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1.
Organic amendments recycle nutrients, but N2O emissions are both environmental and agronomic concerns. We conducted a 4-year field experiment to determine no-till barley (Hordeum vulgare L.) yield and nutrient uptake and soil N2O emissions following a single application of six amendment treatments: (1) no amendment (Check); (2) synthetic N fertilizer (Fert); (3) fresh beef cattle feedlot manure (ManureF); (4) beef cattle feedlot manure compost (CompostR); (5) beef cattle feedlot manure composted with cattle mortalities (CompostM); and (6) separated solids from anaerobically digested cattle feedlot manure (ADM). Barley grown in Year 1 (2006), Year 2 (2007), and Year 4 (2009) (with Year 3 (2008) under fallow) had higher grain yields from ManureF (4.73 Mg ha?1) in Year 2 and ADM (6.30 Mg ha?1) in Year 4 (p < 0.05) than other treatments. The grain N and P contents were not affected (p > 0.05), but N uptake over 3 years (112.8 kg N ha?1 yr?1), and P uptake in Year 1 (19.1 kg ha?1 yr?1) and Year 2 (14.3 kg ha?1 yr?1) from ManureF, were higher (p < 0.05×) than other treatments. The cumulative N2O emissions from ManureF in Year 1 (1.488 kg N ha?1) and from ADM in Year 2 (1.072 kg N ha?1) were higher (p < 0.05) than other treatments while the fraction of applied N emitted as N2O was small (0.00 to 0.79%) and not affected by treatment. However, the percentages of applied N emitted as N2O from compost and ADM were similar to synthetic fertilizer and livestock manure.  相似文献   

2.
In this research, a sequential fractionation procedure coupled with enzyme hydrolysis was used to categorize the phosphorus (P) forms of 18 manure samples collected from in-barn composted bedded pack (beef manure), anaerobic digestion with liquid–solid separation (dairy manure), and liquid–solid separation systems (dairy manure). This research also determined the effects of those P forms on the increase in soil test P (STP) of five soil series. The soils used had initial Bray-1 P ranging from 16 to 43 mg P kg?1. Total dry-ash P (Pt) of the manures ranged from 1.4 to 15.0 g P kg?1; total inorganic P (Pit) accounted for 20 to 81 % of Pt; and enzymatically hydrolysable P (Pet) accounted for 5 to 26 % of Pt. Liquid–solid separation tended to concentrate the manure P in the liquid fractions. In contrast, anaerobic digestion did not affect the manure P distribution compared with the undigested raw manure from the same system. No differences in P distribution were found for the compost bedded pack manure. In the soil incubation study, manure and fertilizer were applied at 40 mg total P kg?1. Separated liquid manure from two systems tended to increase STP more than the separated solid manures from the same systems. Although anaerobic digestion modified some of the physical and chemical properties of the treated manures, it did not clearly impact how digested manure increased STP compared with the raw manures. Overall, the increase in STP after treated manure application was found to be a function of soil clay content and manure Pit?+?Pet applied.  相似文献   

3.
Abstract

Soil pH can be increased by manure or compost application because feed rations usually contain calcium carbonate. This study was conducted from 1992 to 1996 to evaluate effects of phosphorus (P) and nitrogen (N)‐based manure and compost application management strategies on soil pH level. Composted and uncomposted beef cattle (Bos taunts) feedlot manure was applied to supply N or P needs of corn (Zea mays L.) for either a one‐ or two‐year period. Phosphorus‐based manure or compost treatments also received additional fertilizer N (ammonium nitrate) to provide for a total of 151‐kg available N ha‐1 yr‐1. Fertilized and unfertilized checks also were included. Manure and composted manure contained about 9 g CaCO3kg‐1 resulting in application rates of up to 1730 kg CaCO3 ha‐1 in 4 years. The surface soil (0–150 mm) pH was significantly decreased with ammonium nitrate application compared to soil in the unfertilized check or to soil receiving manure or compost. Soil pH was significantly increased with the N‐based management strategy compared with the soil original level. In contrast, 4 yr of P‐based manure and compost application strategy maintained soil pH at the original level. Nitrogen‐based applications resulted in higher soil pH than P‐based. Beef cattle feedlot manure and compost can be good sources of CaCO3 for soils requiring lime addition.  相似文献   

