Nitrate leaching from an organic dairy crop rotation: the effects of manure type, nitrogen input and improved crop rotation

Abstract. Four management systems combining high and low livestock densities (0.7 and 1.4 livestock units ha⁻¹) and different types of organic manure (slurry and straw based FYM) were applied to an organic dairy crop rotation (undersown barley – grass–clover – grass–clover – barley/pea – oats – fodder beet) between 1998 and 2001. The effects of the management systems on crop yields and nitrate leaching were measured. In all four years, nitrate leaching, as determined using ceramic suction cups, was higher in the three crops following ploughing of grass–clover than under the barley or grass–clover. Overall, no significant differences in nitrate leaching were observed between the management systems. However, the replacement of the winter wheat crop used in the earlier experimental period (1994–97) by spring oats with catch crops in both the preceding and succeeding winters reduced nitrate leaching compared with the earlier rotation. Increasing the livestock density, which increased manure application by c. 60 kg total N ha⁻¹, increased crop yields by 7 and 9% on average for FYM and slurry, respectively. Yields were 3–5% lower where FYM was used instead of slurry. The experiment confirmed the overriding importance of grassland N management, particularly the cultivation of the ley, in organic dairy crop rotations.     

Nitrate leaching in an organic dairy/crop rotationas affected by organic manure type, livestock densityand crop

Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO₃-N l^?1 in 1^st year grass-clover to 20–50 mg NO₃-N l^?1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2^nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha^?1 year^?1 (from 0.9 to 1.4 livestock units ha^?1) only increased leaching by 6 kg NO₃-N ha^?1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO₃-N ha^?1). Leaching losses were lowest in 1^st year grass-clover (20 kg NO₃-N ha^?1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l^?1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.     

施用钾肥和有机肥对小麦产量、品质的影响

利用布置在河北玉田县的一个钾肥定位试验,研究了在施用氮磷化肥的基础上,施用钾肥和有机肥对小麦子粒产量、17种氨基酸、粗蛋白和粗淀粉含量的影响。结果表明,施用钾肥明显提高了小麦子粒产量,同时提高了天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量;施用有机肥明显提高了蛋氨酸、赖氨酸和脯氨酸的含量;钾肥和有机肥配合施用明显提高了产量、天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量,对上述氨基酸的提高幅度均在10%以上。施用钾肥和(或)有机肥提高了小麦子粒的氨基酸总量、粗蛋白含量,但降低了粗淀粉含量。     

Nitrate leaching following autumn and winter application of animal manures to grassland

Abstract. Under a UK Government consultation procedure announced in 2001, it was proposed that measures agreed within already designated Nitrate Vulnerable Zones (NVZ 's) would be extended to include a considerably increased area of England, Wales and Scotland. Since existing NVZ 's in the UK have included relatively little grassland, it is important to examine how nitrate losses from grassland areas, especially from animal manures, one of the major potential sources of nitrate loss, can be minimized. Experiments were carried out on freely draining grassland soils at four sites (Devon, Hampshire, Shropshire and N Yorkshire) representative of a wide range of climatic and farming conditions across lowland England, over a four year period, 1990/91 to 1993/94. Slurry was applied to experimental plots over a range of times (including June and then monthly, from September to January) at a target rate of 200 kg N ha^–1. Nitrogen leaching over the four years ranged from 0 to >50% of applied slurry N, with the largest losses occurring following applications in the September to November period. The use of a nitrification inhibitor with slurry applied in November failed to provide consistent reduction in nitrate leaching.
A strategy to reduce the risk of N leaching from manures applied to freely draining grassland soils must take account of the characteristics of the manure, in particular its N content, the application rate and the amount of excess rainfall following application. The experimental results suggest that slurry applications to freely draining grassland, in September, October and November should generally be avoided, the rationale for this being dependent on the amount of excess rainfall subsequent to application. Farmyard manure represents a lower risk and does not justify the restrictions on application timing that appear to be necessary with slurry.     

