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SE—Structures and Environment
Biosystems Engineering (2002) 82 (4), 455–462 doi:10.1006/bioe.2002.0081. available online at http://www.idealibrary.com on SE}Structures and Environment
Ammonia Emissions from Broiler Manure } Influence of Storage and Spreading Method Lena Rodhe; Stig Karlsson JTI } Swedish Institute of Agricultural and Environmental Engineering, P.O. Box 7033, S-750 07 Uppsala, Sweden; e-mail of corresponding author: [email protected] (Received 5 May 2001; accepted in revised form 12 April 2002; published online 11 July 2002)
Knowledge is poor concerning losses of ammonia from broiler manure during storage and after spreading. Broiler manure was stored from October to May in two separate heaps, one uncovered and one covered with a 30 cm layer of straw. Ammonia emissions were measured with a micrometeorological mass balance method in five separate periods during storage. Ambient air temperature and temperatures in the heaps were recorded continuously. After storage, broiler manure from the uncovered heap and commercial fertilizer pellets including broiler manure were spread to arable land at a rate of 110 kg [total-N] ha1. Ammonia emissions were measured with an equilibrium concentration method from plots fertilized with broiler manure and pellets, respectively, with and without harrowing 4 h after spreading. Temperature measurements taken in the heaps during storage indicated high biological activity. The highest temperatures were recorded in the strawcovered heap. Cumulative ammonia losses were 7% of total nitrogen from the uncovered heap and 10% from the heap with cover. Totally, 135% of the nitrogen in the broiler manure was lost as ammonia after spreading without incorporation of the manure and 75% from plots with incorporation. After incorporation no ammonia emission occurred. No emissions occurred from plots fertilized with pellets. # 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved
1. Introduction In Sweden, broiler manure is increasingly sold as commercial fertilizer with organic farming being the principal market. However, knowledge is poor about nutrient losses from broiler manure during storage and after spreading in crop production. Approximately 47 400 t [N] year1 are emitted from Swedish agriculture in the form of ammonia (SCB, 1998), corresponding to about 90% of the total amount of ammonia released in Sweden. Most of this nitrogen originates from manure and its loss not only contributes to eutrophication and acidification, but also represents a loss of a valuable plant macronutrient. In relation to fresh cattle and pig excreta, fresh poultry excreta have a high concentration of nitrogen (Kirchmann & Witter, 1992). Fresh faeces from poultry contains nitrogen in the form of uric acid (61%), organically bound nitrogen (31%) and ammonia (8%) (Kirchmann, 1991). After excretion, the uric acid and undigested proteins degrade, resulting in the formation 1537-5110/02/ $35.00
of ammonia, which can be lost by volatilization (Groot Koerkamp, 1994). The degradation processes are microbial mediated and require the presence of water and oxygen. According to Elliot and Collins (1983), the ammonia release is highest from manure with dry matter contents between 40 and 60%. Groot Koerkamp (1994) stated that the minimum ammonia emission from manure is achieved if a dry matter content of 60% is reached within 50 h after excretion of the faeces (this minimizes the degradation of uric acid and undigested proteins). Studies of stored broiler manure (Kroodsma et al., 1988) in a ventilated container unit showed a positive relationship between low NH3 emissions and dry manure. For moist broiler manure (55% DM), the spontaneous generation of heat tended to be short and considerable, whilst the accompanying NH3 emission was high at the start of storage period. Kirchmann (1985) showed a clear relationship between the initial C/N ratio and the magnitude of ammonia losses from poultry 455
# 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved
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L. RODHE; S. KARLSSON
manure stored under aerobic conditions. The study was performed as a laboratory incubation experiment with poultry manure and oat straw litter during aerobic and anaerobic conditions. Under anaerobic decomposition conditions, hardly any ammonia losses occurred, but during aerobic conditions the losses were high. The highest losses, 40% of the manure nitrogen, were achieved from the manure with the lowest C/N (18). Jeppsson et al. (1997) showed that the choice of bedding material in the livestock buildings could considerably influence the ammonia losses during storage of cattle manure. Only 2% of the nitrogen was lost as ammonia when peat and chopped straw were used as mixed litter compared to a 23% loss with untreated straw as litter. Puumala (2001) tested peat as a cover on a manure heap with broiler peat litter and measured temperatures, effluents and estimated ammonia losses. The temperatures in the covered heap declined more slowly than in the uncovered heap. The estimated ammonia losses were reduced by 80–90% when the peat cover was used compared to the uncovered heap. There is also evidence that straw, used as a surface cover, can reduce ammonia emissions from slurry storages (Sommer et al., 1993; Ho. rnig et al., 1999). Ammonia losses after spreading of broiler manure have been measured by Lockyer and Pain (1989) and Chambers et al. (1997), see Table 1. In all three experiments, the manure was applied to growing crops and the losses were between 7 and 14% of the total-N in the broiler manure. Measures to reduce ammonia emissions after spreading of solid manure on arable land have been studied by Malgeryd (1998). An effective way to reduce ammonia emissions is to incorporate the manure into the soil after spreading. By harrowing 4 h after spreading of solid manure on bare soil, emissions were reduced by almost 90% compared to the situation where no incorporation was made. Furthermore, animal manure spread on bare soil should be incorporated within 4 h in the southernmost regions of Sweden. This regulation was adopted in 1996 (SJV, 1998). Irrigation after spreading of solid manure is
another method which can reduce ammonia emissions (Rodhe et al., 1996). The aim of the work was to investigate how different handling methods of broiler manure affect ammonia emissions and manure properties. Measures compared were presence and absence of a straw cover during storage, and incorporation and non-incorporation of the surface spread manure.
2. Materials and methods 2.1. Storing The manure used, consisted of faeces from chickens (from 1-day old to about 5 weeks of age) and a bed of wood shavings placed in the broiler house at the start of the growing period. The broiler manure was removed from the stable, and temporarily stored in steel containers outside the broiler chicken house for about a week. Thereafter, it was transported to the experimental site located in the eastern part of the Svealand district of Sweden, at 598500 N178480 E. Here, the manure was studied during a storage period of 7 months, from the end of October until the end of May. The manure was placed in two separate heaps, one uncovered and one covered with a 30 cm layer of straw. Each heap was approximately 40 m wide at ground level, 110 m long and 11 m high. The mass of the uncovered heap was 15 300 kg, while the corresponding figure for the covered heap was 16 000 kg, straw cover excluded. A net was placed on top of the covered heap to ensure stability of the straw layer. Bulk density, dry matter content, pH and nutrient content of the manure were measured at the start and at the end of the storage period. For measuring bulk density, a specially made ‘characterization box’ was used (Malgeryd, 1994). The box held 13 m3 of manure and was handled and filled with a tractor-mounted front loader. Bulk density was measured by weighing the whole box for three samples per heap. Manure samples were taken for chemical
Table 1 Manure analysis, application rate, nitrogen losses as ammonia after spreading, and measuring period for three different broiler manures Dry matter, %
75 639 587 *
NH4 –N*, %
057 094 134
Tot-N, %
Rate, t ha1
295 311 305
Chambers et al. (1997) included uric acid-N.