4.
We investigated whether nitrification inhibitor nitrapyrin can reduce nutrient leaching and increase nutrient uptake by corn (Zea mays L.) in cattle manure amended soil. Amendments included non-amended check (CK), urea (Urea), REG (manure from cattle fed barley grain), and DDGS (manure from cattle fed 60% dried distillers grains with solubles), co-applied with or without nitrapyrin and leached or unleached with water. Nitrapyrin reduced (P < 0.01) leaching of nitrate by 56, 32, and 24% from DDGS, REG, and Urea treatments, respectively, and also reduced (P < 0.05) leaching of phosphate (58%), potassium (39%), calcium (39%), and magnesium (39%) from DDGS treatment. While nitrapyrin reduces the rate of ammonium conversion to nitrate, higher magnesium and phosphate levels in DDGS-amended soil favor struvite formation and reduce their leaching. Corn biomass and nutrient uptake were higher (P < 0.01) in DDGS and Urea than CK and REG treatments, but remained unaffected by nitrapyrin. The benefits of nitrapyrin should be further investigated under field conditions.

Abbreviations: DCD, dicyandiamide; DDGS, dried distillers grains with solubles; NI, nitrification inhibitor; TP, total P; TN, total N.  相似文献   


5.
No-tillage and manure application effect on soil organic carbon (SOC) and total nitrogen (N) concentrations were studied under a 27-year-old 4-year rotation consisting corn (Zea mays L.)-soybean (Glycine max L.)-wheat (Triticum aestivum L.)-field pea (Pisum sativum L.). Under each crop, four applied N treatments were control, annual urea-N applications at the rate of 45 and 89 kg N ha?1, and composted beef cattle feedlot manure-N at the rate 179 kg N ha?1 applied once every four year. For each fertilizer treatment, no-till (NT) and conventional till (CT) were compared for basic soil properties, SOC, and total N within 0–15 cm soil. Manure application significantly reduced soil bulk density and increased SOC and total N over urea-N. Particulate organic matter, mineralizable N, and permanganate-oxidizable C fractions significantly related with SOC. Long-term manure additions and no-tillage had potential to improve soil compaction and maintain SOC over chemical fertilizer N and CT.  相似文献   

6.
Nutrient recycling should be effective at balancing nutrient flows in Japanese animal production. This means replacing imported feed with self-produced feed. The Yakumo Experimental Farm of Kitasato University has produced commercial beef under ‘organic’ management, without the use of agricultural chemicals or imported feed, since 2005. Using a data set obtained from 220 ha of grassland and 250 head of cattle over the 5 years from 2008 to 2012, we estimated nitrogen (N) flow. During 2011 and 2012, we measured grass production, cattle production (selling out), soil parameters and atmospheric deposition (from precipitation and atmospheric ammonia concentrations). To determine N fixation by clover (white clover, Trifolium repens L.), we compared grass + clover plots with grass-only plots. Averaged over the period, N components on the 220 ha of grassland comprised 1952 Mg soil N stock, 3.2 Mg N yr?1 in living livestock, 14.3 Mg N yr?1 uptake by grass growth (including 8.6 Mg yr?1 of N fixed by clover), 15.7 Mg N yr?1 applied in composted manure, 1.7 Mg N yr?1 in imported bedding material, 2.8 Mg N yr?1 in deposition and 1.41 Mg N yr?1 in meat production. N in composted manure equaled about 0.8% of the huge soil N stock; N in grass production equaled about 0.7%, of which clover fixation supplied 60%; N deposition was not negligible; and N export by meat production was minor. These results show that on this organically managed farm, soil N stock increased gradually (by 8.6 Mg N yr?1 [220 ha]?1 = 39 kg N ha?1 yr?1 = 0.02% of the soil N stock) and N export was small. Our findings show that it is possible to balance N inputs with N outputs in a beef cattle enterprise without the need for feed or fertilizer imports.  相似文献   

