Nitrogen leaching and crop availability in manured catch crop systems in Sweden

Results are presented from five years (1990–1995) of a field leaching experiment on a sandy soil in south-west Sweden. The aim was to study N leaching, change in soil organic N and N mineralization in cropping systems with continuous use of liquid manure (two application rates) and catch crops. N leaching from drains, N uptake in crops and mineral N in the soil were measured. Simulation models were used to calculate the N budget and N mineralization in the soil and to make predictions of improved fertilization strategies in relation to manure applications and changing the time for incorporation of catch crops. In treatments without catch crops, a normal and a double application of manure increased average N leaching by 15 and 34%, respectively, compared to treatment with commercial fertilizer. Catch crops reduced N leaching by, on average, 60% in treatments with a normal application of manure and commercial fertilizer, but only by 35% in the treatment with double the normal application rate of manure. Incorporation of catch crops in spring increased simulated net N mineralization during the crop vegetation period, and also during early autumn. In conclusion, manured systems resulted in larger N leaching than those receiving commercial fertilizer, mainly due to larger applications of mineral N in spring. More careful adaptation of commercial N fertilization with respect to the amounts of NH₄-N applied with manure could, according to the simulations, reduce N leaching. Under-sown ryegrass catch crops effectively reduced N leaching in manured systems. Incorporating catch crop residues in late autumn instead of spring might be preferable with respect to N availability in the soil for the next crop, and would not increase N leaching.     

Effect of biogas technology on nutrient flows for small- and medium-scale pig farms in Vietnam

Increased demand for meat products has led to increased livestock production in Vietnam, which now risks environmental pollution from inappropriate animal manure management on livestock farms. Biogas technology is generally considered an efficient solution for such farms to produce renewable biofuel for use in the household and to reduce the pollution impact from animal waste. However, with biogas technology, farmers may reduce their use of manure for fertilising crops. This field survey investigated nutrient flows on small- and medium-scale livestock farms with and without biogas in Northern Vietnam, in order to identify existing problems and possibilities for sustainable livestock production. A field survey was conducted on 12 pig farms with biogas and 12 pig farms without biogas in Quoc Oai district, Hanoi city. In general, the non-biogas pig farms used on average 3.8 ton compost and 3.1 ton fresh solid manure ha^?1?crop^?1 for each of three crops typically grown per year on their arable land. They discharged on average 16?% of the total manure produced into the environment in liquid form through the public sewage system. On biogas pig farms, the use of fresh solid manure for crops and discharge of liquid manure was lower, as manure was used to produce biogas. However, excessive use of washing water on several of these farms resulted in very dilute slurry (solid manure:water ratio 1:11) entering the biogas digester. This lowered the retention time in the digester (below the optimum range of 35?C55?days), leading to low biogas production rates and possible accumulation of sediment. The digestate was also highly diluted and hence difficult and costly to transport and apply to crops, so it was largely (60?%) discharged to the environment. The input volume of washing water should therefore be reduced to a ratio of 1:5. For better sustainability, appropriate technologies are needed to absorb nutrients from the digestate before discharge and to recycle these nutrients to crops.     

Evaluating the potential of dietary crude protein manipulation in reducing ammonia emissions from cattle and pig manure: A meta-analysis

Dietary manipulation of animal diets by reducing crude protein (CP) intake is a strategic NH₃ abatement option as it reduces the overall nitrogen input at the very beginning of the manure management chain. This study presents a comprehensive meta-analysis of scientific literature on NH₃ reductions following a reduction of CP in cattle and pig diets. Results indicate higher mean NH₃ reductions of 17 ± 6% per %-point CP reduction for cattle as compared to 11 ± 6% for pigs. Variability in NH₃ emission reduction estimates reported for different manure management stages and pig categories did not indicate a significant influence. Statistically significant relationships exist between CP reduction, NH₃ emissions and total ammoniacal nitrogen content in manure for both pigs and cattle, with cattle revealing higher NH₃ reductions and a clearer trend in relationships. This is attributed to the greater attention given to feed optimization in pigs relative to cattle and also due to the specific physiology of ruminants to efficiently recycle nitrogen in situations of low protein intake. The higher NH₃ reductions in cattle highlights the opportunity to extend concepts of feed optimization from pigs and poultry to cattle production systems to further reduce NH₃ emissions from livestock manure. The results presented help to accurately quantify the effects of NH₃ abatement following reduced CP levels in animal diets distinguishing between animal types and other physiological factors. This is useful in the development of emission factors associated with reduced CP as an NH₃ abatement option.     