60 69 99
N-losses % of NH4 -N
% of tot-N
372 46 15
72 14 7
Measuring period, days
References
6 9 23
Lockyer & Pain, (1989) Chambers et al., (1997) Chambers et al., (1997)
AMMONIA EMISSIONS FROM BROILER MANURE
analyses taken from the middle of each box with a pitchfork. One sample was taken when the box was half filled and one when it was completely filled. Standards from SIS (2000), DIN (1988) and APHA (1985) were used for analysing dry matter, pH and nutrient content. Ambient air temperature and heap temperatures were recorded continuously. Heap temperatures were measured at eight different locations in each heap. The precipitation during the storage period was 300 mm measured at Ultuna meteorological station situated 598490 N178480 E, about 10 km west of the experimental site (SLU, 1997, 1998). For measuring ammonia emissions, a micrometeorological mass balance method was used, described by Schjørring et al. (1992) and applied by Karlsson (1994). A total of five separate measuring periods were carried out during the storage period (14 November 1997–28 April 1998). Each measuring period ranged over 6–8 days. Measurements were made simultaneously on the two heaps. Four masts with passive flux samplers were used for each ammonia heap (Fig. 1). At the start of each measuring period, duplicate samplers were attached at four different heights on each mast. The passive flux samplers were attached at the following four heights:
Fig. 1. Principal arrangement for ammonia measurement with passive flux samplers; the horizontal outgoing and incoming fluxes of ammonia through the samplers are representative for vertical subareas surrounding the manure heap
457
046, 184, 460 and 800 m above ground surface. The sampler construction permits separate measurement of fluxes from both the ammonia source area and the background. At the end of a measuring period, the samplers were labelled and taken down for analysis. Ammonia nitrogen content in the samplers were detected by means of the indophenol blue method and spectrophotometric analysis (SIS, 1976). The total fluxes were then integrated, considering the vertical areas represented by the sampler positions. The net flux was then calculated as the total outgoing flux that leaves the ammonia source area reduced by the total incoming background flux. 2.2. Spreading Broiler manure from the uncovered storage and a commercial fertilizer product ‘Binadan’ (a mixture of broiler manure, harvest residues and stonemeal in the form of dry pellets) were spread on arable land. Ammonia emissions were measured from plots fertilized with broiler manure and pellets, respectively, with and without harrowing 4 h after spreading. 2.2.1. Site and experimental conditions The spreading experiment was located at Ultuna, 5 km south of Uppsala at 598490 N178390 E. The soil had a texture classified as clay (FAO, 1990) and 23% organic matter. The average air temperature for the years 1961–1990 was 588C and, on average, the total precipitation was 544 mm (H(arsmar, 1991). The treatments were arranged as a randomized block design with three replicates. Differences between treatments in the block experiment were analysed using a general linear model (GLM) in the statistic package of SAS 6.12 (SAS Institute Inc, 1994). 2.2.2. Application of manure The manure was spread on 28th May 1998, on a harrowed soil surface. The spreading rate was of 110 kg [total-N] ha1, corresponding to a rate of 44 t broiler manure per hectare and 27 t pellets per hectare. The broiler manure was applied with a spreader JF, type ST70-H, modified as a two-step spreader. The spreader was equipped with a regulation system as described by Carlson and Andersson (1990), in order to achieve a constant unloading rate along the bout. Pellets was applied with a pneumatic broadcaster, equipped with a 12 m spreading boom, where only half of the boom width was used. The lateral distribution when spreading broiler manure with the spreader JF, type ST70-H was measured according to the methodology described in CEN (1997). This test was performed at the Swedish
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Institute of Agricultural and Environmental Engineering (JTI) experimental test station (NMTI et al., 1994). The length of the plots was 10 m and the width of the plots was adjusted to the actual spreading width of the spreader (Figs 2 and 3). In each plot, two subplots 3 m wide were marked, one for no incorporation of manure, and the other for harrowing 4 h after spreading. For broiler manure, the subplots were placed on each side of the tracks such that measurements were taken in regions of the spreading zone, which received the correct
Plot:
Plot:
No incorporation
Harrowing 4 hours after spreading
3m
10 m
3m 20 m
Fig. 2. Diagram of plot layout for ammonia loss measurements from broiler manure
amount of applied fertilizer (Fig. 2). For pellets, the subplots were placed side by side on one side of the tracks (Fig. 3). 2.2.3. Ammonia emissions An equilibrium concentration method, developed at JTI, was used for measuring ammonia emissions (Svensson, 1994). The method is based on passive diffusion sampling close to the ground (Fig. 4). On each plot, measurements were carried out with two chambers to estimate the equilibrium concentration, and with one ambient measuring unit to estimate the ambient concentration of NH3. Number and length of sampling periods were adjusted to treatment. For plots fertilized with broiler manure with no incorporation, the NH3 emissions were measured on five occasions over a period of 5 days and for plots fertilized by broiler manure and harrowed 4 h after spreading on three occasions during 2 days. The pellet applied plots, with and without incorporation, were measured on two sampling periods. In one of the unfertilized plots, ammonia emissions were also measured during the first day. During the ammonia measurements, air temperature at 15 m height, soil surface temperature and wind speed at 2 m height were continuously recorded by means of a Vicon WS 801 weather station (Vicon Ltd., Ipswich, UK).