7.
Phosphorus (P) from manure can become an environmental pollutant if applied to soil at rates in excess of plant uptake. This research examined the effects of composted beef cattle manures from two feeding regimens on soil P storage and forms. Composted manures were applied in the spring before planting (preplant) with incorporation, in spring after planting (postplant) without incorporation, or in winter without incorporation. Soils were sampled following 1 and 2 years of treatment at depths to 15.0 cm. All P fractions from both composted manures increased over pre-amended levels. High-P composted manure increased total P (TP) and inorganic P (IP) more than low-P composted manure. Total P and IP were greater in soils receiving low-P composted manure postplant than in those receiving manure preplant. Accumulation of TP and IP in uppermost depths was greater in the second year of composted manure application than in the first year. Appropriately managing composted manure requires integrating P concentration, time of application, and incorporation.  相似文献   

8.
A field experiment was carried out in northern Vietnam to investigate the effects of adding different additives [rice (Oriza sativa L.) straw only, or rice straw with added lime, superphosphate (SSP), urea or a mixture of selected microorganism species] on nitrogen (N) losses and nutrient concentrations in manure composts. The composts and fresh manure were applied to a three-crop per year sequence (maize–rice–rice) on a degraded soil (Plinthic Acrisol/Plinthaquult) to investigate the effects of manure type on crop yield, N uptake and fertilizer value. Total N losses during composting with SSP were 20% of initial total N, while with other additives they were 30–35%. With SSP as a compost additive, 65–85% of the initial ammonium-N (NH4-N) in the manure remained in the compost compared with 25% for microorganisms and 30% for lime. Nitrogen uptake efficiency (NUE) of fresh manure was lower than that of composted manure when applied to maize (Zea mays L.), but higher when applied to rice (Oriza sativa L.). The NUE of compost with SSP was generally higher than that of compost with straw only and lime. The mineral fertilizer equivalent (MFE) of manure types for maize decreased in the order: manure composted with SSP?>?manure composted with straw only and fresh manure?>?manure composted with lime. For rice, the corresponding order was: fresh manure?>?manure composted with SSP/microorganisms/urea?>?manure composted with lime/with straw alone. The MFE was higher when 5 tons manure ha?1 were applied than when 10 tons manure ha?1 were applied throughout the crop sequence. The residual effect of composted manures (determined in a fourth crop, with no manure applied) was generally 50% higher than that of fresh manure after one year of manure and compost application. Thus, addition of SSP during composting improved the field fertilizer value of composted pig manure the most.  相似文献   

9.
Abstract

Castor and sunflower, drought‐tolerant crops, are cultivated in the semi‐arid tropics of the world. The nutrient‐rich residues of these crops are mostly burnt because of their high C/N (C/N)‐ratios. These high C/N‐ratio residues can be composted and recycled successfully, if they are supplemented with other low C/N‐ratio farm‐based organics and some chemical additives. To study the rate kinetics and half‐life of decomposition of castor (C/N ratio: 75∶90) and sunflower (C/N ratio 57∶47) residue mixtures and the manure value of the compost thus prepared, two on‐farm experiments were conducted at Hayathnagar Research Farm (17° 18′ N latitude, 78° 36′ E longitude, and an elevation of 515 m above sea level) of Central Research Institute for Dryland Agriculture, Hyderabad, India. The decay rate constants obtained on the basis of the exponential functions using the data on weight loss, C concentration, and C/N ratios indicated that among the four combinations of treatments, castor stalks+gliricidia loppings+cattle dung had the fastest rate of decomposition with an average rate constant value of 0.0043 day?1. To achieve 50% decomposition (half‐life), the time periods computed for castor stalks+gliricidia loppings+cattle dung and sunflower stalks+gliricidia loppings+cattle were 197 and 278 days, respectively. On an average basis, sunflower‐based manure contained a significantly higher amount of total N (14.6 gm kg?1) than castor‐based manures (12.2 gm kg?1). The corresponding total hydrolyzable N values were 8.2 and 8.15 gm kg?1, respectively. Amino acid N was found to be the predominant constituent of the total acid hydrolyzable N in the manure. Use of earthworms in composting enriched the manure in terms of mineral [nitrate (NO3)+ammonium (NH4)‐N] and hexosamine‐N fractions. The full article deals with the decomposition patterns (periodical changes in weight loss, C concentration and C/N ratios), decay‐prediction functions, composting, and manure quality of the castor‐ and sunflower‐based residue mixtures.  相似文献   