Freezing–thawing effects on phosphorus leaching from catch crops

It is suggested that catch crops be grown to reduce phosphorus (P) losses. However, after exposure to freezing–thawing cycles (FTCs), catch crop material can become a source of P losses to waters in moderately cold climates. This study screened potential P leaching from intact plant material of eight catch crop species: chicory (Cichorium intybus L.), cocksfoot (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), red clover (Trifolium pratense L.), phacelia (Phacelia tanacetifolia L.), white mustard (Sinapis alba L.), oilseed radish (Raphanus sativus L. oleiformis) and white radish (R. longipinnatus). The catch crops were grown in six field experiments on clay soils, where soil lysimeters (0.25 m deep) with intact crops were extracted in autumn and used for leaching experiments before and after seven FTCs in the laboratory. The eight catch crops did not reduce P leaching before FTCs. After FTCs, leachate total-P concentrations from ryegrass, oilseed radish and red clover lysimeters were significantly (p = 0.0022) higher than those from the other species and the control without a catch crop. FTCs significantly (p = 0.0064) altered total-P concentration and the proportions of different forms of P. There was a significant increase in total-P concentration in leachate from ryegrass (p = 0.0008) and oilseed radish (p = 0.02). Thus the potential risk of P leaching from ryegrass and oilseed radish material after FTCs must be considered, since they are commonly grown as nitrogen catch crops in the Nordic countries. Moreover, the roots of the tested catch crops contained 7–86 % total-P, which is important when evaluating P leaching risks.     

Influence of soil phosphorus and manure on phosphorus leaching in Swedish topsoils

In Sweden, subsurface transport of phosphorus (P) from agricultural soils represents the primary pathway of concern for surface water quality. However, there are mixed findings linking P in leachate with soil P and limited understanding of the interactive effects of applied P sources and soil test P on P leaching potential. Identifying soils that are susceptible to P leaching when manure is applied is critical to management strategies that reduce P loadings to water bodies. Intact soil columns (20 cm deep) from five long-term fertilization trials across Sweden were used in leaching experiments with simulated rainfall to explore the interactive effects of dairy cow (Bos taurus L.) manure application, soil test P and cropping system. Strong relationships were observed between ammonium lactate-extractable P in soil and dissolved reactive P (DRP) concentrations in leachate, although regression slopes varied across soils. For three soils, application of manure (equal to 21–30 kg P ha^?1) to the soil columns significantly increased DRP leaching losses. The increase in DRP concentration was correlated to soil test P, but with wide variations between the three soils. For two soils leachate P concentrations after manure addition were independent of soil P status. Despite variable trends in P leaching across the different soils, P concentrations in leachate were always moderate from soils at fertilization rates equivalent to P removal with harvest. Results clearly stress the importance of long-term P balance to limit P leaching losses from Swedish agricultural soils.     

