A survey of the production and use of animal manures in England and Wales

Abstract. A survey of manure management practice was undertaken in 1996, by postal questionnaire submitted to a stratified sample of egg and broiler producers in England and Wales. Out of a target of 500 laying hen and 500 broiler (chickens produced for meat) production units in the survey sample, 356 (36%) returned questionnaires. The survey provided information on amount and type of manure production, manure storage and land application strategies (timing, techniques and awareness of nutrient content). Within the survey, no attempt was made to differentiate between organic and conventional production systems. About 45% of manure production was estimated to come from layer holdings, 55% from broiler litter. It was estimated that 70% of the national manure production is litter‐based and about 30% are droppings collected without litter. Sawdust/shavings are the most popular bedding material, with an average final depth of 100 mm for broilers and 140 mm on litter‐based layer units. Commonly, storage is available within housing for at least the length of the cropping cycle (6 weeks in broiler production, or 12 months in deep pit laying houses), around 60% of poultry manure is stored for a period following removal from the house, most commonly for 3‐6 months. Overall, autumn was the peak period for manure spreading, with over 40% of laying hen manure and 50% of broiler manure applied at that time. On grassland, spreading was reasonably evenly distributed throughout the year but autumn application was favoured for arable crops, especially before the establishment of cereals and root crops, overall, almost 50% of layer and broiler manure was applied in the autumn. In the survey, up to 10% of manures were claimed to be incorporated within a day of application and about 60% within a week of application, presumably because of concern about odour nuisance. Around 25% of poultry manure was applied by contractors. A high proportion of farmers (c. 40% with layers, c. 60% with broilers) exported manures from their holdings, the proportion removed amounting to almost 90% on these farms. Although evidence elsewhere indicates that farmers make little allowance for manures in planning crop fertilizer inputs, the survey responses suggested that farmers do make an effort to allow for manures but that their confidence in the advice available to them is lacking, or they may have other technical reasons for not taking advantage of the manurial value. Information provided by the survey is of significant importance to policy makers (e.g. for the construction of environmental emissions inventories), researchers, consultants and farmers.     

Yellow melon yield in response to mineral or organic fertilization

Although current recommendations in Brazil suggest the application of mineral and organic fertilizers, there is little information regarding the interaction between them in melon plants. This study aimed to evaluate the effects of mineral and organic fertilization in the plant development, nutritional status, and fruit yield of yellow melon. The following fertilizations were evaluated: mineral fertilization; bovine manure; bovine manure associated with mineral fertilization; poultry litter; and poultry litter associated with mineral fertilization. Bovine manure and poultry litter were applied at rates equivalent to 15 m³ ha^?1 and 5 m³ ha^?1, respectively. Phosphorus and potassium were applied based on the results of the soil analysis and nitrogen based on the expected yield of 20 to 30 t ha^?1 of fruits. Phosphate and organic fertilizers were applied at the time of preparation of the beds, while nitrogen and potassium were supplied daily through irrigation water. Goldex F1 melon hybrid seedlings were used in the experiment. Plants were collected to evaluate the dry matter production at beginning of flowering, beginning of fruiting, fruit growth, and fruit harvest. Leaves were collected at flowering stage to evaluate the nutritional status of plants. Harvest was made when the fruits reached the intense yellow coloration. Organic fertilizers alone and combined to mineral fertilizer did not affect the dry matter yield of leaves, stems, fruits and shoot, the concentrations of macro and micronutrients in melon leaves, the nitrogen accumulation in the plant, and the yield of the yellow melon. The application of bovine manure associated to mineral fertilization showed the lowest values of nitrogen recovery applied. Bovine manure application resulted in increase of nitrogen organic forms in soil.     

Agronomic Evaluation of Manure Ashes: Changes in Soil Phosphorus Fractions,Maize (Zea mays) Yield,and Phosphorus Uptake

ABSTRACT

In order to reduce bulkiness and concentrate its nutrients, manures were burnt to ashes, and the effect of manures and their ashes on soil phosphorus fractions and maize performance in laboratory incubation, screenhouse, and field experiments was evaluated. Treatments were control, dried poultry manure (DPM), poultry manure ash, dried cattle manure (DCM), cattle manure ash (CMA), dried goat manure, goat manure ash and NPK 15-15-15, each applied at 120 kg P ha^?1. Periodic data were taken from soil P fractions, maize yield, and P uptake. Results showed that manures and their ashes increased soil P fractions in incubation, screenhouse, and field experiments. Available P and Ca-P increased with application of DPM while CMA only increased labile P, Al-P, and Fe-P at later weeks. Dry matter yield and P uptake increased with the application of manures and ashes while available P was positively correlated with P uptake. The impact of manure ashes was comparable to manures, hence recommended for use as alternatives, thereby getting rid of the problems of manure bulkiness and offensive odors.     