10.
Abstract

The rate and timing of manure application when used as nitrogen (N) fertilizer depend on N‐releasing capacity (mineralization) of manures. A soil incubation study was undertaken to establish relative potential rates of mineralization of three organic manures to estimate the value of manure as N fertilizer. Surface soil samples of 0–15 cm were collected and amended with cattle manure (CM), sheep manure (SM), and poultry manure (PM) at a rate equivalent to 200 mg N kg?1 soil. Soil without any amendment was used as a check (control). Nitrogen‐release potential of organic manures was determined by measuring changes in total mineral N [ammonium‐N+nitrate‐N (NH4 +–N+NO3 ?–N)], NH4 +–N, and accumulation of NO3 ?–N periodically over 120 days. Results indicated that the control soil (without any amendment) released a maximum of 33 mg N kg?1soil at day 90, a fourfold increase (significant) over initial concentration, indicating that soil had substantial potential for mineralization. Soil with CM, SM, and PM released a maximum of 50, 40, and 52 mg N kg?1 soil, respectively. Addition of organic manures (i.e., CM, SM, and PM) increased net N released by 42, 25, and 43% over the control (average). No significant differences were observed among manures. Net mineralization of organic N was observed for all manures, and the net rates varied between 0.01 and 0.74 mg N kg?1 soil day?1. Net N released, as percent of organic N added, was 9, 10, and 8% for CM, SM, and PM. Four phases of mineralization were observed; initial rapid release phase in 10–20 days followed by slow phase in 30–40 days, a maximum mineralization in 55–90 days, and finally a declined phase in 120 days. Accumulation of NO3 ?–N was 13.2, 10.6, and 14.6 mg kg?1 soil relative to 7.4 mg NO3 ?–N kg?1 in the control soil, indicating that manures accumulated NO3 ?–N almost double than the control. The proportion of total mineral N to NO3 ?–N revealed that a total of 44–61% of mineral N is converted into NO3 ?–N, indicating that nitrifiers were unable to completely oxidize the available NH4 +. The net rates of mineralization were highest during the initial 10–20 days, showing that application of manures 1–2 months before sowing generally practiced in the field may cause a substantial loss of mineralized N. The rates of mineralization and nitrification in the present study indicated that release of inorganic N from the organic pool of manures was very low; therefore, manures have a low N fertilizer effect in our conditions.  相似文献   

11.
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.  相似文献   

12.
A pot experiment, in which composted pig manure was applied to soils at rates of 0%, 0.5%, 1.5%, 3.0%, and 5.0% (W/W) to simulate additions of different amounts of cadmium (Cd), copper (Cu), and zinc (Zn) to soil, was conducted to assess accumulation of metals by rice (Oryza sativa L.) plants from soils treated with manure. Results indicated that Cd concentrations in rice grains were more than the limit of 0.2 mg kg?1 when 0.14 mg kg?1 or more Cd was loaded to Ferralsols by manure application, but it was not more than the limit in Calcaric Cambisols. Zinc contents in polished rice grains did not exceed the permissible limit of 50 mg kg?1 in two soils. Copper concentrations in rice grain were slightly more than the limit of 10 mg kg?1 in Ferralsols but not in Calcaric Cambisols. Results suggested greater risk of heavy‐metal contamination from manure to paddy rice in Ferralsols than in Calcaric Cambisols.  相似文献   

