Nielsen V C; Voorburg J H; L’Hermite P, eds), pp. 98–106. Elsevier Applied Science, London Prins W H; Snijders P J M (1987). Negative effects of animal manure on grassland due to surface spreading and injection. In: Animal Manure on Grassland and Fodder Crops (van der Meer H G; Unwin, R J; Van Dijk T A; Ennik G C, eds), pp. 119–135. Martinus Nijhoff, Dordrecht Sherlock R R; Sommer S G; Rehmat Z; Khan R Z; Wood C W; Guertal E A; Freney J R; Dawson C O; Cameron K C (2002). Emission of ammonia, methane and nitrous oxide from pig slurry applied to a pasture in New Zealand. Journal of Environmental Quality, 31, 1491–1501 Søgaard H T; Sommer S G; Hutchings N J; Huijsmans J F M; Bussink D W; Nicholson F (2002). Ammonia volatilisation
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from field applied animal slurry}The ALFAM model. Atmospheric Environment, 36, 3309–3319 Sommer S G; Ersbøll A K (1994). Soil tillage effects on ammonia volatilisation from surface-applied or injected animal slurry. Journal of Environmental Quality, 23, 493–498 Sommer S G; G!enermont S; Cellier P; Hutchings N J; Morvan T; Olesen J E (2003). Processes of ammonia emission from livestock slurry in the field. European Journal of Agronomy, 19, 465–486 Sommer S G; Hutchings N J; Carton O T (2001). Ammonia losses from field-applied animal manure. Report No. 60Plant Production, Danish Institute of Agricultural Sciences, Tjele, Denmark Sommer S G; Jacobsen O H (1999). Infiltration of slurry liquid and volatilisation of ammonia from surface-applied pig slurry as affected by soil water content. Journal of Agricultural Science, 132, 297–303 Sommer S G; Olesen J E (1991). Effects of dry matter content and temperature on ammonia loss from surface-applied cattle slurry. Journal of Environmental Quality, 20, 679–683 Sommer S G; Olesen J E (2000). Modelling ammonia volatilisation from animal slurry applied with trail hoses to cereals. Atmospheric Environment, 34, 2361–2372 Svensson L (1994). Ammonia volatilisation following application of livestock manure to arable land. Journal of Agricultural Engineering Research, 58, 241–260 Svensson L; Ferm M (1993). Mass transfer coefficient and equilibrium concentration as key factors in a new approach to estimate ammonia emission from livestock manure. Journal of Agricultural Engineering Research, 56, 1–11 Thompson R B; Pain B F; Lockyer D R (1990). Ammonia volatilisation from cattle slurry following surface application to grassland. I. Influence of mechanical separation, changes in chemical composition during volatilisation and the presence of the grass sward. Plant and Soil, 125, 109–117 Wilson J D; Thurtell G W; Kidd G E; Beauchamp E G (1982). Estimation of the rate of gaseous mass-transfer from a surface source plot to the atmosphere. Atmospheric Environment, 16, 1861–1867
volatilisation Fr(t) in kg [N] ha1 h1 is a function of the time tp in hours from slurry application, the application rate Sa in ton slurry ha1 and concentration of TAN in the slurry at time of application TANi in kg [N] t1: F ðtp Þ ðA2Þ Fr ðtp Þ ¼ Sa TANi In two statistical models presented below, an estimate of the concentration of CL (tp) at the soil surface was included as an explanatory variable. The following equation was used (Sherlock et al., 2002) to calculate the NH3 concentration at time tp. Aðtp Þ ðA3Þ CL ðtp Þ ¼ 10pHðtp Þ 1þ 272992 009018 T ðt Þþ273 s p 10 The two models are the result of testing the relationship between Fr(tp) and potential explanatory variables available from the measurements during the experiments characterising climate, soil and slurry (Tables 1–4). The models includes CL equilibrium concentration in slurry. Model 1 calculates C*L in g [N] l1 [Eqn (A3)] using TAN and pH in slurry at time of application and air temperature during the experiment and 1 Model 2 calculates C** [Eqn (A3)] using TAN, pH L in g [N] l and temperature in the surface layer of slurry during the experiment. Variables with a statistical significance level P > 015 were excluded from the models. Model 1 This model uses estimates C*L(tp) by based on the following variables: TAN and pH in the slurry at time of application and air temperature at time tp using Eqn (A3). Model 1 relates the emission of NH3 at time tp to explanatory variables as follows: T ðtp Þ
Fr ðtp Þ ¼ a0 a1 a
uðtp Þ
a2
TANrel ðtp Þ
a3
C ðtp Þ
a4 L
ðA4Þ
where: a0, . . ., a4 are model parameters; Ta(tp) is the air temperature in 8C; TANrel(tp) is the relative amount of TAN in the surface layer; u(tp) is the wind speed in m s1; and C*L(tp) is the equilibrium NH3 concentration in g [N] l1 in the slurry at the soil surface.