Phytoextractability of lead from soil by some oilseed crops as affected by sewage sludge and farmyard manure

Abstract

Screenhouse experiments were conducted to study the phytoextractability of lead (Pb) by three oilseed crops (Brassica juncea, Brassica napus and Eruca sativa) from Pb enriched (i.e. 0, 200, 400, 600 and 800 mg Pb kg^?1 soil) unamended, sewage sludge-amended (SS-amended) and farmyard manure-amended (FYM-amended) sandy loam soil. Chlorotic symptoms and stunted growth were observed at Pb₆₀₀ and Pb₈₀₀ treatments. Sewage sludge and FYM slightly decreased chlorosis. The biomass production for amendment treatments followed the order: FYM-amended > SS-amended > Unamended soil, and for species: Brassica juncea > Brassica napus > Eruca sativa. The Pb concentration followed the order: leaf > stem > seed, Brassica napus > Brassica juncea > Eruca sativa, and SS-amended > Unamended > FYM-amended soils. The Pb uptake followed the order: Brassica juncea > Brassica napus > Eruca sativa, and SS-amended > Unamended > FYM-amended soils. Exchangeable and Fe-Mn oxide bound fractions decreased and organic matter bound fraction increased with sewage sludge and FYM. The carbonate bound fraction considerably decreased with FYM.     

Performance of wheat (Triticum aestivum) to incorporation of organic manure and bioinoculants

A field experiment was conducted to evaluate the effect of integrated use of farmyard manure and bio-inoculants on wheat productivity for two years in succession. Increasing levels of farmyard manure (FYM) up to 15 t ha^?1 significantly (p ≤ 0.05) improved the dry matter accumulation, effective tillers per m row length, and grain weight per spike in both the years. Application of 15 t ha^?1 FYM caused significant increase in spikelets per spike and grains per spike over control and 5 t ha^?1 during two consecutive years. Inoculation with MSX-9 strain of Azotobacter chroococcum produced significantly higher dry matter accumulation to 25.63, 13.33, 7.78 and 23.66, 8.35, 5.50% over uninoculation, Azospirillum brasilense (SP-7) and Azospirillum lipoferum (A-5) at harvest during 1999–2000 and 2000–2001, respectively. Incorporation of 15 t ha^?1 FYM significantly (p ≤ 0.05) enhanced grain and straw yield to 62.45 and 38.05%; 56.66 and 36.28%; 59.42 and 37.52% over control in 1999–2000, 2000–2001 and pooled analysis, respectively. The grain and straw yield of wheat significantly (p ≤ 0.05) enhanced to 26.51, 10.10, 7.54 and 14.45, 5.77, 3.16% through A. chroococcum (MSX-9), A. brasilense (SP-7) and A. lipoferum (A-5) over uninoculation.     

Fertilizer value of nitrogen in hen and broiler manure after application to spring barley using different application timing

The nitrogen (N) fertilizer effect of layer hen and broiler manure applied at different times on spring barley yield was studied in seven Swedish field experiments during 2005–2008. Two experiments had parallel field incubations to study N release after fertilizer application. The effect of total N in manure on N offtake was 30–40% that of mineral N, except in a dry year, when the effect was very low. Although the relative proportions of ammonium N, uric acid N and other N differed between the hen and broiler manure, the effect of total N was similar for both. In field incubations, mineral N decreased from 75 to 60% of total N applied in hen manure, whereas it increased from 20 to 50% in broiler manure, because of net immobilization and release, respectively. The limited fertilizer nitrogen replacement value, corresponding to only 30–40% of total N, could be as a result of ammonia volatilization after rather shallow incorporation with harrow. Net N release from broiler manure lasted for 6–8 weeks after application, after which it generally ceased. In some cases, manure application in early spring gave better yield effects than application at sowing, probably because of better synchronization of the N release with crop N requirements. The residual N effect on the N offtake in crop in the year after manure application was on average 3% of the total N applied, equivalent to a fertilizer replacement value of about 6%.     