13.
 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.  相似文献   

14.
In this study, 24 years (1990–2013) of data from a long-term experiment, in Stillwater, Oklahoma (OK), were used to determine the effect of beef manure on soil test phosphorus (STP), soil organic carbon (SOC), and winter wheat (Triticum aestivum L.) yield. Beef manure was applied every 4 years at a rate of 269 kg nitrogen (N) ha?1, while inorganic fertilizers were applied annually at 67 kg N ha?1, 14.6 kg phosphorus (P) ha?1, and 27.8 kg potassium (K) ha?1 for N, P, and K, respectively. Averaged across years, application of beef manure, and inorganic P maintained STP above 38 mg kg?1 of Mehlich-3 extractable P, a level that is far beyond crop requirements. A more rapid decline in SOC was observed in the check plot compared to the manure-treated plot. This study shows that the application of animal manure is a viable option to maintaining SOC levels, while also optimizing grain yield.  相似文献   

15.
Soil cultivation changes and usage of agricultural wastes can have profound impacts on greenhouse gas (GHG) emission from soil. In this study, the effects of soil cultivation and organic amendment on GHG emission were investigated using aerobic incubation. Surface soil (0–20 cm) from (1) rice–legume consecutive rotation (Rice) and (2) recently (<3 years) converted from rice field to plastic-covered intensive vegetable and flower production (VegC) were collected in Kunming, P.R. China. Rose (Rosa rugosa Thunb.) residues and cattle manure were applied at 5% by weight. Results indicated that N2O and CO2 fluxes were significantly influenced by soil cultivation, organic amendment, incubation time and their interaction (p <0.05). Applying cattle manure increased, while rose residue decreased, cumulative N2O emissions from soil (84 days). Rose residue application significantly increased cumulative CO2 emissions with peak values of 6371 (Rice) and 7481 mg kg?1 (VegC), followed by cattle manure addition figure of 2265 (VegC) and 3581 mg kg?1 (Rice). Both were significantly higher (p <0.05) than the un-amended Control at 709 (VegC) and 904 mg kg?1 (Rice). Our study demonstrates that a low C/N ratio in cattle manure is better than a high C/N ratio in rose residue in regard to reducing the global warming potential of agricultural soil.  相似文献   

16.
To promote the use of animal waste in agriculture and prevent environmental pollution, an alternative product from the waste should be appraised. This necessitated the study to characterize animal manure ashes and determine its effect on soil pH and electrical conductivity (EC) dynamics. Dried manures of cattle, goat, and poultry, their ashes, and nitrogen (N)–phosphorus?–potassium were applied to soil at 120 kg N ha?1.? Soils collected fortnightly were analyzed for pH and EC. Results indicated that nutrients in manure ashes were comparable to that of dried manures. Changes in pH and EC were not predictable, application of manure ash increased pH by 12% and 13%, 23% and 14%, 20% and 3% while EC increased by 616% and 109%, 1274% and 156%, 2992% and 458%, relative to dried manures and control during incubation, screenhouse, and field experiments, respectively. It was concluded that incorporation of manure ashes increased soil pH and EC although dynamics were unpredictable.  相似文献   

17.
A sandy soil was amended with different types of sewage sludge (digested, dried, and composted) and pig slurry. The composted sludges displayed higher organic‐matter stability (39–45%) than only digested sludge (26–39%) or digested + dried sludge (23–32%). The microbial biomass of the dried sludge was undetectable. Digested and composted sludges and pig slurry displayed microbial biomasses (12492–13887 µg g?1, 1221–2050 µg g?1, and 5511 µg g?1, respectively) greater than the soil (108 µg g?1). The wastes were applied at seven doses, ranging from 10 to 900 g kg?1. Soils were incubated for 28 days. Substrate‐induced respiration (SIR) was measured for 12 consecutive hours on day 1 and on day 28. The results showed that SIR increased with the dose of organic amendment. However, SIR decreased when moderate doses of pig slurry or high doses of digested + dried sludge were tested. The possibility of using this inhibition as an ecotoxicological indicator is discussed.  相似文献   