Appendix A: Statistical models used for analysis of data To provide aggregated data for assessment of infiltration of chloride Cl1 and TAN, the average amount weighted depth of infiltration Zinf in cm was calculated by the following equation: Zinf ¼
Z8 X
Cz Vz Zz PZ8 Z¼Z1 Z¼Z1 Cz Vz
ðA1Þ
where: C is the concentration of the ions in g l1, V is the volume of soil water in the layer in liters and Z1 2Z8 in cm are the average depths of the layers (depths half-way between the upper and lower boundaries of the layers sampled for analysis, i.e. 0–05, 05–1, 1–15, 15–2, 2–25, 25–35, 35–5, 5–75 cm). Further infiltration was assessed by relating the amount of Cl1 and TAN in the 0–05 cm surface layer to the amount in the entire profile (0–75 cm), i.e. the relative TAN denoted by TANrel and Cl1 concentration Clrel. The relationships between NH3 volatilisation and slurry, soil, climate, infiltration, crop and application data were tested by statistical model analyses. In the models, the relative NH3 volatilisation was used as the dependent variable, i.e. NH3
Model 2 This model uses estimates C** L (tp) by based on the following variables: TAN, pH and temperature in the surface slurry/soil layer at time tp of application using Eqn (6). Model 2 relates the emission of NH3 at time tp to explanatory variables as follows: T ðtp Þ
Fr ðtp Þ ¼ b0 b1 s
uðtp Þ
b2
TANrel ðtp Þ
b3
C ðtp Þ
b4 L
ðA5Þ
where: b0, . . ., b4 are model parameters; Ts(tp) is the slurry/soil surface temperature in 8C at time tp; u(tp) is the wind speed in m s1 at time tp; and C** L (tp) is the equilibrium NH3 concentration in g [N] l1 in the slurry/soil surface layer at time tp. To ensure that the residuals were Gaussian-distributed, logtransformed versions of Models 1 and 2 were used when estimating the model parameters. A similar procedure is explained in more detail in the appendix to the article of Søgaard et al. (2002).
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Infiltration of Slurry and Ammonia Volatilisation S.G. Sommer; M.N. Hansen; H.T. Søgaard Department of Agricultural Engineering, Danish Institute of Agricultural Sciences, Research Centre Bygholm, P.O. Box 536, DK-8700 Horsens, Denmark; E-mail of corresponding author: [email protected] (Received 21 July 2003; accepted in revised form 10 March 2004; published online 15 June 2004)
Volatilisation of ammonia (NH3) from slurry applied in the field reduces the fertiliser value of the slurry and is liable to cause a considerable uncertainty in the nitrogen (N) fertiliser efficiency. A better understanding of slurry–soil interactions is needed in order to develop reliable decision support systems for the use of animal slurry as manure. In this field study, infiltration of slurry in the soil was estimated by measuring chloride (Cl) and ammonium (TAN ¼ NH3+NH+ 4 ) concentrations at different depths from 05 to 75 cm below the soil surface. The NH3 volatilisation was measured using micrometeorological methods and was related to infiltration. Slurry applied to sandy or clay-loam soils infiltrated to 2–25 cm. Ammonium and Cl infiltration could not be related to slurry, soil and climatic variables because the measured infiltration rates were spatially variable. In spite of this spatial variability, the infiltration parameters of TAN explained a large proportion of the variation in NH3 volatilisation. Therefore, reliable models that currently include, wind, soil surface temperature, TAN and pH of applied slurry as parameters for predicting NH3 volatilisation may also benefit by including parameters for TAN infiltration. Models calculations using soil surface TAN concentration, pH and temperature during the volatilisation event are more precise than calculations using air temperature during the study and TAN concentration and pH in slurry at time of application. # 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd
1. Introduction The nitrogen (N) fertiliser efficiency of animal slurry is variable due to volatilisation of ammonia (NH3), uneven spreading of slurry in the field and a low availability of the manure nitrogen (Sommer et al., 2003). The difficulty in assessing the fertiliser value of the manure can lead to a tendency of over-applying N to ensure a good crop growth (Grant et al., 1993). Furthermore, manure from livestock production is considered to be a major source of atmospheric NH3 (Buijsman et al., 1987), which, when deposited, can cause undesirable changes in natural ecosystems (Jenkinson, 2001). To improve plant uptake and reduce N loss to the environment, techniques have been developed for the purpose of improving the fertiliser efficiency of slurry by reducing NH3 volatilisation and improving spreading evenness of slurry in the field. Of these techniques, injection and trail hose application of slurry both seem to hold a potential for reducing NH3 volatilisation and 1537-5110/$30.00
for spreading slurry homogeneously in the field, as compared to the traditional spreading techniques using a splash plate (Sommer et al., 2001). A substantial part of the slurry produced in Denmark is applied to crops during the spring (Hutchings et al., 2001), when the trail hose application technique has a low efficiency in reducing NH3 volatilisation, because crops are low or absent and are not providing shade or shelter for the wind (Hansen et al., 2003). Alternatively, a direct injection technique can be used, but this technique is more labour-intensive and energy-demanding than trail hose application of slurry (Huijsmans et al., 1998; Hansen et al., 2003) and may damage winter-crops (Prins & Snijders, 1987; Long & Gracey, 1990). Furthermore, the effectiveness of injection can be low if the soil is moist and compacted, and the slit remains open (Klarenbeek & Bruins, 1991; Phillips et al., 1991). Efficiency of the trail hose and direct injection may be improved by enhancing the infiltration of slurry liquid into the soil, because increased infiltration will reduce 359
# 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd
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Notation a0 a1 a2 a3 a4
A Ach Azinst b0 b1 b2 b3 b4
C Ceq Ca Cch Cz
Clrel
CL CL
CL