3. Results and discussion 3.1. Storing Plot :
Plot :
No incorporation
Harrowing 4 hours after spreading 10 m
3m
3m 8m
Fig. 3. Diagram of plot layout for ammonia loss measurements from dry pellets
Temperature measurements taken in the heaps indicated the presence of biological activity during storage (Fig. 5). The highest temperatures were recorded in the straw-covered heap. Thostrup (1985) concluded that a high temperature (70–808C) does not necessarily indicate a high composting rate. The population of microorganisms changes at different temperatures. However, the most efficient composting organisms were found by Thostrup (1985) to occur in the range 50–658C. Despite high temperatures, the amount of nitrogen lost in the form of ammonia was limited. Cumulative ammonia losses, as a percentage of the total nitrogen, were 7% from the uncovered heap and 10% from the heap with straw cover. The ammonia emission rates were highest during the first of the five measuring periods (Fig. 6). The main effects of the straw cover seem to have been insulation and rain protection. Cereal straw was chosen as a cover material because of its low price and ready availability on most Swedish farms. No reduction in ammonia emission was seen compared to
459
AMMONIA EMISSIONS FROM BROILER MANURE
24 V DC
Voltage controller Ventilated chamber
Wind shield
Ambient samplers
Fan Diffusional samplers Metal frame
Fig. 4. Experimental apparatus for measuring ammonia emissions after land spreading of manure
60
Temperature, °C
50 40 30 20 10 0 −10 1 Nov
1 Dec
1 Jan
1 Feb Date
1 Mar
1 Apr
Fig. 5. Ambient air temperature and mean temperatures recorded during storage in two broiler manure heaps, with and without cover: , heap without cover; , heap with straw cover; , ambient air 40 −1
35 30
3
−1
25 15 10 5 0
Nov
Dec
Jan Feb Mar Storage period, month
Apr
the uncovered heap. These nitrogen loss figures should be considered as minimum values since no data are available for the losses during the first week after mucking out. It is assumed that emissions during this period were limited, due to the fact that the manure was stored in containers which restricted oxygen availability and hence the degree of aerobic decomposition compared with storage in heaps. The properties of the broiler manure, at the start and end of storing, and the pellets used in the field experiment are presented in Table 2. After storage, there was a difference in dry matter content between the two heaps. In the uncovered heap, the dry matter content decreased, while in the covered heap the level remained the same as at the start. The bulk density was 590 kg m3 with a standard deviation (SD) of 137 kg m3 at the start. Corresponding figures at the end of storage were 610 kg m3 (SD of 552 kg m3) for the uncovered heap and 634 kg m3 (SD of 146 kg m3) for the straw-covered heap. During storage, biological activity led to a 27% decrease in the amount of dry matter, both in the covered and uncovered heaps. On a wet basis, the covered heap also decreased in weight by 30%. However, the uncovered heap had the same weight at the end of storage as it did at the start.
May
Fig. 6. Ammonia losses from two broiler manure heaps, with and without cover: , heap without cover; , heap with straw cover
3.2. Spreading Measurement of ammonia, after spreading uncovered broiler manure and pellets, continued for 5 days. During
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L. RODHE; S. KARLSSON
Table 2 Analysis of broiler manure, at the start and at the end of storing, and analysis of pellets used in the field experiment; analysis according to Swedish Standards Institute (SIS), Deutsches Institut fu¨r Normung e.V. (DIN), and American Public Health Association (APHA) Analysis
At the start of storing broiler manure
Dry matter, % pH Total-N, kg t1 NH4-N, kg t1 P, kg t1 K, kg t1 C/N
At the end of storing broiler manure
Dried pellets
Heap without cover*
Heap with straw cover
401 85 250 86 74 13 64
579 85 240 75 91 18 94
554 68 260 67 82 14 89
883 56 540 59 34 88 Not analysed
*
Used in spreading experiments.
Table 3 Application rate and nitrogen lost after spreading of dry pellets or stored broiler manure with no incorporation or incorporation 4 h after spreading Application method
Application rate kg [NH4-N] ha
Dried pelleted manure, no incorporation Dried pelleted manure, incorporated 4 h after spreading Stored broiler manure, no incorporation Stored broiler manure, incorporated 4 h after spreading
1
Nitrogen lost as ammonia 1
kg [Tot-N] ha
1
kg [N] ha
Percentage of NH4-N applied, %
Percentage of Tot-N applied, %
13
119
0
0
0
13
119
0
0
0
38
110
148
391
135
38
110
83
218
75
this period, the average air temperature was 1238C, the average surface temperature was 1638C and the average wind speed was 26 m s1. Some showers of rain occurred and the total precipitation was 304 mm for the period of ammonia measurement. It was found that 135% of the total nitrogen in the broiler manure was lost as ammonia after spreading without incorporation of the manure, and 75% was lost from plots with incorporation 4 h after spreading (Table 3). The difference in losses were not statistically significant (probability P 5 005). The losses after no incorporation are about the same as those measured by Chambers et al. (1997) in one of their experiments (Table 1). However, the field conditions in the experiment made by Chambers et al. (1997) and the experiment presented here differ in a variety of aspects, e.g. application rate and surface conditions. Figure 7 presents the cumulative losses of ammonia after spreading the broiler manure with and without incorporation. When the broiler manure was not
incorporated, half of the emission occurred within 4 h after spreading. After incorporation no ammonia emission occurred, and incorporation can be said to have been an effective measure in preventing further emissions. Malgeryd (1998) also concluded that incorporation was one of the most effective methods for reducing ammonia emissions after spreading. No emissions occurred from the plots fertilized with pellets. The low part of NH4-N of total-N, about 11%, together with the compressed form of dry manure could explain the low ammonia losses.
3.3. Total losses during handling The ammonia losses during storage from the uncovered broiler manure heap and the ammonia losses after spreading with and without incorporation are summarized in Fig. 8. The losses during 7 months of storage were of approximately the same magnitude as
461
AMMONIA EMISSIONS FROM BROILER MANURE
N released as NH3, kg [N] ha−1
20
15
10
5
0 0
10
20
30
40
50
60
70
80
90
100
110
120
130
Time h, after spreading
N released as NH3, % of total N
Fig. 7. Accumulated nitrogen losses as ammonia after spreading of broiler manure, 44 t h1, to arable land with and without incorporation of the manure 4 h after spreading: , no incorporation; , incorporation 4 h after spreading
25
Spreading without incorporation
20
Spreading with incorporation 4 hours after spreading
15 10 5 Storage 0 Nov
Dec
Jan
Mar Feb Month
Apr
May
June
Fig. 8. Accumulated nitrogen losses caused by ammonia emission during uncovered storage, and followed by spreading of broiler manure with and without incorporation of the manure 4 h after spreading: , no incorporation; , incorporation 4 h after spreading
during the first 4 h after spreading onto the land. When no incorporation of the manure was performed, the losses after spreading were about double the size of the losses during storage.
4. Conclusions Ammonia losses during storage of broiler manure were limited to 10% of the initial total nitrogen. Covering the broiler manure heap with straw did not decrease the ammonia losses during storage compared to no cover.
The straw cover acted as a barrier against precipitation, thus limiting wetting of the manure. Incorporation after spreading of broiler manure is an effective way to reduce ammonia emissions. The incorporation should be carried out as soon as possible after spreading, or at least not more than 4 h after spreading, to limit the ammonia losses to about half of the potential amount. Since no ammonia emissions were detected after spreading the dry pellets, no ammonia reducing measures are of current interest.