Phosphorus feeding and manure nutrient recycling on Wisconsin dairy farms

Recently approved nutrient management regulations for livestock operations focus on a farm’s ability to recycle the phosphorus (P) contained in manure. Most efforts to improve dairy manure management emphasize manure handling, storage, and land application techniques. Little is known about relationships between dairy feeding practices and manure P levels under farm conditions, or between herd size, cropland area and a farm’s ability to recycle manure P through crops. A survey of 98 representative dairy farms in Wisconsin showed that most farms were self-sufficient in forage (alfalfa, corn silage) and grain production. Lactating dairy cows derived 90% of their feed dry matter (DM) and 78% of their P intake from these homegrown feeds. The P content (DM basis) of the dairy diet ranged from 2.3 to 8.5 with an average of 4.0g P kg⁻¹. Approximately 85% of the surveyed dairy farms fed P in excess of the recently updated National Research Council (NRC) requirements. On these farms, amounts of P in manure were related to dietary P. Of the annual manure P excreted by cows fed a diet supplement, approximately two-thirds is derived from homegrown feeds and one-third from imported mineral and protein supplements. Stocking rates ranged from 0.19 to 1.68 AU ha⁻¹. Farms having stocking rates of less than 0.70 AU ha⁻¹ are self-sufficient in feed production. Approximately half of the farms are self-sufficient in feed production, 68% produce 90%, and 80% produce 80% of their annual feed requirement. Approximately 40% of the farms have a positive P balance (manure P exceeds harvested crop P). On these farms, lowering dietary P to the levels recommended by NRC would reduce the number of farms having a positive P balance by 67%, and the land area in positive P balance by 60%. For farms having a high animal stocking rate, manure export, the addition of cropland for manure spreading, and/or reductions in livestock (cow and/or heifer) numbers may be the only feasible strategies for achieving P balance on a farm. This revised version was published online in November 2006 with corrections to the Cover Date.     

The effect of nitrogen catch crop species on the nitrogen nutrition of succeeding crops

Ten widely different plant species were compared for their ability to reduce soil mineral nitrogen levels in the autumn and their ability to improve the nitrogen nutrition of the succeeding crop. The species included monocots and dicots, crops that survived the winter (persistent) or were winter killed (non-persistent) as well as legumes and non legumes. Their ability to reduce soil mineral nitrogen content was dependent on both root depth and persistency of the crops in the autumn. For non-persistent catch crops most of the mineralization of plant nitrogen occurred during the winter, and for some of these so early as to allow leaching of some mineralized nitrogen. For persistent crops most of the mineralization occurred shortly after incorporation in the spring. The effect of the catch crops on nitrogen uptake by the succeeding barley crop varied from 13 to 66 kg N ha^–1 and the differences between the crops could not be related to any single character, but to a combination of root depth, persistency, plant nitrate accumulation, and depletion of the soil mineral nitrogen pool in spring.     

Nutrient cycling in a cropping system with potato, spring wheat, sugar beet, oats and nitrogen catch crops. II. Effect of catch crops on nitrate leaching in autumn and winter

The Nitrate Directive of the European Union (EU) forces agriculture to reduce nitrate emission. The current study addressed nitrate emission and nitrate-N concentrations in leachate from cropping systems with and without the cultivation of catch crops (winter rye: Secale cereale L. and forage rape: Brassica napus ssp. oleifera (Metzg.) Sinksk). For this purpose, ceramic suction cups were used, installed at 80 cm below the soil surface. Soil water samples were extracted at intervals of ca 14 days over the course of three leaching seasons (September – February) in 1992–1995 on sandy soil in a crop rotation comprising potato (Solanum tuberosum L.), spring wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L.) and oats (Avena sativa L.). Nitrate-N concentration was determined in the soil water samples. In a selection of samples several cations and anions were determined in order to analyze which cations primarily leach in combination with nitrate. The water flux at 80 cm depth was calculated with the SWAP model. Nitrate-N loss per interval was obtained by multiplying the measured nitrate-N concentration and the calculated flux. Accumulation over the season yielded the total nitrate-N leaching and the seasonal flux-weighted nitrate-N concentration in leachate. Among the cases studied, the total leaching of nitrate-N ranged between 30 and 140 kg ha^–1. Over the leaching season, the flux-weighted nitrate-N concentration ranged between 5 and 25 mg L^–1. Without catch crop cultivation, that concentration exceeded the EU nitrate-N standard (11.3 mg L^–1) in all cases. Averaged for the current rotation, cultivation of catch crops would result in average nitrate-N concentrations in leachate near or below the EU nitrate standard. Nitrate-N concentrations correlated with calcium concentration and to a lesser extent with magnesium and potassium, indicating that these three ion species primarily leach in combination with nitrate. It is concluded that systematic inclusion of catch crops helps to decrease the nitrate-N concentration in leachate to values near or below the EU standard in arable rotations on sandy soils.     