intercept parameter in NH3 emission model model parameter relating NH3 emission to air temperature model parameter relating NH3 emission to wind speed model parameter relating NH3 emission to TANrel model parameter relating NH3 emission to equilibrium NH3 calculated using TAN and pH at the time of slurry application and air temperature at time tp exposed area of the filter used in the JTI technique, m2 area of emitting surface covered by the JTI chamber, m2 effective cross-sectional area of the Leuning sampler, m2 intercept parameter in NH3 emission model model parameter relating NH3 emission to air temperature model parameter relating NH3 emission to wind speed model parameter relating NH3 emission to TANrel model parameter relating NH3 emission to the equilibrium NH3 concentration in the slurry at the soil surface at time tp concentration of NH3 in the air, mg m3 equilibrium concentration of NH3 in the air at the emitting surface, mg [NH3-N] m3 ammonia concentration in the air above the emitting surface, mg [NH3-N] m3 ammonia concentration of air inside the JTI chamber, mg [NH3-N] m3 concentration of Cl1 and total ammonaical nitrogen (TAN) in soil liquid in soil layers Z, g l1 amount of Cl1 in the 0–05 cm surface layer relative to the amount in the entire profile (0– 75 cm) equilibrium concentration of NH3 in the soil slurry mixture, g [N] l1 equilibrium concentration of NH3 in the slurry calculated using TAN and pH in slurry at time of application and air temperature during the experiment, g [N] l1 equilibrium concentration of NH3 in the soil slurry mixture calculated using TAN, pH and
D F Fch Fr ðts Þ Hinst Ka Kch LR LLBL M Q Sa T
tp Ta Ts TANi TANrel
u V X Y Z Zinf ZINST w
temperature in the surface layer of slurry during the experiment, g [N] l1 diffusion coefficient for NH3 in air, m2 s1 ammonia volatilisation rate, mg [NH3-N] m3 s1 flux from the JTI chamber, mg [NH3-N] m3 s1 NH3 emission at time ts relative to applied TAN height at which atmospheric NH3 concentration is measured in the ZINST technique, m mass transfer coefficient for NH3, s1 mass transfer coefficient for NH3 inside the JTI chamber, s1 distance between the Teflon membrane filter and NH3 absorbing filter, m laminar boundary layer above the top of NH3 absorbing filter, m mass of NH3 collected by the Leuning sampler, g [NH3-N] air flow through the JTI chamber, m3 s1 application rate of slurry, t [slurry] ha1 exposure time of the PDS absorbers used to measure NH3 concentration or exposure time of the passive flux samplers used to measure the horizontal flux of NH3, h time from slurry application, h air temperature, 8C soil slurry surface temperature, 8C concentration of TAN in the slurry at time of application, kg [N] t1 amount of TAN in the 0–05 cm surface layer relative to the amount in the entire profile 0– 75 cm wind speed at a single height above the ground, m s1 volume of soil water in the layer Z1 to Z8, l amount of NH3 collected by the PDS-C type, mg [NH3-N] amount of NH3 collected by the PDS-L type, mg [NH3-N] depth of the soil layer, cm average amount weighted depth of infiltration of chloride Cl1 and TAN, cm unit flux uw/F ratio used by the ZINST technique atmospheric NH3 concentration at the Hinst height, mg [NH3-N] m3
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NH3 volatilisation (Sommer & Olesen, 1991; Sommer & Ersbøll, 1994; Thompson et al., 1990). A high slurry and dry matter content (DM) of slurry may reduce infiltration of slurry, therefore, NH3 volatilisation is reduced by reducing viscosity and DM by separation, fermentation in a biogas reactor or diluting the slurry (Sommer et al., 2003). In this paper, six field experiments were conducted to relate infiltration as affected by category of animal producing the slurry, slurry treatment and soil type. Ammonia volatilisation was related to infiltration of slurry into the soil, slurry characteristics and soil condition. The main objective was to contribute to the development of reliable decision support systems for slurry application, with the purpose of reducing NH3 volatilisation.
2. Materials and methods 2.1. Study site Ammonia volatilisation from slurry applied with a trail hose to six different soils was studied in six experiments at two sites in Denmark; a farm in the western part of Jutland and at Research Centre Bygholm in the eastern part of Jutland (Table 1). The study sites were either fallow, or spring barley, or grass fields. The cereals were drilled in rows 12 cm apart. The soil in western Jutland is classified as a sandy soil and the soil at Research Centre Bygholm as a clay loam. To provide an option for comparing the effect of different soil textures under similar climate conditions, a 20 cm layer of sandy soil was laid out in a 20 m by 20 m square in the field at Research Centre Bygholm in the October 2000 and April 2001 experiments. In arable fields the top soil is cultivated several times a year, therefore, a 20 cm
layer of ‘new’ top soil will represent the surface of a field when measuring infiltration of slurry into the soil within one week after slurry application i.e. the period with significant volatilisation of NH3. In the six experiments, slurry was applied at rates from 300 to 377 m3 ha1. The slurry was spread with a trail hose spreader equipped with 40 trail hoses mounted 30 cm apart on a 12 m spreading bar. The bar was mounted 1 m above the soil surface but the trail hoses allowed the slurry to be placed exclusively on the soil between the rows of plants. In the experiments started on 10 October 2000, 3 April 2001 and 24 April 2001, slurry was applied in 20 m by 20 m parcels covering the sandy soil plot and the sandy loam Bygholm soil. In the experiments started on 30 May 2000, 15 May 2001 and 7 May 2002, slurry was applied to square experimental plots (36 m by 36 m). Application rates and characteristics of the pig slurries used in the study are presented in Tables 2 and 3. Meteorological data (Table 4) were obtained from the meteorological station at Research Centre Bygholm, located less than 500 m from the experimental sites, and the meteorological station at approximately 20 km from the farm in western Jutland. Data used in this study were 10 min values of air temperature (2 m), soil temperature (01 m), wind speed (10 m), incident solar radiation (20 m) and precipitation (15 m). During the experiments from May 2000 to April 2001, soil surface temperature was measured with a standard thermocouple temperature sensor pushed into the upper 05 cm of the soil surface. 2.2. Soil analysis In each plot two soil cores from 0–75 cm depths were collected with steel cylinders (0097 m in diameter by
Table 1 Characteristics of soil and crop to which slurry was applied in this study, a plow layer was provided by laying out a 20 cm layer of sandy soil in the experiment with application date 10th October 2000, 3rd and 24th of April 2001 Application date
30 May 2000 10 Oct 2000, 3 April 2001 and 24 April 2001 10 Oct 2000 3 April 2001 and 24 April 2001 15 May 2001 7 May 2002 ND, not determined. OM, organic matter.