Acknowledgements Financial support by the Swedish Board of Agriculture is gratefully acknowledged.
References APHA (1985). Standard Methods (16th Edn.) 1985. American Public Health Association, St. Meth. 417A+d. Washington, DC, USA . (1990). Improvement of the perforCarlson G; Andersson O mance of the application rate for solid-manure spreaders. AgEng 90, Berlin CEN (1997). Manure spreaders } specification for environmental preservation } requirements and test methods. DRAFT prEN 13080. Comit!e Europ!een de Normalisation, Central Secretariat, rue de Stassart, 36 B-1050 Brussels Chambers B J; Smith K A; van der Weerden T J (1997). Ammonia emissions following the land spreading of solid manures. In: Nitrogen Emissions from Grasslands (Jarvis S C; Pain B F, eds), pp 275–280. CAB International, Oxon, UK
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DIN (1988). DIN 38406.E22. Bestimmung der 33 elemente Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, W, Zn und Zr durch Atomemissionsspektrometrie mit induktiv gekoppeltem Plasma [Determination of 33 elements Ag. . ...Zr by atom emissions spectrometry with inductive connected plasma] (ICP-OES). Deutsches Institut fu. r Normung e.V., Germany Elliot H A; Collins N E (1983). Chemical methods for controlling ammonia release from poultry manure. ASAE Paper No. 83–4521 FAO (1990). Guidelines for Soil Profile Description (3rd edn., revised) pp. 1–70. Food and Agriculture Organisation of the United Nations, Rome, Italy Groot Koerkamp P W G (1994). Review on emissions of ammonia from housing systems for laying hens in relation to sources, processes, building design and manure handling. Journal of Agricultural Engineering Research, 59, 73–87 H(arsmar P (1991). V.ader och vatten 1991 [Weather and water 1991]. The Swedish Meteorological and Hydrological Institute (SMHI), Norrko. ping, Sweden H.ornig G; T.urk M; Wanka U (1999). Slurry covers to reduce ammonia emission and odour nuisance. Journal of Agricultural Engineering Research, 73, 151–157, doi:10.1006/ jaer.1998.0402 Jeppsson K-H; Karlsson S; Svensson L; Beck-Friis B; Bergstr.om J (1997). Djupstro. b.add fo. r ungno. t och slaktsvin. [Deep litter for young cattle and growing-finishing pigs.] JBTrapport 110. Swedish University of Agricultural Sciences, Alnarp, Sweden Karlsson S (1994). Composting of deep straw manure. EurAgEng Paper No. 94-C-092, AgEng94 International Conference on Agricultural Engineering, Milano, Italy Kirchmann H (1985). Losses, plant uptake and utilisation of manure nitrogen during a production cycle. Acta Agriculturae Scandinavica (suppl. 24). The Scandinavian Association of Agricultural Scientists and the Royal Swedish Academy of Agriculture and Forestry, Uppsala, Sweden. Kirchmann H (1991). Carbon and nitrogen mineralization of fresh, aerobic and anareobic animal manures during incubation with soil. Swedish Journal of Agricultural Research, 21, 165–173 Kichmann H; Witter E (1992). Composition of fresh, aerobic and anaerobic farm animal dungs. Bioresource Technology, 40, 137–142 Kroodsma W; Scholtens R; Huis in’t Veld J (1988). Ammonia emission from poultry housing systems. In: Paper presented at the CIGR seminar on: Storing, Handling and Spreading of Manure and Municipal waste, 20–22 September 1988, Uppsala, Sweden Lockyer D R; Pain B F (1989). Ammonia emission from cattle, pig and poultry wastes applied to pasture. Environmental Pollution, 56, 19–30 Malgeryd J (1994). Manure characterization. International Agrophysics, 8(1), 93–101, Polish Academy of Sciences, Lublin
Malgeryd J (1998). Technical measures to reduce ammonia losses after spreading of animal manure. Nutrient Cycling in Agroecosystems, 51, 51–57 NMTI; JTI; SLU (1994). Technique and methods for the typetesting of fertiliser and manure spreaders. Final report from the Certification 93 programme. Swedish National Machinery Testing Institute, Uppsala, Sweden Puumala M (2001). Storage of manure in heaps. In: Sustainable Handling and Utilisation of Livestock Manure from Animals to Plants (Rom H B; Sorensen C G, eds). Proceedings of NJF Seminar no. 320, Denmark, 16–19 January 2001. DIAS report Animal Husbandry no. 21. Danish Institute of Agricultural Sciences, Tjele Rodhe L; Salomon E; Rammer C (1996). Spreading of farmyard manure to ley with different methods. Yield and silage quality. Swedish Journal of Agricultural Research, 26, 43–51 SAS Institute Inc (1994). SAS/STAT1 User’s Guide, Version 6, (4th Edn). Cary, NC, USA SCB (1998). Utsl.app till luft av ammoniak i Sverige 1997. [Release of ammonia in Sweden 1997.] Statistiska meddelanden Mi 37 SM 9901. Statistics Sweden, Stockholm, Sweden Schjørring J K; Sommer S G; Ferm M (1992). A simple passive sampler for measuring ammonia emission in the field. Water, Air, and Soil Pollution, 62, 13–24 SIS (1976). Swedish Standard: SIS 028134. Swedish Standards Institute, Stockholm, Sweden SIS (2000). Swedish standards: SS-EN 12176-1, SS 028113-1, SS 028101-1. Swedish Standards Institute, Stockholm, Sweden SJV (1998). Swedish statute-book. Swedish Board of Agriculture, SJVFS 1998:132 SLU (1997). Monthly report of meteorological observations. Oct–Dec, 1997. (In Swedish). Institutionen fo. r v.axtodling, Swedish University of Agricultural Sciences, Uppsala, Sweden SLU (1998). Monthly report of meteorological observations. Jan}May, 1998. (In Swedish). Institutionen fo. r v.axtodling, Swedish University of Agricultural Sciences, Uppsala, Sweden Sommer S G; Christensen B T; Nielsen N E; Schjørring J K (1993). Ammonia volatilization during storage of cattle and pig slurry: effect of surface cover. Journal of Agricultural Science, 121, 63–71 Svensson L (1994). A new dynamic chamber technique for measuring ammonia emissions from landspread manure and fertilisers. Acta Agriculturae Scandinavica, Section B, Soil and Plant Science, 44(1), 35–46 Thostrup P (1985). Heat recovery from composting solid manure. In: Composting of Agricultural and Other Wastes (Gasser JKR, ed.), Proceedings of a seminar organised by the Commission of the European Communities, Directorate-General Science, Research and Development, Environment Research Programme, held at Brasenose College, Oxford, UK, 19–20 March 1984. Elsevier Applied Science Publishers Ltd, London
Ammonia Emissions from Broiler Manure } Influence of Storage and Spreading Method Lena Rodhe; Stig Karlsson JTI } Swedish Institute of Agricultural and Environmental Engineering, P.O. Box 7033, S-750 07 Uppsala, Sweden; e-mail of corresponding author: [email protected] (Received 5 May 2001; accepted in revised form 12 April 2002; published online 11 July 2002)