Effect of retention time and organic loading rate on anaerobic acidification and biogasification of dairy manure

Vast amounts of animal manure produced from concentrated animal feeding operations have the potential to be converted into economic gain if the proper processing technology is employed. Anaerobic digestion (AD) is an effective way to convert organic wastes including animal manure into profitable by‐products as well as to reduce the pollution of water, air, and soil caused by these wastes. Two‐phase AD of manure offers several advantages over conventional one‐phase AD. Solids reduction through hydrolysis/acidification might be very significant for animal manure which contains high amounts of solids. However, to date, studies of two‐phase AD of animal manure have been limited to screened manure. Therefore, this study investigated the two‐phase AD of dairy manure with particular emphasis on the effects of retention time and organic loading rate (OLR) on anaerobic acidification and biogasification of unscreened dairy manure. The results indicated that pre‐acidification of dairy manure in daily‐fed continuously‐mixed reactors with no recycle led to significantly high reduction efficiencies of volatile solids and, thus, biogas production in the subsequent methanogenic reactor especially at OLRs of 4–10 g VS dm^?3 day^?1. However, the extent of the stimulation in the biogas production relative to corresponding feed samples was quite variable (between 6.9 and 64.7%) for different solids retention times and OLR combinations. A relatively lower performance was observed for the high OLRs (20–30 g VS dm^?3 day^?1) used which was attributed to the possible wash‐out of the acidifiers at the considerably low retention times (1.25–4 days) used. Copyright © 2004 Society of Chemical Industry     

Die Verbesserung der Speckqualität von Schweinen nach Zugabe von hydriertem Seetieröl zum Futter

Improvement of Bacon Quality of Pigs after Addition of Hydrogenated Marine Animal Oil to Feed The aspects of fat supplement of pigs are discussed. Hydrogenated marine oils have in Norway been used in human nutrition for a long time. Now it has been adopted in animal nutrition as well. The first experiment made 20 years ago with bacon pigs revealed that the pork fat quality was improved by adding hydrogenated marine oil to the pig feed. The recent investigations have confirmed that the quality criteria of the bacon is better by this fat supplement. The effect is explained by the resulting change in the fatty acid composition of the pork fat.     

Rapid assessment of feed and manure nutrient management on confinement dairy farms

A basic function of dairy farming is to transform feed nutrients into milk to generate an economic return. As the price of feed grain escalates, and environmental concerns associated with animal agriculture heighten, many dairy producers seek new ways to track nutrient use on their farms. Relatively little information is available on feed and manure management under producer conditions. The present study provides an overview of an iterative process used to develop and apply techniques for rapid assessment of feed and manure management on confinement-based dairy farms in very different geographic settings. Information was collected on cow diets, milk production and manure management using rapid (2–3 h) survey techniques first on 41 dairy farms in Wisconsin, USA and then on two dairy farms in Shandong Province, China. In both locations, Holstein dairy cows (Bos taurus) transformed on average 22–30% of feed nitrogen (N) and phosphorus (P) into milk. These calculated feed N use (FNUE) and feed P use (FPUE) efficiencies corresponded well to published values, but were lower than FNUE and FPUE determined under experimental conditions. Average apparent feed N intake (range of 438–635 g cow⁻¹ d⁻¹) were slightly higher than the calculated sum of N outputs in milk (98–145 g cow⁻¹ d⁻¹) and manure (328–457 g cow⁻¹ d⁻¹). Calculated manure N excretions corresponded well to literature estimates. Average manure collection efficiencies ranged from 56% to 100% in Wisconsin and 55 to 90% in Shandong. Relatively short, face-to-face interviews can provide accurate ‘snap-shots’ of overall feed and manure management practices on an array of confinement-based dairy farms in diverse geographic locations.     