Effects of seaweed and different farm manures on growth and yield of organic carrots

This study was carried out randomized complete blocks design with three replications during the growing seasons of 2010 and 2011 to compare the effects of conventional and organic production systems on yield, quality, and plant characteristics of Nantindo determinate carrot cultivar. In our study cow manure, sheep manure, poultry manure, seaweed, and conventional applications were made. As for average yield, the five-ton poultry manure application was the highest (5.91 t/ha^?1) whereas control application was the lowest (3.37 t/ha^?1). The widest root diameter, longest root length, the highest root weight, total soluble solids content, total sugar content, antioxidant activity were determined in different doses of poultry manure applications. A correlation between the examined quality and plant characteristics was determined. The other the most dry matter (11.80%), phenolic matter (188.98 mg.10^?2g^?1 GAE) and β carotene (205.95 µg.g^?1) contents was determined in conventional application. The different doses poultry manure application on growth and yield of carrot were determined a positive effect.     

Nitrate,nutrient content and growth parameters of komatsuna (Brassica rapa L.) in response to manure application depending on EMN (estimated mineralizable nitrogen)

We investigated the effects of poultry manures (PM) and cow manures (CM) using estimated mineralizable nitrogen (EMN) method on nitrate, nutrient content and growth parameters of komatsuna and compared with chemical fertilizer (CF) in an abandoned soil. We applied manures as EMN based on their total N content. The 100% of EMN by PM or CM enhanced dry matter (DM) but depressed nitrate content. The PM-Keifun (PMK) with total N (4.87%) produced greater growth parameters, DM, nutrient content and lower nitrate content but manures with total N (<2%) could not. The solo CF₁₅₀ did not promote leaf number but increased nitrate and Na content. In conclusion, a higher total N (>4%) concentration of manure led to increase availability and nutrient contents, DM, and depressed nitrate content of komatsuna, comparable with solo CF in an abandoned soil.     

Influence of different mulch treatments on growth rate and activity of the earthworm Eudrilus eugeniae (Kinberg)

Growth characteristics of the earthworm Eudrilus eugeniae and the impac of its activity on soil properties were studied in soil culture. The highest growth rate, fecundity and total weight increase were recorded in cassava mulch, compared with cocoyam mulch, grass and plantain pseudo trunk mulch treatments. With animal manure treatments, growth rate was highest in poultry manure compared with cow and goat manures although total weight increases were highest in poultry and goat manures and lowest in cow manure. The worm activity expressed as percentage reduction of soil bulk density was greatest in cassava mulch followed by grass mulch, cocoyam mulch and plantain pseudo trunk mulch in that order. Various animal manures did not differ in this aspect. Total soil N and soil organic matter increased significantly in cassava and grass mulch treatmens while in plantain pseudo trunk mulch these factors decreased. Soil pH increased in cocoyam and plantain mulch treatments and decreased in cassava and grass mulch treatments.     

Near-infrared diffuse reflectance spectroscopy for the analysis of poultry manures

The objective was to evaluate near-infrared diffuse reflectance spectroscopy (NIRS) for determining the composition of poultry manures. Poultry manure samples were obtained from a commercial testing laboratory along with conventionally determined analyte values for total N, NH(4)(+)-N, organic N (computed as total minus NH(4)(+)-N), minerals, and moisture. Samples were blended in a food blender and scanned in polyethylene bags on a FOSS-NIRSystems model 6500 scanning monochromator. Initial results indicated that changes had occurred in NH(4)(+)-N contents from the time of analysis, and samples were reanalyzed for NH(4)(+)-N. Using the new analyses, NIRS was able to accurately determine NH(4)(+)-N, organic N, total N, and moisture in 128 poultry manures. Results were more accurate when determinations were made on an "as is" as opposed to dry matter basis. Finally, results indicated that NIRS was not suitable for the determination of minerals (P, K, Ca, etc.) in poultry manures.     