Knowledge is poor concerning losses of ammonia from broiler manure during storage and after spreading. Broiler manure was stored from October to May in two separate heaps, one uncovered and one covered with a 30 cm layer of straw. Ammonia emissions were measured with a micrometeorological mass balance method in five separate periods during storage. Ambient air temperature and temperatures in the heaps were recorded continuously. After storage, broiler manure from the uncovered heap and commercial fertilizer pellets including broiler manure were spread to arable land at a rate of 110 kg [total-N] ha1. Ammonia emissions were measured with an equilibrium concentration method from plots fertilized with broiler manure and pellets, respectively, with and without harrowing 4 h after spreading. Temperature measurements taken in the heaps during storage indicated high biological activity. The highest temperatures were recorded in the strawcovered heap. Cumulative ammonia losses were 7% of total nitrogen from the uncovered heap and 10% from the heap with cover. Totally, 135% of the nitrogen in the broiler manure was lost as ammonia after spreading without incorporation of the manure and 75% from plots with incorporation. After incorporation no ammonia emission occurred. No emissions occurred from plots fertilized with pellets. # 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved
1. Introduction In Sweden, broiler manure is increasingly sold as commercial fertilizer with organic farming being the principal market. However, knowledge is poor about nutrient losses from broiler manure during storage and after spreading in crop production. Approximately 47 400 t [N] year1 are emitted from Swedish agriculture in the form of ammonia (SCB, 1998), corresponding to about 90% of the total amount of ammonia released in Sweden. Most of this nitrogen originates from manure and its loss not only contributes to eutrophication and acidification, but also represents a loss of a valuable plant macronutrient. In relation to fresh cattle and pig excreta, fresh poultry excreta have a high concentration of nitrogen (Kirchmann & Witter, 1992). Fresh faeces from poultry contains nitrogen in the form of uric acid (61%), organically bound nitrogen (31%) and ammonia (8%) (Kirchmann, 1991). After excretion, the uric acid and undigested proteins degrade, resulting in the formation 1537-5110/02/ $35.00
of ammonia, which can be lost by volatilization (Groot Koerkamp, 1994). The degradation processes are microbial mediated and require the presence of water and oxygen. According to Elliot and Collins (1983), the ammonia release is highest from manure with dry matter contents between 40 and 60%. Groot Koerkamp (1994) stated that the minimum ammonia emission from manure is achieved if a dry matter content of 60% is reached within 50 h after excretion of the faeces (this minimizes the degradation of uric acid and undigested proteins). Studies of stored broiler manure (Kroodsma et al., 1988) in a ventilated container unit showed a positive relationship between low NH3 emissions and dry manure. For moist broiler manure (55% DM), the spontaneous generation of heat tended to be short and considerable, whilst the accompanying NH3 emission was high at the start of storage period. Kirchmann (1985) showed a clear relationship between the initial C/N ratio and the magnitude of ammonia losses from poultry 455
# 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved
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manure stored under aerobic conditions. The study was performed as a laboratory incubation experiment with poultry manure and oat straw litter during aerobic and anaerobic conditions. Under anaerobic decomposition conditions, hardly any ammonia losses occurred, but during aerobic conditions the losses were high. The highest losses, 40% of the manure nitrogen, were achieved from the manure with the lowest C/N (18). Jeppsson et al. (1997) showed that the choice of bedding material in the livestock buildings could considerably influence the ammonia losses during storage of cattle manure. Only 2% of the nitrogen was lost as ammonia when peat and chopped straw were used as mixed litter compared to a 23% loss with untreated straw as litter. Puumala (2001) tested peat as a cover on a manure heap with broiler peat litter and measured temperatures, effluents and estimated ammonia losses. The temperatures in the covered heap declined more slowly than in the uncovered heap. The estimated ammonia losses were reduced by 80–90% when the peat cover was used compared to the uncovered heap. There is also evidence that straw, used as a surface cover, can reduce ammonia emissions from slurry storages (Sommer et al., 1993; Ho. rnig et al., 1999). Ammonia losses after spreading of broiler manure have been measured by Lockyer and Pain (1989) and Chambers et al. (1997), see Table 1. In all three experiments, the manure was applied to growing crops and the losses were between 7 and 14% of the total-N in the broiler manure. Measures to reduce ammonia emissions after spreading of solid manure on arable land have been studied by Malgeryd (1998). An effective way to reduce ammonia emissions is to incorporate the manure into the soil after spreading. By harrowing 4 h after spreading of solid manure on bare soil, emissions were reduced by almost 90% compared to the situation where no incorporation was made. Furthermore, animal manure spread on bare soil should be incorporated within 4 h in the southernmost regions of Sweden. This regulation was adopted in 1996 (SJV, 1998). Irrigation after spreading of solid manure is
another method which can reduce ammonia emissions (Rodhe et al., 1996). The aim of the work was to investigate how different handling methods of broiler manure affect ammonia emissions and manure properties. Measures compared were presence and absence of a straw cover during storage, and incorporation and non-incorporation of the surface spread manure.
2. Materials and methods 2.1. Storing The manure used, consisted of faeces from chickens (from 1-day old to about 5 weeks of age) and a bed of wood shavings placed in the broiler house at the start of the growing period. The broiler manure was removed from the stable, and temporarily stored in steel containers outside the broiler chicken house for about a week. Thereafter, it was transported to the experimental site located in the eastern part of the Svealand district of Sweden, at 598500 N178480 E. Here, the manure was studied during a storage period of 7 months, from the end of October until the end of May. The manure was placed in two separate heaps, one uncovered and one covered with a 30 cm layer of straw. Each heap was approximately 40 m wide at ground level, 110 m long and 11 m high. The mass of the uncovered heap was 15 300 kg, while the corresponding figure for the covered heap was 16 000 kg, straw cover excluded. A net was placed on top of the covered heap to ensure stability of the straw layer. Bulk density, dry matter content, pH and nutrient content of the manure were measured at the start and at the end of the storage period. For measuring bulk density, a specially made ‘characterization box’ was used (Malgeryd, 1994). The box held 13 m3 of manure and was handled and filled with a tractor-mounted front loader. Bulk density was measured by weighing the whole box for three samples per heap. Manure samples were taken for chemical
Table 1 Manure analysis, application rate, nitrogen losses as ammonia after spreading, and measuring period for three different broiler manures Dry matter, %
75 639 587 *
NH4 –N*, %
057 094 134
Tot-N, %
Rate, t ha1
295 311 305
Chambers et al. (1997) included uric acid-N.