Effects of animal manure application and crop plants upon size and activity of soil microbial biomass under organically grown spring barley

Temporal behaviour of microbial biomass C, N and respiration was measured under barley crops in two experiments on successive years in a recently converted organic production system in Scotland. Soils were fertilised with farmyard manure or poultry manure. Control soils received no manure at the start of the growing season. The effects of plants was also investigated by maintaining fallow subplots. C-flush values approximately doubled over the growing season in both years of the trial, showing a decline to pre-sowing values between the two seasons. This occurred in all soils, whether manured or not, or planted or fallow. Manure tended to increase the C-flush in the 2nd year only. N-flush in the 2nd year showed no increase in planted control plots but did increase in fallow soils. Manures significantly increased the N-flush. Respiration rates were stimulated by the presence of plants. Respiration rates were measured from soils taken from the field at post-sowing, mid-season and post-harvest occasions and incubated under constant conditions for up to 1 year. Here there was evidence that the effects of sampling and adjusting the moisture status could be as great upon microbial activity as the addition of the manures. C-flush also showed a consistent and persistent increase in these incubated soils. This suggests that the fundamental C-supplying characteristics of these soils was such that the biomass was moving towards a new equilibrium value fuelled by the relatively recent introduction of the organic farming regime. Received: 27 February 1996     

CO2 emission in an intensively cultivated loam as affected by long-term application of organic manure and nitrogen fertilizer

A long-term field experiment was conducted to examine the influence of mineral fertilizer and organic manure on the equilibrium dynamics of soil organic C in an intensively cultivated fluvo-aquic soil in the Fengqiu State Key Agro-Ecological Experimental Station (Fengqiu county, Henan province, China) since September 1989. Soil CO₂ flux was measured during the maize and wheat growing seasons in 2002-2003 and 2004 to evaluate the response of soil respiration to additions and/or alterations in mineral fertilizer, organic manure and various environmental factors. The study included seven treatments: organic manure (OM), half-organic manure plus half-fertilizer N (NOM), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK). Organic C in soil and the soil heavy fraction (organo-mineral complex) was increased from 4.47 to 8.61 mg C g⁻¹ and from 3.32 to 5.68 mg C g⁻¹, respectively, after the 13 yr application of organic manure. In contrast, organic C and the soil heavy fraction increased in NPK soil to only 5.41 and 4.38 mg C g⁻¹, respectively. In the CK treatment, these parameters actually decreased from the initial C concentrations (4.47 and 3.32 mg C g⁻¹) to 3.77 and 3.11 mg C g⁻¹, respectively. Therefore, organic manure efficiently elevated soil organic C. However, only 66% of the increased soil organic C was combined with clay minerals in the OM treatment. Cumulative soil CO₂ emissions from inter-row soil in the OM and NPK treatments were 228 and 188 g C m⁻² during the 2002 maize growing season, 132 and 123 g C m⁻² during the 2002/2003 wheat growing season, and 401 and 346 g C m⁻² yr⁻¹ in 2002-2003, respectively. However, during the 2004 maize growing season, cumulative soil CO₂ emissions were as high as 617 and 556 g C m⁻², respectively, due to the contribution of rhizosphere respiration. The addition of organic manure contributed to a 16% increase in soil CO₂ emission in 2002-2003 (compared to NPK), where only 27%, 36% and 24% of applied organic C was released as CO₂ during the 2002 and 2004 maize growing seasons and in 2002-2003, respectively. During the 2002/2003 wheat growing season, soil CO₂ flux was significantly affected by soil temperature below 20 °C, but by soil moisture (WFPS) during the 2004 maize growing season at soil temperatures above 18 °C. Optimum soil WFPS for soil CO₂ flux was approximately 70%. When WFPS was below 50%, it no longer had a significant impact on soil CO₂ flux during the 2002 maize growing season. This study indicates the application of organic manure composted with wheat straw may be a preferred strategy for increasing soil organic C and sequestering C in soil.     

有机肥对小麦根系生长及根系衰老进程的影响

采用土柱栽培与室内分析相结合的方法,研究了有机肥对小麦根系生长及根系衰老进程的影响。结果表明,有机肥可促进小麦根系的生长和根系在深层土壤中的分布,使小麦根系的总鲜重和深层土壤根系鲜重明显增加;提高不同土层、特别是深层土壤中根系的活力,使小麦生长后期保持较高的根系吸收养分的能力。有机肥可促进根系对氮、磷、钾的吸收和向子粒中的转移,使氮、磷、钾在子粒中的分配量增加;而且能抑制根系的膜脂过氧化作用,使不同土层小麦根系SOD活性提高、MDA含量降低,从而延缓了根系的衰老。     

Potassium retention and leaching in an organic crop rotation on loamy sand as affected by contrasting potassium budgets