Clay, 52 mm % w/w
Loam, 2–20 mm % w/w
Loam, 20–63 mm % w/w
Sand, 63–200 mm % w/w
Sand, % w/w
OM % w/w
C % w/w
Crop
13 111
15 135
136 103
274 334
269 285
38 31
ND 18
Grass 5 cm None
75 42
12 38
125 33
393 164
257 695
3 28
18 16
None None
235 103
24 122
135 127
1585 281
751 334
30 34
173 198
Spring Barley 7 cm Spring barley 5 cm
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Table 2 Characteristics of the slurry applied to fields in the experiments Application date
30 10 3 24 15 15 15 15 15 7 7 7
Animal
May 2000 Oct 2000 April 2001 April 2001 May 2001 May 2001 May 2001 May 2001 May 2001 May 2002 May 2002 May 2002
Treatment
Cattle Cattle Cattle Pig Pig Pig Pig Pig Pig Pig Pig Pig
Manure composition
No No No No No Diluted Digested Digested, separated Digested, separated, diluted No Digested Digested, separated
pH
TAN, g kg1
Cl, g kg1
Total-N, g kg1
DM, %
71 74 71 ND ND 69 81 85 84 736 809 827
160 110 131 072 072 19 44 51 25 307 37 36
077 077 123 041 041 ND ND ND ND ND ND ND
352 370 251 178 178 24 45 54 26 43 51 48
863 501 955 138 138 160 280 298 13 328 323 215
ND, not determined. DM, dry matter content of slurry.
Table 3 Characteristics of soil water, application rate and width of slurry band Application date 30 10 3 24 10 3 24 15 7
Soil water, vol %
Application rate, t ha1
253 307 215 193 272 169 129 112–226 ND
30 30 336 30 30 336 300 377 266
May 2000 Oct 2000 April 2001 April 2001 Oct 2000* April 2001* April 2001* May 2001 May 2002
Width of slurry band, cm 125 74 74 30 74 74 300 10 ND
In the experiment starting the 15th of May 2001 the plot to which slurry was applied in the morning was dry, at later application of slurry rain during increased soil surface water content. ND, not determined. * A plough layer was provided by laying out a 20 cm layer of sandy soil in the experiment with application date 10th October 2000, 3rd and 24th April 2001, therefore two different soils were included in the experiments.
Table 4 Mean air and soil temperature, solar radiation and wind, and cumulated rain during the experimental periods Measuring period Start
End
30 10 3 24 15 7
13 June 2000 16 Oct 2000 9 April 2001 20 April 2001 22 May 2001 14 May 2002
May 2000 Oct 2000 April 2001 April 2001 May 2001 May 2002
ND, Not determined.
Air temperature, 8C
Soil temperature,8C
113 98 77 91 1129 126
111 89 58 71 1250 120
Radiation, W m2 ND 7232 11 893 19 633 6609 ND
Wind speed, m s1
Rain, mm
45 77 61 42 278 52
205 7 19,4 27,2 42 04
ARTICLE IN PRESS VOLATILISATION OF AMMONIA FROM SLURRY
008 m in height) that were pushed into the soil in the middle of the slurry bands. The soil columns were sliced into segments (0–05, 05–1, 1–15, 15–2, 2–25, 25–35, 35–5, 5–75 cm) by carefully pushing up the soil with a piston and cutting of the excess soil extending over the top of the core. Soil-water content was determined by drying a sub-sample from each slice at 1058C for 24 h. Ammonium (TAN ¼ NH3+ NH+ 4 ) content was extracted with 10 M potassium chloride for 05 h and Cl with deionised water for 05 h. The ammonium and Cl contents were determined colorimetrically using a spectrophotometer (Shimadzu UV-120-01, Japan) for TAN and a Merck-Spectroquant NOVA 60 (Darmstad, Germany) for Cl determination. At soil sampling soil slurry surface pH was measured with a flat-headed pH electrode and a portable pH-meter (Radiometer, PHM80 portable pH meter, Copenhagen, DK). In each experiment soil were sampled 3 h after application of slurry to the plot and in experiments with slurry application the 30 May 2000, 10 October 2000, 3 April 2001 and 24 April 2001 soil was sampled 1, 3, 7, 24, 48, 73, 145 h after slurry application. 2.3. Ammonia volatilisation In the experiments started on 10 October 2000, 3 April 2001 and 24 April 2001, NH3 volatilisation was determined with the JTI method (Misselbrook & Hansen 2001). The JTI method uses the micrometeorological law of resistance to determine the horizontal flux of NH3 (F in mg [NH3-N] m3 s1) from the equilibrium concentration of NH3 in the air at the emitting surface Ceq in mg [NH3-N] m3, the NH3 concentration in the air above the emitting surface (Ca in mg [NH3-N] m3) and the mass transfer coefficient for NH3 (Ka in s1) F ¼ ðCeq Ca Þ Ka
ð1Þ