60 69 99
N-losses % of NH4 -N
% of tot-N
372 46 15
72 14 7
Measuring period, days
References
6 9 23
Lockyer & Pain, (1989) Chambers et al., (1997) Chambers et al., (1997)
AMMONIA EMISSIONS FROM BROILER MANURE
analyses taken from the middle of each box with a pitchfork. One sample was taken when the box was half filled and one when it was completely filled. Standards from SIS (2000), DIN (1988) and APHA (1985) were used for analysing dry matter, pH and nutrient content. Ambient air temperature and heap temperatures were recorded continuously. Heap temperatures were measured at eight different locations in each heap. The precipitation during the storage period was 300 mm measured at Ultuna meteorological station situated 598490 N178480 E, about 10 km west of the experimental site (SLU, 1997, 1998). For measuring ammonia emissions, a micrometeorological mass balance method was used, described by Schjørring et al. (1992) and applied by Karlsson (1994). A total of five separate measuring periods were carried out during the storage period (14 November 1997–28 April 1998). Each measuring period ranged over 6–8 days. Measurements were made simultaneously on the two heaps. Four masts with passive flux samplers were used for each ammonia heap (Fig. 1). At the start of each measuring period, duplicate samplers were attached at four different heights on each mast. The passive flux samplers were attached at the following four heights:
Fig. 1. Principal arrangement for ammonia measurement with passive flux samplers; the horizontal outgoing and incoming fluxes of ammonia through the samplers are representative for vertical subareas surrounding the manure heap
457
046, 184, 460 and 800 m above ground surface. The sampler construction permits separate measurement of fluxes from both the ammonia source area and the background. At the end of a measuring period, the samplers were labelled and taken down for analysis. Ammonia nitrogen content in the samplers were detected by means of the indophenol blue method and spectrophotometric analysis (SIS, 1976). The total fluxes were then integrated, considering the vertical areas represented by the sampler positions. The net flux was then calculated as the total outgoing flux that leaves the ammonia source area reduced by the total incoming background flux. 2.2. Spreading Broiler manure from the uncovered storage and a commercial fertilizer product ‘Binadan’ (a mixture of broiler manure, harvest residues and stonemeal in the form of dry pellets) were spread on arable land. Ammonia emissions were measured from plots fertilized with broiler manure and pellets, respectively, with and without harrowing 4 h after spreading. 2.2.1. Site and experimental conditions The spreading experiment was located at Ultuna, 5 km south of Uppsala at 598490 N178390 E. The soil had a texture classified as clay (FAO, 1990) and 23% organic matter. The average air temperature for the years 1961–1990 was 588C and, on average, the total precipitation was 544 mm (H(arsmar, 1991). The treatments were arranged as a randomized block design with three replicates. Differences between treatments in the block experiment were analysed using a general linear model (GLM) in the statistic package of SAS 6.12 (SAS Institute Inc, 1994). 2.2.2. Application of manure The manure was spread on 28th May 1998, on a harrowed soil surface. The spreading rate was of 110 kg [total-N] ha1, corresponding to a rate of 44 t broiler manure per hectare and 27 t pellets per hectare. The broiler manure was applied with a spreader JF, type ST70-H, modified as a two-step spreader. The spreader was equipped with a regulation system as described by Carlson and Andersson (1990), in order to achieve a constant unloading rate along the bout. Pellets was applied with a pneumatic broadcaster, equipped with a 12 m spreading boom, where only half of the boom width was used. The lateral distribution when spreading broiler manure with the spreader JF, type ST70-H was measured according to the methodology described in CEN (1997). This test was performed at the Swedish
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Institute of Agricultural and Environmental Engineering (JTI) experimental test station (NMTI et al., 1994). The length of the plots was 10 m and the width of the plots was adjusted to the actual spreading width of the spreader (Figs 2 and 3). In each plot, two subplots 3 m wide were marked, one for no incorporation of manure, and the other for harrowing 4 h after spreading. For broiler manure, the subplots were placed on each side of the tracks such that measurements were taken in regions of the spreading zone, which received the correct
Plot:
Plot:
No incorporation
Harrowing 4 hours after spreading
3m
10 m
3m 20 m
Fig. 2. Diagram of plot layout for ammonia loss measurements from broiler manure
amount of applied fertilizer (Fig. 2). For pellets, the subplots were placed side by side on one side of the tracks (Fig. 3). 2.2.3. Ammonia emissions An equilibrium concentration method, developed at JTI, was used for measuring ammonia emissions (Svensson, 1994). The method is based on passive diffusion sampling close to the ground (Fig. 4). On each plot, measurements were carried out with two chambers to estimate the equilibrium concentration, and with one ambient measuring unit to estimate the ambient concentration of NH3. Number and length of sampling periods were adjusted to treatment. For plots fertilized with broiler manure with no incorporation, the NH3 emissions were measured on five occasions over a period of 5 days and for plots fertilized by broiler manure and harrowed 4 h after spreading on three occasions during 2 days. The pellet applied plots, with and without incorporation, were measured on two sampling periods. In one of the unfertilized plots, ammonia emissions were also measured during the first day. During the ammonia measurements, air temperature at 15 m height, soil surface temperature and wind speed at 2 m height were continuously recorded by means of a Vicon WS 801 weather station (Vicon Ltd., Ipswich, UK).