Abstract. In organic farming, potassium (K) deficiency may become a significant problem due to nutrient import restrictions. Knowledge about potential K leaching in systems with different K budgets is therefore important for effective agricultural management. We investigated the effect of four organic farming systems (two livestock densities in combination with two types of organic manure) on crop yields, K leaching and K balances in a six course crop rotation from 1993/94 to 1997/98. Average K concentrations in soil water extracted by means of ceramic suction cups at 1 m depth were 0.6 mg K l⁻¹ corresponding to a K leaching loss of 1.5 kg ha⁻¹ yr⁻¹ which was less than expected from values reported in the literature. Variation in K budgets from −12 to +30 kg ha⁻¹ yr⁻¹ did not affect K leaching. In an additional experiment with application of 988 kg K ha⁻¹ as KCl, K leaching accounted for only 0.2% of the applied K although 40% of the accompanying Cl was leached. The main part of the applied K was retained in the topsoil. It was concluded that K leaching was a result of the fertilizer history rather than of the current K budget.     

在含盐新成土上施加有机肥和化学改良剂对土壤性质和作物产量的影响

A field experiment was conducted for two consecutive years in a farmer‘s field at Haji Mora Village, Dera Ismail Khan (D.I. Khan) in the Northwest Frontier Province (NWFP) of Pakistan to compare various management practices, such as the effect of various organic manures and gypsum in a rice-wheat cropping system on a saline-sodic Entisol (Zindani soil series). The treatments consisted of 1) a control (rice-wheat), 2) gypsum, 3) farmyard manure (FYM), 4) berseem (Trifolium alexandrinum L.) as green manure (GM), and 5) dhancha (Sesbania sp.) as GM. All treatments increased yields of both rice and wheat significantly (P (0.01) over the control, with the green manure treatments proving more economical than the others; while they decreased pH, electrical conductivity (EC), and sodium adsorption ratio (SAR) of the soil. Saturation percentage and available water of the soil were raised for all treatments due to an increase in organic matter content of the soil.     

Changes in Vertisol properties as affected by organic amendments application rates

There is considerable global interest in using recycled organic materials because of perceived benefits to soil health and environment. However, information on the effects of organic waste products and their optimal application rates on the quality of heavy clay soils such as Vertisols is sparse. An incubation experiment was therefore conducted using five organic amendments at various rates to identify their optimal application rates, which could improve the quality of the Vertisol. Cotton gin trash, cattle manure, biosolids (dry weight basis 7.5–120 t/ha), chicken manure (dry weight basis 2.25–36 t/ha) and a liquefied vermicast (60–960 L/ha, volumetric basis) changed the soil chemical, physical and microbiological properties compared with a control where no amendments were applied, viz. higher light fraction of organic matter, nutrient content (N and P) and soil microbial activity. Higher application of chicken manure resulted in an increase in dry‐sieved mean weight diameter. Increasing rates of cattle manure increased exchangeable Na concentration and ESP. Although vermicast itself did not contribute a significant amount of N into the soil, when applied at higher rates (60–960 L/ha), its application resulted in increased concentration of NO₃‐N in soil by amounts ranging from 43 to 429%. Optimal application rates for cattle manure and cotton gin trash were 30 t/ha, whereas for biosolids and chicken manure, the optimum rate was 60–18 t/ha, respectively.     

施用禽畜粪对两种土壤As、Cu和Zn有效性的影响

在水稻土和赤红壤中分别以2%和4%(w/w)比例施入含As、Cu和Zn的鸡粪和猪粪,以不施肥为对照进行苋菜盆栽试验,研究施入粪肥对土壤As、Cu和Zn有效性的影响。结果表明,与对照相比,施用粪肥均提高苋菜生物量,但几乎均显著降低苋菜As、Cu和Zn含量。试验前,赤红壤As、Cu和Zn总含量及有效含量明显低于水稻土,但赤红壤中施用粪肥处理的苋菜As、Cu和Zn含量及As和Zn吸收量均极显著高于水稻土的。苋菜收获后,各处理的土壤As总含量和有效含量均较试验前下降,施用高量鸡粪和猪粪处理的土壤总Cu、总Zn及有效Cu、有效Zn均出现累积。与对照比较,施用粪肥提高了土壤As、Cu和Zn的总含量、有效含量及有效含量占各自总量的百分数。如以土壤重金属有效含量增量及有效百分数增加来衡量粪肥提高土壤重金属有效性作用大小,则鸡粪提高土壤As有效性的作用较猪粪大,但其提高Cu、Zn有效性的作用不如猪粪,且高量粪肥处理较低量处理作用明显,粪肥在赤红壤中提高As、Cu和Zn有效性的作用大于在水稻土中。     