Effect of Poultry Manure on Yield and Nutrient Composition of Sweet Basil (Ocimum basilicum L.)

Poultry manure is one of the best organic fertilizers available and is an extremely valuable resource, organic matter content, exchangeable cations, cation exchange capacity, and percent base saturation. Ocimum basilicum L. (sweet basil) is an essential oil producing crop used in culinary and fragrance applications. The objective of this present study was to evaluate the effects of organic poultry manure and conventional fertilization on plant growth, yield and inorganic matter content of sweet basil. In this context, the different doses of chicken and turkey manure (7.5, 10, 12.5, 15 t ha^?1) with a control (no manure) and conventional fertilization were applied with sowing. The highest fresh and dry weights were obtained from the plants grown with turkey and chicken manure at a rate of 10–12.5 t ha^?1. The most of the nutrient content varied significantly with organic poultry manure applications. Overall, basil plants fertilized with turkey manure at a rate of 10–12.5 t ha^?1 and 7.5 t ha^?1 chicken manure dose accumulated greater concentrations of potassium (K) and magnesium (Mg). The results from this study demonstrated that organic or conventional fertilizer can alter fresh or dry weight, and the nutrient content.     

Impact of Animal Manure on Soil Chemistry,Mineral Nutrients,Yield, and Fruit Quality in ‘Golden Delicious’ Apple

ABSTRACT

Incorporating deep litter cow and deep litter poultry manures with the top 30-cm soil improved orchard soil chemistry, including nutrient availability, soil organic matter, electrical conductivity (EC), pH, cation exchange capacity (CEC) and biological activity in a ‘Golden Delicious’ apple (Malus domestica Bork) orchard in Zanjan, Iran. Application of deep litter cow manure at 30 t ha^?1 or deep litter poultry manure at 10 t ha^?1 resulted in a higher rate of nitrogen (N) release, and thus increased yield and fruit size, but decreased fruit color. The least leaf minerals were found in the untreated control trees. The control trees showed minor symptoms of N, iron (Fe), and magnesium (Mg) deficiencies during the following season. Positive correlation existed between the rate of manure applied and the content of soil organic matter (OM). The deep litter poultry manure at 10 t ha^?1 increased the soil K, Mg, calcium (Ca), ammonium-N, and EC levels.     

Developing an Environmental Manure Test for the Phosphorus Index

Abstract

Widespread implementation of the phosphorus (P) index has focused attention on environmental manure tests that can be used to estimate the relative availability of P in manure to runoff water. This article describes the development and use of a water extractable P (WEP) test to assess the capacity of land‐applied manure to enrich P in runoff water. WEP of surface‐applied manure has been shown to be strongly correlated to dissolved P concentrations in runoff from agricultural soils. WEP tests that have a defined water‐to‐manure‐solids ratio and involve extraction times of 30 to 120 min provide the best prediction of dissolved P in runoff across a wide range of manures. Consistent measurement of manure WEP can be achieved with manure sample storage times of up to 22 days (4°C), acidified extract holding times of 18 days, and solid separation by either centrifugation or paper filtration. Reproducibility of WEP tests is comparable to that of other common manure tests (e.g., total P), as verified by within‐laboratory and inter laboratory evaluations. A survey of 140 livestock manures revealed significant differences in mean WEP among different livestock manures, with swine greater than poultry (turkey, broiler and layer chickens) and dairy cattle greater than beef cattle. Such results support the use of WEP‐based coefficients to modify the source component of the P index.     

Nitrogen Mineralization as Influenced by Different Organic Manures in an Inceptisol in the Foothill Himalayas

Nitrogen-use efficiency can be enhanced through an understanding of the nitrogen (N) mineralization behavior of organic sources. An incubation study was conducted to assess the impact of organic manures on N mineralization. The manures, farmyard manure (FYM), Leucaena leucocephala, and poultry manure, were applied to the soil alone or along with urea. There was a rapid increase in the amount of mineral N released with a peak appearing either at 14 days (+urea treatments) or 21 days (manure only) of aerobic incubation. Thereafter the net N mineralized decreased gradually and levelled off beyond day 56. Overall the cumulative net N mineralized after 98 days of incubation was in the order urea > Leucaena + urea > poultry manure + urea _> FYM + urea > Leucaena > poultry manure > FYM > zero N. The potentially mineralizable N (N₀) was lower in treatments where urea was not applied.     