Passive diffusion samplers (PDS) are used to measure NH3 concentration in the air. Two types of PDS are used which differ in the length of the diffusion path. For the L-type, the NH3 absorbing filter is placed at the top, directly exposed to the ambient air. The C-type has the NH3 absorbing filter placed 10 mm below a Teflon membrane filter. The amount of NH3 collected by the PDS-C type (X in mg) and PDS-L type (Y in mg) is given by A X ¼ DCt ð2Þ LR LLBL and Y ¼ DCt
A LLBL
ð3Þ
363
respectively, where D is the diffusion coefficient for NH3 in air in m2 s1, C the concentration of NH3 in the air in mg m3, t the sampling time for the PDS in s, A the exposed area of the filter in m2, LR the distance in m between the Teflon membrane filter and the NH3 absorbing filter for PDS-C type and LLBL the laminar boundary layer in m above the top of the PDS. By combining Eqns (2) and (3), an expression for LLBL can be derived: XLR ð4Þ LLBL ¼ ðY X Þ The mass transfer coefficient can then be derived from the relationship D Ka ¼ ð5Þ LLBL By using the two types of PDS close to the surface of a treated plot, both the concentration of NH3 in the air just above the emitting surface and the mass transfer coefficient can be determined from Eqns (2)–(5). The other parameter required in Eqn (1), Ceq, is determined by use of a ventilated chamber. The chamber is ventilated by a fan via small inlet and outlet openings at one end, to ensure that condensation does not form on the internal walls. Inlet air to the chamber is assumed to have an NH3 concentration Ca, as measured by the PDS outside the chamber. The NH3 flux from the area (Fch in mg [NH3-N] m3 s1) covered by the chamber can be calculated according to Eqn (1) as Fch ¼ Ceq Cch Kch ð6Þ where Cch is the NH3 concentration of air inside the chamber in mg [NH3-N] m3 and Kch the mass transfer coefficient for NH3 inside the chamber in s1 (which should be constant for a given flow rate and surface conditions). The flux Fch in mg from the chamber can also be calculated by mass balance ðCch Ca ÞQ Fch ¼ ð7Þ Ach where Q is the air flow rate through the chamber in m3 s1 and Ach the area of emitting surface covered by the chamber in m2. Combining Eqns (6) and (7) gives an expression for the equilibrium concentration at the emitting surface Q=Ach Q=Ach Ceq ¼ Cch 1 þ Ca ð8Þ Kch Kch This can then be used in Eqn (1) together with the determined values for Ca and Ka, to derive the flux from the treated area for the measurement period. More information about the method is presented by Svensson and Ferm (1993) and Svensson (1994). Three chambers were used to estimate the emission from each plot and
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the emission was determined for the time intervals: 0–1, 1–3, 3–7, 7–24, 24–48, 48–144 h. In the experiments started on 30 May 2000, 15 May 2001 and 7 May 2002, NH3 volatilisation was measured with the micrometeorological mass balance method described by Wilson et al. (1982). The volatilisation can be inferred from measurements of increase in atmospheric NH3 concentration in the air parcels passing the experimental plot w in mg [NH3-N] m3 and wind speed u in m s1 at a single height Hinst in m above the ground uw F¼ ð9Þ ZINST The term ZINST is the unit flux uw/F ratio, which is given by Wilson et al. (1982). The horizontal flux (uw) was measured using passive Leuning samplers (Leuning et al., 1985) mounted at the Hinst height 09 m above the soil surface, on masts placed at the upwind edge and at the centre of the plot (radius 18 m). According to Leuning et al. (1985), uw is derived from M ð10Þ uw ¼ Azinst t where M is the mass of NH3-N in g collected by coating the interior of the Leuning sampler with oxalic acid during sampling period t in s and Azinst is the effective cross-sectional area of the sampler in m2 determined in wind-tunnel calibrations. After exposure, the coating was dissolved in 0040 l of deionised water and the NH4-N content in g l1 determined by the indophenol blue colorimetric method using a spectrophotometer (Shimadzu UV-120-01, Japan). Two space shuttles were used to estimate the emission from each plot and the emission was determined for the time intervals: 0–2, 2–6, 6–23, 23–50, 50–71, 71–98, 98–166 h.