3. Results and discussion 3.1. Storing Plot :
Plot :
No incorporation
Harrowing 4 hours after spreading 10 m
3m
3m 8m
Fig. 3. Diagram of plot layout for ammonia loss measurements from dry pellets
Temperature measurements taken in the heaps indicated the presence of biological activity during storage (Fig. 5). The highest temperatures were recorded in the straw-covered heap. Thostrup (1985) concluded that a high temperature (70–808C) does not necessarily indicate a high composting rate. The population of microorganisms changes at different temperatures. However, the most efficient composting organisms were found by Thostrup (1985) to occur in the range 50–658C. Despite high temperatures, the amount of nitrogen lost in the form of ammonia was limited. Cumulative ammonia losses, as a percentage of the total nitrogen, were 7% from the uncovered heap and 10% from the heap with straw cover. The ammonia emission rates were highest during the first of the five measuring periods (Fig. 6). The main effects of the straw cover seem to have been insulation and rain protection. Cereal straw was chosen as a cover material because of its low price and ready availability on most Swedish farms. No reduction in ammonia emission was seen compared to
459
AMMONIA EMISSIONS FROM BROILER MANURE
24 V DC
Voltage controller Ventilated chamber
Wind shield
Ambient samplers
Fan Diffusional samplers Metal frame
Fig. 4. Experimental apparatus for measuring ammonia emissions after land spreading of manure
60
Temperature, °C
50 40 30 20 10 0 −10 1 Nov
1 Dec
1 Jan
1 Feb Date
1 Mar
1 Apr
Fig. 5. Ambient air temperature and mean temperatures recorded during storage in two broiler manure heaps, with and without cover: , heap without cover; , heap with straw cover; , ambient air 40 −1
35 30
3
−1
25 15 10 5 0
Nov
Dec
Jan Feb Mar Storage period, month
Apr
the uncovered heap. These nitrogen loss figures should be considered as minimum values since no data are available for the losses during the first week after mucking out. It is assumed that emissions during this period were limited, due to the fact that the manure was stored in containers which restricted oxygen availability and hence the degree of aerobic decomposition compared with storage in heaps. The properties of the broiler manure, at the start and end of storing, and the pellets used in the field experiment are presented in Table 2. After storage, there was a difference in dry matter content between the two heaps. In the uncovered heap, the dry matter content decreased, while in the covered heap the level remained the same as at the start. The bulk density was 590 kg m3 with a standard deviation (SD) of 137 kg m3 at the start. Corresponding figures at the end of storage were 610 kg m3 (SD of 552 kg m3) for the uncovered heap and 634 kg m3 (SD of 146 kg m3) for the straw-covered heap. During storage, biological activity led to a 27% decrease in the amount of dry matter, both in the covered and uncovered heaps. On a wet basis, the covered heap also decreased in weight by 30%. However, the uncovered heap had the same weight at the end of storage as it did at the start.
May
Fig. 6. Ammonia losses from two broiler manure heaps, with and without cover: , heap without cover; , heap with straw cover
3.2. Spreading Measurement of ammonia, after spreading uncovered broiler manure and pellets, continued for 5 days. During
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Table 2 Analysis of broiler manure, at the start and at the end of storing, and analysis of pellets used in the field experiment; analysis according to Swedish Standards Institute (SIS), Deutsches Institut fu¨r Normung e.V. (DIN), and American Public Health Association (APHA) Analysis
At the start of storing broiler manure
Dry matter, % pH Total-N, kg t1 NH4-N, kg t1 P, kg t1 K, kg t1 C/N
At the end of storing broiler manure
Dried pellets
Heap without cover*
Heap with straw cover
401 85 250 86 74 13 64
579 85 240 75 91 18 94
554 68 260 67 82 14 89
883 56 540 59 34 88 Not analysed
*
Used in spreading experiments.
Table 3 Application rate and nitrogen lost after spreading of dry pellets or stored broiler manure with no incorporation or incorporation 4 h after spreading Application method
Application rate kg [NH4-N] ha
Dried pelleted manure, no incorporation Dried pelleted manure, incorporated 4 h after spreading Stored broiler manure, no incorporation Stored broiler manure, incorporated 4 h after spreading
1
Nitrogen lost as ammonia 1
kg [Tot-N] ha
1
kg [N] ha
Percentage of NH4-N applied, %
Percentage of Tot-N applied, %
13
119
0
0
0
13
119
0
0
0
38
110
148
391
135
38
110
83
218
75
this period, the average air temperature was 1238C, the average surface temperature was 1638C and the average wind speed was 26 m s1. Some showers of rain occurred and the total precipitation was 304 mm for the period of ammonia measurement. It was found that 135% of the total nitrogen in the broiler manure was lost as ammonia after spreading without incorporation of the manure, and 75% was lost from plots with incorporation 4 h after spreading (Table 3). The difference in losses were not statistically significant (probability P 5 005). The losses after no incorporation are about the same as those measured by Chambers et al. (1997) in one of their experiments (Table 1). However, the field conditions in the experiment made by Chambers et al. (1997) and the experiment presented here differ in a variety of aspects, e.g. application rate and surface conditions. Figure 7 presents the cumulative losses of ammonia after spreading the broiler manure with and without incorporation. When the broiler manure was not
incorporated, half of the emission occurred within 4 h after spreading. After incorporation no ammonia emission occurred, and incorporation can be said to have been an effective measure in preventing further emissions. Malgeryd (1998) also concluded that incorporation was one of the most effective methods for reducing ammonia emissions after spreading. No emissions occurred from the plots fertilized with pellets. The low part of NH4-N of total-N, about 11%, together with the compressed form of dry manure could explain the low ammonia losses.
3.3. Total losses during handling The ammonia losses during storage from the uncovered broiler manure heap and the ammonia losses after spreading with and without incorporation are summarized in Fig. 8. The losses during 7 months of storage were of approximately the same magnitude as
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AMMONIA EMISSIONS FROM BROILER MANURE
N released as NH3, kg [N] ha−1
20
15
10
5
0 0
10
20
30
40
50
60
70
80
90
100
110
120
130
Time h, after spreading
N released as NH3, % of total N
Fig. 7. Accumulated nitrogen losses as ammonia after spreading of broiler manure, 44 t h1, to arable land with and without incorporation of the manure 4 h after spreading: , no incorporation; , incorporation 4 h after spreading
25
Spreading without incorporation
20
Spreading with incorporation 4 hours after spreading
15 10 5 Storage 0 Nov
Dec
Jan
Mar Feb Month
Apr
May
June
Fig. 8. Accumulated nitrogen losses caused by ammonia emission during uncovered storage, and followed by spreading of broiler manure with and without incorporation of the manure 4 h after spreading: , no incorporation; , incorporation 4 h after spreading
during the first 4 h after spreading onto the land. When no incorporation of the manure was performed, the losses after spreading were about double the size of the losses during storage.
4. Conclusions Ammonia losses during storage of broiler manure were limited to 10% of the initial total nitrogen. Covering the broiler manure heap with straw did not decrease the ammonia losses during storage compared to no cover.
The straw cover acted as a barrier against precipitation, thus limiting wetting of the manure. Incorporation after spreading of broiler manure is an effective way to reduce ammonia emissions. The incorporation should be carried out as soon as possible after spreading, or at least not more than 4 h after spreading, to limit the ammonia losses to about half of the potential amount. Since no ammonia emissions were detected after spreading the dry pellets, no ammonia reducing measures are of current interest.
Acknowledgements Financial support by the Swedish Board of Agriculture is gratefully acknowledged.