Plant‐based fertilizers for organic vegetable production

To ensure high yield and quality in organic vegetable production, crops often require additional fertilizer applied during the season. Due to the risk of contamination of edible plant products from slurry, plant‐based fertilizers may be used as an alternative. The purpose of our work was to develop mobile green manures with specific high nutrient concentrations (e.g., nitrogen [N], sulfur [S], and phosphorus [P]) that are released quickly after soil incorporation and that are easy to handle during storage and application. To distinguish from traditional green manures that are grown to improve soil fertility, the term “mobile green manures” is used for green‐manure crops that are harvested in one field and then moved as a whole and used as fertilizer in other fields. To further investigate mobile‐green‐manure crops for use as efficient fertilizers, pot and field experiments were conducted with cauliflower (Brassica oleracea botrytis) and kale (Brassica oleracea sabellica) supplied with organic matter consisting of a wide range of plant species with varying nutrient concentrations. Further, field experiments were conducted with leek (Allium porrum) and celery (Apium graveolens dulce) supplied with increasing amounts of organic matter consisting of fresh, ensiled, or dried green manures. Results show that garden sorrel (Rumex acetosa), dyer's woad (Isatis tinctoria), and fodder radish (Raphanus sativus) harvested with a high leaf‐to‐stem ratio resulted in high P concentration, and cruciferous crops in high S concentration. Dyer's woad, salad burnet (Sanguisorba minor), and stinging nettle (Urtica dioica) showed high boron (B) concentration, whereas species such as dandelion (Taraxacum officinale), chicory (Cichorium intybus), and garden sorrel showed high potassium (K) concentration. Green manures with high P and S concentrations increased the nutrient uptake and yield of pot‐grown cauliflower and kale. Field experiments showed that the production of cauliflower and kale decreased when the carbon‐to‐nitrogen (C : N) ratio of applied green manure increased. In kale, for example, application of 160 kg N ha^–1 in early harvested lucerne (Medicago sativa) with a C : N ratio of 10 resulted in the highest kale production whereas application of an equal amount of N in late harvested lucerne with a C : N ratio of 20 produced 34% less. Differences in vegetable production were not due to the amount of N applied, but to the N availability. Field experiments with fresh, ensiled, or dry green manure applied to leek and celery showed that the C : N ratio has to be low to get a fast response. Further, these field experiments demonstrate the importance of green manures, which can be stored and are easy to handle during transport, crop application, and soil incorporation. It is concluded that it is possible to produce green manures with high concentrations of S, P, K, and B, and low C : N ratios and that these properties have a great impact on the value of the green manure for vegetable production.     

稻草与生石灰对设施土壤微量元素含量和番茄产量的影响

为了探究设施内添加稻草与生石灰对土壤微量元素含量和番茄产量的影响,以长期施肥定位试验为依托,比较了施用鸡粪(M)的基础上,添加稻草(MR)、生石灰(MCa)、稻草与生石灰同时添加(MRCa)各处理全土及各粒级团聚体中有效态Fe、Mn、Cu、Zn含量和番茄产量的变化。结果表明:(1)添加稻草可增加土壤中有效态Fe、Mn、Zn含量,MR处理较M处理分别增加3.2%,80.9%,15.1%,对有效态Cu含量无显著影响;添加生石灰也可增加土壤中微量元素含量,其中Mn含量增加显著。土壤中有效态Fe、Mn、Cn、Zn含量与pH呈极显著负相关(P<0.01),与有机质含量呈极显著正相关(P<0.01)。(2)随着土壤团聚体粒级的减小,有效态微量元素含量呈下降趋势。添加稻草和生石灰可增加1~0.25mm粒级中有效态Mn含量,MRCa处理较其他处理增加6.6%~46.6%;添加稻草可增加<0.25mm粒级中有效态Zn含量。土壤中有效态Fe含量与<1mm粒级中含量呈显著正相关(P<0.01);土壤中有效态Mn、Zn含量分别与各粒级中含量呈显著正相关(P<0.01);土壤中有效态Cu含量与1~0.25mm粒级中含量呈显著正相关(P<0.01)。(3)施入稻草或生石灰可增加番茄产量,且稻草和生石灰同时施入产量最高,MRCa处理较MCa、MR处理分别增加12.6%,33.8%。土壤有效态Fe、Cu含量与产量正相关,其中有效态Fe含量对产量具有直接作用,决策系数最高,土壤有效态Cu含量对产量具有间接作用。因此,可以通过长期添加稻草和适量生石灰缓解设施土壤微量元素短缺的现状,且可获得最高作物产量,为设施内土壤可持续利用和设施农业可持续发展提供保障。     