3. Results and discussion Figure 1 shows that the TAN and Cl concentrations in the soil are elevated due to infiltration of slurry liquid to a depth of 2–25 cm below the soil surface underneath a slurry band. The fraction of TAN near the soil surface is higher than the fraction of Cl , and in Fig. 2 the infiltration of TAN is related to the infiltration of Cl (probability P5001), showing that a larger fraction of Cl is infiltrating to greater depth than is the case for TAN, indicating that NH+ 4 has been absorbed in the surface layers by soil colloids. Ammonium is retained by soil cation exchange capacity (Fleisher et al., 1987) and therefore transport of NH+ 4 infiltration lags behind the waterfront into the soil. On the other hand, the negative ion Cl is not retained by absorption to the negatively charged soil colloids and is therefore transported convectively with soil water. In a laboratory study, applying 3 l m2 slurry to soils packed in columns; the maximum infiltration depth of the conservative ion bromide (Br) was 175 cm (Sommer & Jacobsen, 1999). Statistical analyses did not indicate significant relationships between infiltration (of Cl and TAN) and slurry composition, soil and climate. One reason for this is that measurements of infiltration in the field are highly variable due to heterogeneous soil surfaces with small pits in which slurry forms ponds; furthermore, uneven spreading of slurry in field experiments contributes to spatially uneven volumes of slurry applied in the plots (Langenakens et al., 2001). In the present study the variations in slurry applied per site are larger than the differences in infiltration due to different soils and slurries. Two statistical models were applied for analysis of the relationship between ammonia volatilisation and other
2.0 1.5 1.0
3
2
1
0.5 0.0
(a)
4
TAN, g[N] l −1
Chloride, g [Cl] l −1
2.5
0
1
2 Depth, cm
3
0 0
4 (b)
1
2
3
4
Depth, cm
Fig. 1. (a) Concentration profile of chloride and (b) total ammoniacal nitrogen (TAN) 3 h after application of pig slurry in May 2002; pre- treatment of the pig slurries were: - - * - - , untreated; }* –, anaerobic digested; – . – , anaerobic digested and separated
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variables (see Appendix A for mathematical equations). Model 1 demands knowledge of TAN and pH in the slurry applied, the amount of TAN in the 0–05 cm surface layer relative to that in full profile of 0–75 cm, denoted by TANrel, after application of slurry, and air temperature and wind speed during the volatilisation
TAN, average depth cm
2.5 2.0 1.5 1.0 0.5 0.0 0.0
0.5
1.0
1.5
2.0
2.5
3.0
Chloride, average depth cm Fig. 2. Infiltration of total ammoniacal nitrogen (TAN) as a function F of chloride infiltration expressed as weighted average depth of infiltration [Eqn (4)]; coefficient of determination R2 ¼ 029, F ¼ 034x þ 058
event, as NH3 volatilisation was shown to be significantly (P501, Table 5) related to these variables. In Model 1 [Eqn (A4)] the air temperature Ta in 8C for the time from slurry application tp in h is represented explicitly through the factor a1Ta ðtP Þ and implicitly C ðt Þ through the factor a4 L P , since the estimate of the equilibrium NH3 concentration CL ðtP Þ in g [N] l1 is a function of air temperature. Equilibrium between slurry NH3 and atmospheric NH3 are not included in the model; the effect of this process on NH3 volatilisation can therefore be expressed as an effect of air temperature, because temperature is included when calculating the equilibrium between liquid and atmospheric NH3 (Henry’s constant, G!enermont & Cellier, 1997). In Model 2 [Appendix A, Eqn (A5)], NH3 volatilisation is significantly (P501) related to soil temperature, wind speed, relative TAN concentration and NH3 concentrations (Table 5). As in Model 1, temperature has a significant effect on NH3 volatilisation due to its impact on the equilibrium between NH3 in solution and atmospheric NH3 (G!enermont & Cellier, 1997). Model 2 (the coefficient of determination R2 ¼ 077), which includes NH3 concentration calculated from Eqn (A3) using TAN, pH and temperature in the slurry soil mixture, is more precise than Model 1 (R2 ¼ 063), which is based on bulk concentrations of TAN and pH in the
Table 5 Results of the statistical analysis; Model 1 [Eqn (7)] is based on 76 observations of ammonia emission and the value for the coefficient of determination R2 is 0.63; Model 2 [Eqn (8)] is based on only 51 observations of ammonia emission and the value for R2 is 0.77; the number of observations used for Model 2 is lower than the number of observations used for Model 1 due to missing estimates of C,L**; variables significant at probability P50.15 are included in the models Model 1
2
Experimental factor
Parameter estimate
None Air temperature Ta
43–1348C
a0 ¼ 93 107 a1 ¼ 137
Wind speed u
20–107 m s1
a2 ¼ 154
Relative ammonium conc. in slurry/soil surface TANrel Estimated NH3 concentrationa C*L
15–84%
a3 ¼ 107
0002–0320 g l1
a4 ¼ 115 106
43–1078C
b0 ¼ 75 107 b1 ¼ 122
33–107 m s1
b2 ¼ 187
27–83%
b3 ¼ 105
0002–0028 g l1
b4 ¼ 117 1030
None Temperature of soil surface/ slurry Ts Wind speed u Relative ammonium conc. in slurry/soil surface TANrel Estimated NH3 concentrationb C** ,L a
Range
Effect on NH3 emission +37% per 8C increase in air temp +54% per m s1 increase in wind speed +7% per % increase in TANrel conc. +15% per 0.01 g/l increase in NH3 conc. +22% per 8C increase in air temperature +87% per m s1 increase in wind speed +5% per % increase in TANrel conc. +100% per 001 g/l increase in NH3 conc.
95% confidence interval +18 60% +38% 73% +5 9% +7% 23%
5 57% +63% 114% +3 8% +2% 192%
The CL concentration was estimated from air temperature, initial TAN concentration and pH in the slurry using Eqn (A3). The CL concentration was estimated from TAN, pH and temperature in the surface slurry/soil layer at time t of application using Eqn (A3). b
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applied slurry and air temperature. This is to be expected because NH3 equilibrium is more precisely estimated by using the composition and surface temperature of slurry and soil mixture, as TAN and pH in slurry on the soil will be different from the initial composition of the slurry due to volatilisation of NH3 and changes in pH (G!enermont & Cellier, 1997; Sommer & Olesen, 2000). In decision support systems, initial TAN concentrations and pH of the slurry, soil surface temperature, wind and a submodel for infiltration can be used to predict NH3 volatilisation. This study indicated that models for predicting pH of the surface of slurry and soil mixture can improve the models significantly. The results suggest that relating NH3 volatilisation to the proportion of TAN in the topsoil/slurry layer can contribute to modelling the effect of TAN infiltration. In studies of NH3 volatilisation it can be appropriate to assess infiltration by measuring TAN in the surface layer and relating it either to the amount of TAN in the soil or to the amount of TAN applied in slurry. Thereby, infiltration can be characterised with two analyses per soil sampling, i.e. soil and slurry surface sample and a sample from 0 to 5 cm.