References APHA (1985). Standard Methods (16th Edn.) 1985. American Public Health Association, St. Meth. 417A+d. Washington, DC, USA . (1990). Improvement of the perforCarlson G; Andersson O mance of the application rate for solid-manure spreaders. AgEng 90, Berlin CEN (1997). Manure spreaders } specification for environmental preservation } requirements and test methods. DRAFT prEN 13080. Comit!e Europ!een de Normalisation, Central Secretariat, rue de Stassart, 36 B-1050 Brussels Chambers B J; Smith K A; van der Weerden T J (1997). Ammonia emissions following the land spreading of solid manures. In: Nitrogen Emissions from Grasslands (Jarvis S C; Pain B F, eds), pp 275–280. CAB International, Oxon, UK
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DIN (1988). DIN 38406.E22. Bestimmung der 33 elemente Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, W, Zn und Zr durch Atomemissionsspektrometrie mit induktiv gekoppeltem Plasma [Determination of 33 elements Ag. . ...Zr by atom emissions spectrometry with inductive connected plasma] (ICP-OES). Deutsches Institut fu. r Normung e.V., Germany Elliot H A; Collins N E (1983). Chemical methods for controlling ammonia release from poultry manure. ASAE Paper No. 83–4521 FAO (1990). Guidelines for Soil Profile Description (3rd edn., revised) pp. 1–70. Food and Agriculture Organisation of the United Nations, Rome, Italy Groot Koerkamp P W G (1994). Review on emissions of ammonia from housing systems for laying hens in relation to sources, processes, building design and manure handling. Journal of Agricultural Engineering Research, 59, 73–87 H(arsmar P (1991). V.ader och vatten 1991 [Weather and water 1991]. The Swedish Meteorological and Hydrological Institute (SMHI), Norrko. ping, Sweden H.ornig G; T.urk M; Wanka U (1999). Slurry covers to reduce ammonia emission and odour nuisance. Journal of Agricultural Engineering Research, 73, 151–157, doi:10.1006/ jaer.1998.0402 Jeppsson K-H; Karlsson S; Svensson L; Beck-Friis B; Bergstr.om J (1997). Djupstro. b.add fo. r ungno. t och slaktsvin. [Deep litter for young cattle and growing-finishing pigs.] JBTrapport 110. Swedish University of Agricultural Sciences, Alnarp, Sweden Karlsson S (1994). Composting of deep straw manure. EurAgEng Paper No. 94-C-092, AgEng94 International Conference on Agricultural Engineering, Milano, Italy Kirchmann H (1985). Losses, plant uptake and utilisation of manure nitrogen during a production cycle. Acta Agriculturae Scandinavica (suppl. 24). The Scandinavian Association of Agricultural Scientists and the Royal Swedish Academy of Agriculture and Forestry, Uppsala, Sweden. Kirchmann H (1991). Carbon and nitrogen mineralization of fresh, aerobic and anareobic animal manures during incubation with soil. Swedish Journal of Agricultural Research, 21, 165–173 Kichmann H; Witter E (1992). Composition of fresh, aerobic and anaerobic farm animal dungs. Bioresource Technology, 40, 137–142 Kroodsma W; Scholtens R; Huis in’t Veld J (1988). Ammonia emission from poultry housing systems. In: Paper presented at the CIGR seminar on: Storing, Handling and Spreading of Manure and Municipal waste, 20–22 September 1988, Uppsala, Sweden Lockyer D R; Pain B F (1989). Ammonia emission from cattle, pig and poultry wastes applied to pasture. Environmental Pollution, 56, 19–30 Malgeryd J (1994). Manure characterization. International Agrophysics, 8(1), 93–101, Polish Academy of Sciences, Lublin
Malgeryd J (1998). Technical measures to reduce ammonia losses after spreading of animal manure. Nutrient Cycling in Agroecosystems, 51, 51–57 NMTI; JTI; SLU (1994). Technique and methods for the typetesting of fertiliser and manure spreaders. Final report from the Certification 93 programme. Swedish National Machinery Testing Institute, Uppsala, Sweden Puumala M (2001). Storage of manure in heaps. In: Sustainable Handling and Utilisation of Livestock Manure from Animals to Plants (Rom H B; Sorensen C G, eds). Proceedings of NJF Seminar no. 320, Denmark, 16–19 January 2001. DIAS report Animal Husbandry no. 21. Danish Institute of Agricultural Sciences, Tjele Rodhe L; Salomon E; Rammer C (1996). Spreading of farmyard manure to ley with different methods. Yield and silage quality. Swedish Journal of Agricultural Research, 26, 43–51 SAS Institute Inc (1994). SAS/STAT1 User’s Guide, Version 6, (4th Edn). Cary, NC, USA SCB (1998). Utsl.app till luft av ammoniak i Sverige 1997. [Release of ammonia in Sweden 1997.] Statistiska meddelanden Mi 37 SM 9901. Statistics Sweden, Stockholm, Sweden Schjørring J K; Sommer S G; Ferm M (1992). A simple passive sampler for measuring ammonia emission in the field. Water, Air, and Soil Pollution, 62, 13–24 SIS (1976). Swedish Standard: SIS 028134. Swedish Standards Institute, Stockholm, Sweden SIS (2000). Swedish standards: SS-EN 12176-1, SS 028113-1, SS 028101-1. Swedish Standards Institute, Stockholm, Sweden SJV (1998). Swedish statute-book. Swedish Board of Agriculture, SJVFS 1998:132 SLU (1997). Monthly report of meteorological observations. Oct–Dec, 1997. (In Swedish). Institutionen fo. r v.axtodling, Swedish University of Agricultural Sciences, Uppsala, Sweden SLU (1998). Monthly report of meteorological observations. Jan}May, 1998. (In Swedish). Institutionen fo. r v.axtodling, Swedish University of Agricultural Sciences, Uppsala, Sweden Sommer S G; Christensen B T; Nielsen N E; Schjørring J K (1993). Ammonia volatilization during storage of cattle and pig slurry: effect of surface cover. Journal of Agricultural Science, 121, 63–71 Svensson L (1994). A new dynamic chamber technique for measuring ammonia emissions from landspread manure and fertilisers. Acta Agriculturae Scandinavica, Section B, Soil and Plant Science, 44(1), 35–46 Thostrup P (1985). Heat recovery from composting solid manure. In: Composting of Agricultural and Other Wastes (Gasser JKR, ed.), Proceedings of a seminar organised by the Commission of the European Communities, Directorate-General Science, Research and Development, Environment Research Programme, held at Brasenose College, Oxford, UK, 19–20 March 1984. Elsevier Applied Science Publishers Ltd, London