Mineralization and denitrification in upland, nearly saturated and flooded subtropical soil II. Effect of organic manures varying in N content and C:N ratio

 Nitrogen and carbon mineralization of cattle manure (N=6 g kg^–1; C:N=35), pressmud (N=17.4 g kg^–1; C:N=22), green manure (N=26.8 g kg^–1; C:N=14) and poultry manure (N=19.5 g kg^–1; C:N=12) and their influence on gaseous N losses via denitrification (using the acetylene inhibition technique) in a semiarid subtropical soil (Typic Ustochrepts) were investigated in a growth chamber simulating upland, nearly saturated, and flooded conditions. Mineralization of N started quickly in all manures, except pressmud where immobilization of soil mineral N was observed for an initial 4 days. Accumulation of mineral N in upland soil plus denitrified N revealed that mineralization of cattle manure-, pressmud-, poultry manure- and green manure-N over 16 days was 12, 20, 29 and 44%, respectively, and was inversely related to C:N ratio (R ²=0.703, P=0.05) and directly to N content of organic manure (R ²=0.964, P=0.01). Manure-C mineralized over 16 days ranged from 6% to 50% in different manures added to soil under different moisture regimes and was, in general, inversely related to initial C:N ratio of manure (R ²=0.690, P=0.05). Cumulative denitrification losses over 16 days in control soils (without manure) under upland, nearly saturated, and flooded conditions were 5, 23, and 24 mg N kg^–1, respectively. Incorporation of manures enhanced denitrification losses by 60-82% in upland, 52–163% in nearly saturated, and 26–107% in flooded soil conditions over a 16-day period, demonstrating that mineralized N and C from added manures could result in 2- to 3-fold higher rate of denitrification. Cumulative denitrification losses were maximal with green manure, followed by poultry manure, pressmud and cattle manure showing an increase in denitrification with increasing N content and decreasing C:N ratio of manure. Manure-amended nearly saturated soils supported 14–35% greater denitrification than flooded soils due to greater mineralization and supply of C.     

江苏省集约化养殖畜禽粪便盐分含量及分布特征分析

该文针对目前畜禽粪便中盐分含量较高、在农用过程中可能对农田土壤次生盐渍化构成威胁等问题,在江苏省采集和分析了150家养殖场（户）的180个畜禽粪便样品中的盐分含量,比较了不同畜禽种类以及不同区域之间粪便盐分含量的差异。研究结果表明,江苏省畜禽粪便中盐分含量（干粪）平均值为9.7 g/kg,检出范围1.8～24.2 g/kg;不同畜禽种类粪便中盐分含量为鸡粪（14.8 g/kg）〉猪粪（8.1 g/kg）〉牛粪（6.0 g/kg）,三者之间差异达到显著水平（p〈0.05）;蛋鸡粪盐分含量（16.7 g/kg）显著高于肉鸡粪（12.0 g/kg）;江苏省盐分含量环境背景值较高的沿海地区、徐淮地区猪粪、鸡粪中盐分含量显著高于盐分含量环境背景值较低的苏锡常地区、沿江地区。因此,在施用盐分含量较高的畜禽粪便以及在盐分含量环境背景值较高的地区施用畜禽粪便时,应关注畜禽粪便施用对农田土壤次生盐渍化的影响。     

Effect of Drying on Phosphorus Distribution in Poultry Manure

Abstract

Laboratory drying may alter manure phosphorus (P) distribution. The effects of freeze, air (22°C), and oven (65°C) drying on sequentially fractioned poultry manure P were examined. Higher drying temperatures resulted in lower percentage of dry matter. Increased H₂O‐ and decreased sodium bicarbonate (NaHCO₃)‐extractable P with drying provided evidence that drying increases poultry manure P solubility. Labile fractions were predominantly inorganic P (P_i), whereas sodium hydroxide (NaOH) and hydrochloric acid (HCl) fractions had significant amounts of organic P (P_o). Drying altered H₂O‐ and NaHCO₃‐extractable P_i but had no consistent effect on P_o in these fractions. This work suggests that variations due to drying should be taken into consideration when evaluating manures for P availability or when comparing data in which different drying methods have been utilized.     