Integrated use of organic and inorganic inputs in wheat-fodder maize cropping sequence to improve crop yields and soil properties

A 2-year field study was conducted to evaluate the effect of two organics, farmyard manure and vermicompost, each at three rates (0, 5, 10 t ha^?1 and 0, 1, 2 t ha^?1, respectively), along with two levels of mineral fertilizer (75% and 100% of recommended dose), on crops yields and soil properties under a wheat–fodder maize cropping sequence. Individual addition of organics at a higher level increased yields of wheat and subsequent maize. Soil microbial biomass carbon was enhanced as both a direct and residual effect with the addition of farmyard manure followed by vermicompost and fertilizer treatments, and also by combined addition of manure with either vermicompost or mineral fertilizer. Farmyard manure increased the availability of soil macro- and micronutrients, whereas vermicompost influenced only the availability of micronutrients at wheat harvest. A residual effect of farmyard manure and mineral fertilizers was found for available N. Meanwhile, the residual status of micronutrients in the soil was either maintained or significantly improved due to organic amendments (Mn and Zn with farmyard manure; Fe and Zn with vermicompost). Interaction of farmyard manure and vermicompost at a higher level benefited the next crop by increasing the yield of fodder maize and improving the availability of P and metals in soil.     

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

Abstract. A survey of cattle manure management was undertaken in England and Wales, in 1997, by postal questionnaire sent out to a stratified sample (by unit size) of 1750 dairy and 1750 beef producers. The level of response obtained, with 471 dairy farmers (27%) and 515 beef farmers (29%) returning questionnaires, reflects well on the interest shown by the industry and on the survey design. The survey provided information on manure production and storage, when and how applied and nutrient value. Dairy farms are estimated to produce manures in the form of c. 65% slurry and 35% farmyard manures (FYM) and, beef units, 80%FYM and 20%slurry (based on survey response data, animal numbers and calculations of undiluted outputs of excreta). Slurry storage within both dairy and beef systems is typically up to 3–6 months capacity, although there is no storage for an estimated 16% of dairy and 25% of beef slurry. Autumn and winter spreading is common practice, with 40–50% of slurry and 50–60% of FYM applied at that time. Although some evidence suggests that farmers make little allowance for the nutrient content of manures in planning fertilizer inputs, the results of this survey suggest that many farmers do make some effort to utilize manure nutrients. However, they currently fail to be assured by the advice available to them or they lack confidence in manures as nutrient sources for a number of technical reasons. Information provided by the survey may be important to policy makers, researchers and consultants, as well as farmers.     

Long-term effect of straw and farmyard manure on soil organic matter in field experiment in the Czech Republic

The effect of long-term (45 years) mineral and organic fertilization on soil organic matter (SOM) quantity (organic C and N content) and quality (hot-water-soluble C content, microbial biomass C content, hydrophobic organic components of SOM, soil enzyme activities) was determined in a field experiment established in Trutnov (North Bohemia, sandy loam, Eutric Cambisol). Six treatments were chosen for investigation: unfertilized control, mineral fertilization (NPK), straw N, farmyard manure (FYM) and straw and FYM completed with mineral NPK. Soil samples were taken from the arable layer (0–20 cm) in spring over the period of 2004–2010. The positive effect of FYM on the total organic C and N content, hot-water-soluble C content and hydrophobic organic components of SOM was more than 50% higher than that of straw and mineral N fertilization. Application of straw N increased microbial biomass C content in soil and generated invertase activity above the level of FYM. Hot-water-soluble C content, hydrophobic organic components of SOM and urease activity were positively correlated with total organic C and N content (R = 0.58–0.98; p < 0.05). Addition of mineral NPK to both the straw and FYM emphasized the effect of organic fertilization in most of monitored characteristics.     