4. Conclusions Infiltration of chloride (Cl1) from slurry applied to sandy or sandy loam soils was spatially very variable. The Cl1 infiltration was between 2 and 3 cm in this field study and Cl1 was infiltrating to greater depths than ammonium. Ammonium concentration in soil samples and infiltration of ammonium explained a significant part of the variation in NH3 volatilisation. Ammonia volatilisation was also related to wind, soil surface temperature and air temperature.
Acknowledgements This study was supported by a grant from the Danish Ministry of Food, Agriculture and Fisheries under the work programme ‘Sustainable handling and utilisation of animal manure No. BÆR98-DJF-4’.
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G!enermont S; Cellier P (1997). A mechanistic model for estimating ammonia volatilisation from slurry applied to bare soil. Agricultural and Forest Meteorology, 88, 145–167 Grant R; Blicher-Mathiesen G; Andersen H E; Berg P; Friberg N; Kronvang B; Bak J; Rasmussen P (1993). Landoverv(agningsoplande. Land survey areas. Report No. 87 from DMU, Miljøministeriet-Danmarks Miljøundersøgelser, Copenhagen Hansen M N; Sommer S G; Madsen N P (2003). Reduction of ammonia emission by shallow slurry injection: effects of injection efficiency. Journal of Environmental Quality, 32, 1099–1104. Huijsmans J F M; Hendriks J G L; Vermeulen G D (1998). Draught requirement of trailing-foot and shallow injection equipment for applying slurry to grassland. Journal of Agricultural Engineering Research, 71, 347–356 Hutchings N J; Sommer S G; Andersen J M; Asman W A H (2001). A detailed ammonia emission inventory for Denmark. Atmospheric Environment, 35, 1959–1968 Jenkinson D S (2001). The impact of humans on the nitrogen cycle, with focus on temperate arable agriculture. Plant and Soil, 228, 3–15 Klarenbeek J V; Bruins M A (1991). Ammonia emissions after land spreading of animal slurries. In: Odour and Ammonia Emissions from Livestock Farming (Nielsen V C; Voorburg J H; L’Hermite P, eds), pp. 107–115. Elsevier Applied Science, London Langenakens J; Wilsens K; Cappelle W; Danay P; De Leeuw L; Van Gyseghem D; Dessein D (2001). Development of a measuring device for the transverse distribution of slurry by use of an injector. In: Sustainable Handling and Utilisation of Livestock Manure from Animals to Plants (Rom H B; Sorensen C G, eds), pp. 116–124. Report No. 21-Animal Husbandry, Danish Institute of Agricultural Science, Tjele, Denmark Leuning R; Freney J R; Denmead O T; Simpson J R (1985). A sampler for measuring atmospheric ammonia flux. Atmospheric Environment, 19, 1117–1124 Long F N J; Gracey H I (1990). Herbage production and nitrogen recovery from slurry injection and fertiliser nitrogen application. Grass and Forage Science, 45, 77–82 Misselbrook T H; Hansen M N (2001). Field evaluation of the equilibrium concentration technique (JTI method) for measuring ammonia emission from land spread manure or fertiliser. Atmospheric Environment, 35, 3761–3768 Phillips V R; Pain B F; Klarenbeek J V (1991). Factors influencing the odour and ammonia emissions during and after the land spreading of animal slurries. In: Odour and Ammonia Emissions from Livestock Farming (Nielsen V C; Voorburg J H; L’Hermite P, eds), pp. 98–106. Elsevier Applied Science, London Prins W H; Snijders P J M (1987). Negative effects of animal manure on grassland due to surface spreading and injection. In: Animal Manure on Grassland and Fodder Crops (van der Meer H G; Unwin, R J; Van Dijk T A; Ennik G C, eds), pp. 119–135. Martinus Nijhoff, Dordrecht Sherlock R R; Sommer S G; Rehmat Z; Khan R Z; Wood C W; Guertal E A; Freney J R; Dawson C O; Cameron K C (2002). Emission of ammonia, methane and nitrous oxide from pig slurry applied to a pasture in New Zealand. Journal of Environmental Quality, 31, 1491–1501 Søgaard H T; Sommer S G; Hutchings N J; Huijsmans J F M; Bussink D W; Nicholson F (2002). Ammonia volatilisation
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from field applied animal slurry}The ALFAM model. Atmospheric Environment, 36, 3309–3319 Sommer S G; Ersbøll A K (1994). Soil tillage effects on ammonia volatilisation from surface-applied or injected animal slurry. Journal of Environmental Quality, 23, 493–498 Sommer S G; G!enermont S; Cellier P; Hutchings N J; Morvan T; Olesen J E (2003). Processes of ammonia emission from livestock slurry in the field. European Journal of Agronomy, 19, 465–486 Sommer S G; Hutchings N J; Carton O T (2001). Ammonia losses from field-applied animal manure. Report No. 60Plant Production, Danish Institute of Agricultural Sciences, Tjele, Denmark Sommer S G; Jacobsen O H (1999). Infiltration of slurry liquid and volatilisation of ammonia from surface-applied pig slurry as affected by soil water content. Journal of Agricultural Science, 132, 297–303 Sommer S G; Olesen J E (1991). Effects