Diagnosis for ecological intensification of maize-based smallholder farming systems in the Costa Chica,Mexico

Enhanced utilization of ecological processes for food and feed production as part of the notion of ecological intensification starts from location-specific knowledge of production constraints. A diagnostic systems approach which combined social-economic and production ecological methods at farm and field level was developed and applied to diagnose extent and causes of the perceived low productivity of maize-based smallholder systems in two communities of the Costa Chica in South West Mexico. Social-economic and production ecological surveys were applied and complemented with model-based calculations. The results demonstrated that current nutrient management of crops has promoted nutrition imbalances, resulting in K- and, less surprisingly N-limited production conditions, reflected in low yields of the major crops maize and roselle and low resource use efficiencies. Production on moderate to steep slopes was estimated to result in considerable losses of soil and organic matter. Poor crop production, lack of specific animal fodder production systems and strong dependence on animal grazing within communal areas limited recycling of nutrients through manure. In combination with low prices for the roselle cash crop, farmers are caught in a vicious cycle of cash shortage and resource decline. The production ecological findings complemented farmers opinions by providing more insight in background and extent of livelihood constraints. Changing fertilizer subsidies and rethinking animal fodder production as well as use of communal lands requires targeting both formal and informal governance structures. The methodology has broader applicability in smallholder systems in view of its low demand on capital intensive resources.     

Nitrogen dynamics following grain legumes and subsequent catch crops and the effects on succeeding cereal crops

The effects of faba bean, lupin, pea and oat crops, with and without an undersown grass-clover mixture as a nitrogen (N) catch crop, on subsequent spring wheat followed by winter triticale crops were determined by aboveground dry matter (DM) harvests, nitrate (NO₃) leaching measurements and soil N balances. A 2½-year lysimeter experiment was carried out on a temperate sandy loam soil. Crops were not fertilized in the experimental period and the natural ¹⁵N abundance technique was used to determine grain legume N₂ fixation. Faba bean total aboveground DM production was significantly higher (1,300 g m^?2) compared to lupin (950 g m^?2), pea (850 g m^?2) and oat (1,100 g m^?2) independent of the catch crop strategy. Faba bean derived more than 90% of its N from N₂ fixation, which was unusually high as compared to lupin (70–75%) and pea (50–60%). No effect of preceding crop was observed on the subsequent spring wheat or winter triticale DM production. Nitrate leaching following grain legumes was significantly reduced with catch crops compared to without catch crops during autumn and winter before sowing subsequent spring wheat. Soil N balances were calculated from monitored N leaching from the lysimeters, and measured N-accumulation from the leguminous species, as N-fixation minus N removed in grains including total N accumulation belowground according to Mayer et al. (2003a). Negative soil N balances for pea, lupin and oat indicated soil N depletion, but a positive faba bean soil N balance (11 g N m^?2) after harvest indicated that more soil mineral N may have been available for subsequent cereals. However, the plant available N may have been taken up by the grass dominated grass-clover catch crop which together with microbial N immobilization and N losses could leave limited amounts of available N for uptake by the subsequent two cereal crops.     

GIS-model based estimation of nitrogen leaching from croplands of China

Nitrogen (N) is the most widely used fertilizer nutrient, and its application has increased substantially in recent decades in China. N loss through leaching has been recognized as one of the most common agricultural sources of groundwater contamination. Thus, prediction of N leaching from cropland is crucial for preventing groundwater pollution. This paper quantifies nitrogen leaching from China’s croplands, identifies its spatial distribution under current cropping systems at national scale, and finally puts forward some policies or strategies to reduce rates of N leaching. A computer process simulation model of carbon and nitrogen biogeochemistry in agro-ecosystems (DNDC) was applied to predict nitrogen leaching in the soil layer of agricultural ecosystems at national scale. Data on climate, soil properties, cropping systems, acreage, and management practices at county scale were collected from various sources and integrated into a spatial GIS database to run the model. The total amount of N-leaching was predicted at 4.57 million t N/year, which is equivalent to 48 kg N per ha cropland in 1998. The spatial distribution of N leaching in China showed a sharp discrepancy between the northern and southern counties due to the differences in climatic conditions, soil properties, as well as farm management practices. The study also suggests that applying management alternatives, such as proper fertilizer, crop, water and soil management, could be efficient means for decreasing N leaching rates.     