Long‐term effects of organic manure and manufactured fertilizer additions on soil quality and sustainable productivity of finger millet under a finger millet–groundnut cropping system in southern India

In a 20‐yr‐old long‐term experiment, the impact of continuous application of organic manures and inorganic fertilizers on soil quality and the sustainability of finger millet production was conducted on two cropping systems: finger millet and finger millet–groundnut on an Alfisol of semi‐arid southern India. The study was conducted from 1992 to 2011 at the All India Coordinated Research Project for Dryland Agriculture, UAS, Bangalore, using a randomized block design. The treatments comprised of T₁: control [no fertilizer and no farmyard manure (FYM) applied], T₂: FYM 10 t/ha, T₃: FYM 10 t/ha + 50% of recommended NPK (50:50:25 kg/ha), T₄: FYM 10 t/ha + 100% of recommended NPK and T₅: 100% recommended NPK. Comparison of long‐term yield data between treatments was used to calculate a ‘sustainability yield index’ (SYI), which was greatest for T₄ (FYM 10 t/ha + 100% of recommended NPK), in both rotational (0.68) and monocropping (0.63) situations. Soil quality indices were determined using principal component analysis linear scoring functions. The key indicators which contributed to the soil quality index (SQI) under rotation were organic C; potentially available N; extractable P, K and S; exchangeable Ca and Mg; dehydrogenase activity and microbial biomass C and N. The largest SQI (7.29) was observed in T₄ (FYM 10 t/ha + 100% NPK), and the smallest (3.70) SQI was for the control. Application of 10 t/ha FYM together with NPK (50:50:25 kg/ha) sustained a mean yield of 3884 kg/ha.     

A survey of the production and use of animal manures in England and Wales. I. Pig manure

Abstract. A survey was undertaken in 1996, by postal questionnaire sent to a stratified sample of 1500 pig producers in England and Wales; 576 (37%) responded. The survey provided data on manure production, manure storage and application strategies (timing, techniques and nutrient recycling to crops).
Total pig manure production, in England and Wales is estimated to be at about 10.03 m t per year, with about 45% as slurry and 55% as FYM, according to this survey, where calculations have been based on undiluted outputs of excreta. About 45% of slurry is stored in above-ground tanks or earth-banked lagoons. Above-ground tanks most commonly held an amount of slurry equivalent to 3–6 months production, but earth-banked lagoons were more variable in capacity and over 20% could hold more than 9 months production of slurry.
Annual statistics on fertilizer use indicate that farmers make little allowance for the nutrient content of manures. However, the results of this survey suggest that farmers generally make a genuine effort to allow for the nutrients applied, but that they currently fail to be assured by the advice available to them or their confidence is lacking for other technical reasons. Autumn represents the peak period for spreading, with 30% of slurry and 50% of FYM applied at that time.     

Effect of organic manures,crop residues and green manure (Sesbania aculeata) on nitrogen and phosphorus transformations in a sandy loam at field capacity and under waterlogged conditions

Summary The influence of the water regime on mineralization and immobilization of N and P was investigated in a calcareous sandy loam incubated with cattle, poultry and green manure (Sesbania aculeata), and wheat and rice straw in a pot experiment. At field capacity, N released from poultry and green manure during the first 4 weeks of incubation was 45% and 59%, respectively. During the next 12 weeks, only around 40% more organic N was mineralized from both sources. In contrast, addition of cattle manure resulted in a period of net N immobilization lasting up to 4 weeks. By the end of 16 weeks of incubation only about 19010 of the added N was mineralized. High rates of N immobilization were observed during the first 4 weeks of incubation of rice or wheat straw with C/N ratios of 78 and 85, respectively. The N mineralization kinetics of poultry and green manure and of untreated soil showed an initial fast reaction followed by a slow release of inorganic N and could be described by two simultaneous first-order reactions. Under waterlogged conditions mineralized N was lost simultaneously in significant amounts possibly through nitrification — denitrification reactions. At field capacity, the largest amount of Olsen P was accumulated in the soil amended with poultry manure, followed by cattle manure. Results from other treatments did not differ much from those of the untreated soil. About 15% of P from poultry manure was mineralized during the 1st week of incubation. In contrast to the field-capacity moisture regime, marked increases in Olsen P in the soils amended with green manure and crop residues were observed under water-logged conditions.