of dry matter content and temperature on ammonia loss from surface-applied cattle slurry. Journal of Environmental Quality, 20, 679–683 Sommer S G; Olesen J E (2000). Modelling ammonia volatilisation from animal slurry applied with trail hoses to cereals. Atmospheric Environment, 34, 2361–2372 Svensson L (1994). Ammonia volatilisation following application of livestock manure to arable land. Journal of Agricultural Engineering Research, 58, 241–260 Svensson L; Ferm M (1993). Mass transfer coefficient and equilibrium concentration as key factors in a new approach to estimate ammonia emission from livestock manure. Journal of Agricultural Engineering Research, 56, 1–11 Thompson R B; Pain B F; Lockyer D R (1990). Ammonia volatilisation from cattle slurry following surface application to grassland. I. Influence of mechanical separation, changes in chemical composition during volatilisation and the presence of the grass sward. Plant and Soil, 125, 109–117 Wilson J D; Thurtell G W; Kidd G E; Beauchamp E G (1982). Estimation of the rate of gaseous mass-transfer from a surface source plot to the atmosphere. Atmospheric Environment, 16, 1861–1867
volatilisation Fr(t) in kg [N] ha1 h1 is a function of the time tp in hours from slurry application, the application rate Sa in ton slurry ha1 and concentration of TAN in the slurry at time of application TANi in kg [N] t1: F ðtp Þ ðA2Þ Fr ðtp Þ ¼ Sa TANi In two statistical models presented below, an estimate of the concentration of CL (tp) at the soil surface was included as an explanatory variable. The following equation was used (Sherlock et al., 2002) to calculate the NH3 concentration at time tp. Aðtp Þ ðA3Þ CL ðtp Þ ¼ 10pHðtp Þ 1þ 272992 009018 T ðt Þþ273 s p 10 The two models are the result of testing the relationship between Fr(tp) and potential explanatory variables available from the measurements during the experiments characterising climate, soil and slurry (Tables 1–4). The models includes CL equilibrium concentration in slurry. Model 1 calculates C*L in g [N] l1 [Eqn (A3)] using TAN and pH in slurry at time of application and air temperature during the experiment and 1 Model 2 calculates C** [Eqn (A3)] using TAN, pH L in g [N] l and temperature in the surface layer of slurry during the experiment. Variables with a statistical significance level P > 015 were excluded from the models. Model 1 This model uses estimates C*L(tp) by based on the following variables: TAN and pH in the slurry at time of application and air temperature at time tp using Eqn (A3). Model 1 relates the emission of NH3 at time tp to explanatory variables as follows: T ðtp Þ
Fr ðtp Þ ¼ a0 a1 a
uðtp Þ
a2
TANrel ðtp Þ
a3
C ðtp Þ
a4 L
ðA4Þ
where: a0, . . ., a4 are model parameters; Ta(tp) is the air temperature in 8C; TANrel(tp) is the relative amount of TAN in the surface layer; u(tp) is the wind speed in m s1; and C*L(tp) is the equilibrium NH3 concentration in g [N] l1 in the slurry at the soil surface.
Appendix A: Statistical models used for analysis of data To provide aggregated data for assessment of infiltration of chloride Cl1 and TAN, the average amount weighted depth of infiltration Zinf in cm was calculated by the following equation: Zinf ¼
Z8 X
Cz Vz Zz PZ8 Z¼Z1 Z¼Z1 Cz Vz
ðA1Þ
where: C is the concentration of the ions in g l1, V is the volume of soil water in the layer in liters and Z1 2Z8 in cm are the average depths of the layers (depths half-way between the upper and lower boundaries of the layers sampled for analysis, i.e. 0–05, 05–1, 1–15, 15–2, 2–25, 25–35, 35–5, 5–75 cm). Further infiltration was assessed by relating the amount of Cl1 and TAN in the 0–05 cm surface layer to the amount in the entire profile (0–75 cm), i.e. the relative TAN denoted by TANrel and Cl1 concentration Clrel. The relationships between NH3 volatilisation and slurry, soil, climate, infiltration, crop and application data were tested by statistical model analyses. In the models, the relative NH3 volatilisation was used as the dependent variable, i.e. NH3
Model 2 This model uses estimates C** L (tp) by based on the following variables: TAN, pH and temperature in the surface slurry/soil layer at time tp of application using Eqn (6). Model 2 relates the emission of NH3 at time tp to explanatory variables as follows: T ðtp Þ
Fr ðtp Þ ¼ b0 b1 s
uðtp Þ
b2
TANrel ðtp Þ
b3
C ðtp Þ
b4 L
ðA5Þ
where: b0, . . ., b4 are model parameters; Ts(tp) is the slurry/soil surface temperature in 8C at time tp; u(tp) is the wind speed in m s1 at time tp; and C** L (tp) is the equilibrium NH3 concentration in g [N] l1 in the slurry/soil surface layer at time tp. To ensure that the residuals were Gaussian-distributed, logtransformed versions of Models 1 and 2 were used when estimating the model parameters. A similar procedure is explained in more detail in the appendix to the article of Søgaard et al. (2002).