Chemical Characterization of Cow Manure and Poultry Manure after Composting with Privet and Cypress Residues

ABSTRACT

Investigating available nutrients and non-essential elements in manures is important for safe management of animal and plant waste. Therefore, this study was carried out to chemically characterize cow manure (CM) and poultry manure (PM) after co-composting with privet and cypress residues. Results showed that heavy metals concentrations in manures varied as Fe > Zn > Mn > Cu > Ni > Pb > Cd. Addition of privet and cypress residues to both manures altered the extractability of heavy metals after composting. Higher concentrations of heavy metals were observed in manures at 1:0 ratio while lowest was noted in both CM and PM composted with plant residues at 1:2 ratio. Total K, Ca, and Mg significantly increased when CM and PM were co-composted with privet and cypress residues. There was an increase in the P content in co-composted CM with privet residual application whereas a reduction in total P was noticed with the addition of cypress plant residues in both manures. Manures amended with plant waste reduced N content. Both CM and PM retained higher NO₃ content without plant residues.     

规模化养殖畜禽粪主要有害成分测定分析研究

随着我国规模化养殖业的快速发展,畜禽粪中重金属、兽药残留、盐分及有害菌等有害污染物的增加,构成影响农田土壤健康功能的限制因素,甚至带来生态环境风险。对我国7个省、市、自治区的典型规模化养殖畜禽粪的主要化学组成进行了测定。结果表明,规模化养殖畜禽粪中富含有机质、氮、磷、钾及钙、镁、铁、钠、锰、钴等矿质元素;砷、铜、锌、铬等重金属及盐分含量较高,55个猪粪、鸡粪样中,Cu、Zn、Cr、As含量变幅分别为10.7～1591mg/kg、71.3～8710.mg/kg、0～688.mg/kg、0.01～65.4.mg/kg。同时多有四环素类抗生素残留,32个猪粪样中,土霉素、四环素、金霉素平均含量分别为9.09.mg/kg、5.22.mg/kg、3.57.mg/kg;23个鸡粪样中,土霉素、四环素、金霉素平均含量分别为5.97.mg/kg2、.63.mg/kg1、.39.mg/kg。因此,规模化养殖畜禽粪对农田施用后存在潜在危害性,规模化养殖畜禽粪必须进行无害化处理,才能资源化利用。     

皖南宣城市广德县农用地土壤有机质含量演变

有机质含量是决定土壤肥力的一个重要属性。本文对比分析了皖南宣城市广德县1980s的第二次土壤普查和2008年的测土配方施肥项目获取的农用地土壤有机质含量,分析了其变化的机制,提出了提高土壤有机质含量的对策。20多年来广德县农业用地土壤有机质含量总体上升高了1.48g/kg,升幅为6.10%。县南部和中部土壤有机质含量呈提高的趋势,而北部地区呈降低的趋势。灌溉水田、望天田、旱地、园地的土壤有机质含量均有所提高。为提高土壤有机质含量,应继续实施秸秆还田和适度的少耕/免耕,加强畜禽粪便施用和绿肥种植。     

Nitrogen mineralization in soils amended with composted and uncomposted poultry litter

Abstract

When applied to land, poultry litter can be a valuable source of plant macro‐ and micro‐nutrients. However, if poultry litter is overapplied, then its mineralized nitrogen (N) can contaminate ground and surface waters. Composting poultry litter may slow down the rate of N mineralization thereby reducing the risk of environmental pollution. The objective of this work was to determine if N mineralization from composted poultry litter is slower than that from uncomposted poultry litter when these materials are mixed with soil. Two composted broiler litters, one composted hen manure, and two uncomposted broiler litters were mixed with Dothan loamy sand (pH 4.3) and Hiwassee fine sandy loam (pH 5.5), and incubated at 25°C for 56 d. Subsamples for inorganic N determinations were taken at 1, 2, 4, 7, 14, 21, 28, and 56 d. After 56 d, the proportion of organic N mineralized ranged from 0.4 to 5.8% for the composted materials, and from 25.4 to 39.8% for uncomposted broiler litters. These results indicate that composted poultry litter releases N more slowly than uncomposted poultry litter, and therefore poses less environmental risk than uncomposted poultry litter.