The prospects for integrated nutrient management for sustainable rainfed lowland rice production in Sukumaland, Tanzania

The possibilities of integrated nutrient management for sustainable ricecultivation are investigated for rainfed, lowland rice in Sukumaland,northwestern Tanzania. Typical, hardpan rice soils in Sukumaland have ratherlowlevels of organic matter, total nitrogen and available phosphorus, and a low tomedium amount of exchangeable potassium. Consumption of mineral fertilizers inrice is, however, very low due to availability problems and sharply increasedprices of fertilizers. Use of locally available resources for soil fertilityimprovement is hampered by the additional inputs of farm household labourinvolved. High labour inputs per hectare without increases in capital inputslead to lower marginal and average products per hour of labour. Furthermore, insemi-arid Sukumaland biomass production of green manures is seriouslyrestrictedby climate. The amount of kraal cattle manure is insufficient and half thehouseholds have no easy access to it. Using rice straw as cattle feed andthatching material has priority over soil fertility improvement. Some farmersindicate that at present there is not yet an urgent need for improvedintegratednutrient management in Sukumaland rice cultivation. Adoption of integratednutrient management based technologies depends on conducive socio-economic,agro-ecological and public policy circumstances. Farmer investment in learningand a favourable policy environment are thus no guarantee for worldwideadoptionof these technologies by farm households.     

Adapting feeding methods for less nitrogen pollution from pig and dairy cattle farming: abatement costs and uncertainties

This study assesses abatement costs of three measures aimed at reducing nitrogen (N) emissions from livestock production: two protein-adjusted feeding strategies for pigs, and higher-quality forage for dairy cattle. In a partial cost approach, we quantified the effect of different measures on N losses and production costs. We accounted for emissions of NH₃, N₂O and NO from animal housing, manure storage, manure application, and from soils. Uncertainties related to volatile prices and assumptions about excretion rates and emission factors were assessed in a Monte Carlo simulation. Covering variability of individual input parameters, this uncertainty assessment addresses a fundamental gap in current decision support on N loss reduction measures. For the scenarios investigated, average N abatement costs at farm level were negative and represented net benefits to farmers: In pig husbandry, adapting feeding practices in most individual situations resulted in net benefits, both for three-phase feeding (min ?35, max +5, mean ?14 €/kg N abated) and optimised single-phase feeding (min ?52, max +4, mean ?21 €/kg N abated). In dairy production, N abatement by improved forage quality proved invariably more economic than current practice (min ?40, max ?11, mean ?21 €/kg N abated). As shown in this study, N abatement costs can serve as a framework for comparing the cost-effectiveness and feasibility of N loss reduction measures within and between livestock production systems. This is in turn critical when informing practitioners and providing policy support on workable strategies for reducing the N footprint of animal husbandry.     

秸秆与猪粪混合高固厌氧消化产气性能及关键微生物分析

高固厌氧消化（HS-AD）是处理木质纤维素类原料和其他高固含率有机原料的有效方式之一。本文以节能高效为出发点，研究秸秆和猪粪为混合原料，两者不同配比（秸秆/猪粪的质量比2∶1、1∶1和1∶2）条件下，反应器的运行情况及关键微生物变化情况。结果表明：原料的配比对高固厌氧消化的产气量有明显影响。相比于其他两组实验，秸秆和猪粪的配比为2∶1时，累计产气量最大为229.66L，最终甲烷含量稳定在60.7%左右，转化为单位VS产甲烷量为131.8mL/g VS。同时，反应过程中液相性质（pH、VFA、TIC）的变化，也说明秸秆和猪粪配比为2∶1时，运行平稳且产气较好。另外，微生物分析结果显示，秸秆和猪粪配比为2∶1的实验组，在实验启动的前期，甲烷八叠球菌（Methanosarcinaceae）的相对丰度较高，并且细菌和古菌群落的丰富度和多样性都优于其他两组。     