18.
通过大田试验研究了不施有机肥(CK)、施用平菇栽培废料(T1)、施用干腐熟牛粪(T2)和烘干鸡粪(T3)在种植黄瓜01～50.d内土壤中活性有机质和4种土壤酶活性的变化。结果表明:施入不同有机肥对土壤总有机质含量的影响为烘干鸡粪平菇栽培废料干腐熟牛粪对照;对活性有机质含量的影响为平菇栽培废料烘干鸡粪干腐熟牛粪对照;施用平菇栽培废料的土壤中脲酶、转化酶和脱氢酶活性最高,施用干腐熟牛粪的土壤中过氧化氢酶活性最高。相关性分析显示,脲酶、转化酶和脱氢酶活性与土壤活性有机质显著相关。用平菇栽培废料做有机肥能有效提高土壤活性有机质含量和土壤酶活性。  相似文献   

19.
Abstract

Most measurements of dairy manure nitrogen (N) availability depend on net changes in soil inorganic N concentration over time, which overlooks the cycling of manure N in the soil. Gross transformations of manure N, including mineralization (m), immobilization (i), and nitrification (n), can be quantified using 15N pool dilution methods. This research measures gross m, n, and i resulting from application of four freeze‐dried dairy manures that had distinctly different patterns of N availability. A sandy loam soil (coarse‐loamy, mixed, frigid Typic Haplorthod) was amended with four different freeze‐dried dairy manures and incubated at 25°C with optimal soil water content. The dilution of 15ammonium (NH4+) during a 48‐h interval (7–9 d and 56–58 d after manure application) was used to estimate m, whereas the dilution of 15nitrate (NO3 ?) was used to estimate n. Gross immobilization was calculated as gross minus net mineralization. Gross mineralization in the unamended soil was similar at 7‐ to 9‐d and 56‐ to 58‐d intervals and was significantly increased by the application of manures. For both amended and unamended soil, m was much greater (i.e., three‐ to nine‐fold) than estimated net mineralization, illustrating the degree to which manure N can be cycled in soil. At the early interval, both m and i were directly related to the manure C input, demonstrating the linkage between substrate C availability and N utilization by soil microbes. This research clearly shows that the application of dairy manures stimulates gross N transformation rates in the soil, improving our understanding of the impact of manure application on soil N cycling.  相似文献   

20.
The decomposition and the associated nitrogen (N) dynamics of organic N sources are affected by their contact with soil. While several authors have examined the effect of surface application or incorporation of crop residues on their decomposition rate, less information is available about the relationship between the placement of animal manure and their N mineralization rate. This study investigated the influence of chicken manure and cattle manure placement on soil N mineralization. The manures were incorporated or surface applied at 175 mg N kg?1, and N release was periodically determined over 56 days by measuring inorganic N [nitrate (NO3 ?) N and ammonium (NH4 +) N] in a 2 M potassium chloride (KCl) extract at a ratio of 1:10 (w/v). Results indicated that the control soil released a maximum of 64 mg N kg?1 soil at day 21, a sixfold increase over the initial concentration, which indicates its substantial mineralization potential. Manure treatments showed an initial increase in net NO3 ?-N content at the start of the experiments (until day 7) before an extended period of immobilization, which ended at day 21 of the incubation. A small but positive net N mineralization of all manures was observed from 28 days of incubation. At each sampling time, the mean mineral N released from the control was significantly less (P < 0.01) than surface-applied chicken manure, incorporated chicken manure, and surface-applied cattle manure. Treatments exceptions were at days 21 and 28 where N immobilization was at its peak. In contrast, incorporation of cattle manure showed a different N-release pattern, whereby the mineral N amount was only significantly greater than the control soil at days 42 and 56 with 84 and 108 mg N kg?1 soil respectively. Incorporation of chicken manure and cattle manure did not favor nitrification as much as surface application and cattle manure caused a much greater immobilization when incorporated than when surface applied.  相似文献   

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