Short-term carbon dioxide emissions and denitrification losses from soils amended with low-P manure from genetically modified pigs

Genetically modified pigs have been developed that are able to use phosphorus (P) in the feed more efficiently and thereby reduce the amount of P excreted in the manure. Improved digestibility would also change the chemical composition of the manure. The objective of this study was to determine how improved P digestibility affects the manure composition and the associated carbon dioxide (CO₂) emissions and nitrogen (N) loss through denitrification when the manure is applied to soil. Aerobic and anaerobic incubation studies were conducted to evaluate CO₂ emissions and denitrification losses from two soils (Brookston clay loam and Harrow sandy loam) amended with pig slurry (115 mg N kg⁻¹ soil) from transgenic pigs as well as from conventional pigs. In addition, both the transgenic and conventional pigs were fed either a low-P diet or a conventional P diet, and the effects of diet type on CO₂ emissions and denitrification losses were examined. Carbon dioxide emissions were 17% lower (P < 0.05) in treatments amended with transgenic pig manure compared with conventional pig manure in the clay loam soil. However, denitrification losses were increased by 37% (P < 0.05) in the clay loam soil amended with manure from transgenic pigs compared to manure from conventional pigs. Neither CO₂ emissions nor N loss through denitrification were affected by pig genotype when the manure was added to the sandy loam soil. The diet type (conventional P diet or low-P diet) did not affect either CO₂ emissions or N losses through denitrification in either the Brookston clay loam or Harrow sandy loam soils.     

发酵饲料的应用及其对环境的影响

当前,畜禽养殖中大量使用饲用抗生素并产生大量畜禽粪便,对环境构成了巨大威胁,也严重制约了我国畜牧业的可持续发展。发酵饲料的应用有望改变当前养殖困境,减少乃至不使用饲用抗生素,提高饲料利用率,减少氮磷排放和氨气、硫化氢等有害气体的排放,降低锌、铜等重金属的添加,最终缓解畜禽养殖对环境的污染。简述了发酵饲料的应用及其对环境的影响,为发酵饲料的开发和应用提供支撑。     

Inorganic N Dynamics from Soils Amended with Low-P Manure from Genetically Modified Pigs (EnviropigTM)

Genetically modified pigs have been developed to enable them to use phosphorus (P) in the feed more efficiently and thereby reduce the amount of P excreted in the manure. However, there is no information available about how improved P digestibility affects nitrogen (N) and carbon contents in the pig manure and the subsequent dynamics that occur when the manure is applied to soil. An 8-week incubation study was conducted to determine the changes in inorganic N contents of two soils (a clay loam and a sandy loam) treated with pig manure (115 mg N kg⁻¹ soil) from these transgenic pigs as well as from conventional pigs. In addition, both the transgenic and conventional pigs were fed either a low-P diet or a conventional P diet and the effects of diet type on N contents in the manure and the subsequent soil dynamics were examined. There was no difference in total manure N content between transgenic and conventional pigs. However, the ammonium content was lower and the soluble carbon level was greater in manure produced by transgenic pigs than by conventional pigs. The manure excreted by pigs fed with low-P diet contained more total N and ammonium N than the manure from pigs fed with conventional-P diet. Ammonium-N was nitrified completely in the first week of incubation in manure-amended clay loam, while the nitrification process took 4 weeks to complete in manure-amended sandy loam soil. Manure from transgenic pigs not only contained less inorganic N but this N was more rapidly immobilized and/or denitrified compared to the inorganic N produced by conventional pigs.