摘要:

The characteristics of organic farming involve the application of husbandry practices which are consistent with limiting nitrate leaching from agricultural land. The high losses of nitrate associated with ploughing of grass-clover leys are balanced by lower losses during the subsequent years of the arable and grassland phases of the rotation.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754699

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The fundamental processes that influence nitrate leaching are similar in all farming systems and research into the processes operating in conventional agriculture also contributes to an understanding of N cycles in organic farming. Many of the strategies that have been proposed for reducing N leaching in conventional agriculture are also applicable to organic farming. The relevance of much research to organic agriculture is limited by differences in the organic matter content and biological activity of organically and conventionally managed soils with the result that quantitative information about organic systems cannot always be derived from conventional agriculture. There is a particular need for information about N fluxes in whole-farm systems, particularly those involving grass/arable rotations.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754700

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In four year field trials faba bean cultivation techniques were tested with the primary aim to reduce nitrate losses via leaching by increasing crop soil-nitrate uptake. This aim did not generally contradict the aims of gaining high faba bean grain yields, high amounts of symbiotically fixed nitrogen and an increased precrop effect. As a function of poor rooting systems and poor soil-nitrate uptake faba bean pure stands left high amounts of nitrate in the soil before winter, which is suspected to be leached during winter. A more homogenous rooting-distribution via narrow faba bean row distances increased soil-nitrate uptake and slightly reduced residual- nitrate content before winter. Increasing crop rooting-density by intercropping with cereals or undersown non-legumes considerably reduced soil residual-nitrate content. Undersown brassicas like oil-radish or white mustard were more efficient than ryegrass and intercropping with cereals. Undersown crops showed no negative effect on faba bean grain yield and N2-fixation. Intercropping with cereals considerably reduced faba grain yield and N2-fixation. Underseed variety in faba beans and intercropping considerably affected precrop effects to the successive crop oats as a function of different amounts and temporary availability of nitrogen.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754701

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In field experiments at six different sites in Sweden, leeks ere fertilized with farmyard and green manures. The sites were both at farms with ecological vegetable production and at research stations of the Swedish University of Agricultural Sciences. Two of the manures were combined with raised beds and mulching with black plastic film and grass/legume material in order to study the effect of these management practices in relation to the effects of the manures on N availability. Net N mineralization was determined by measurements of N uptake in leeks and of changes in mineral N content in the soil.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754702

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The soil content of mineral nitrogen to 1 m depth has been measured several times in the leaching period on 600 conventional agricultural fields in a SQUARE GRID with a side length of 7 km. The measurements were also carried out in 26 ecological fields. Information on management practice was collected every year and soil physical parameters were determined. The soil content of mineral nitrogen in autumn was compared. Furthermore the nitrate leaching values were calculated in most of the conventional fields and in nine of the ecological fields by means of the DAISY nitrogen model.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754703

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Recent findings concerning nitrogen cycling and dynamics are discussed. Ruminants excrete most of the N intake in urine, from which it is easily lost. By proper management of liquid manure in the case of loose housing, losses can be reduced to about 10% of excreted nitrogen. The same reduction can be reached in stanchion stables with straw. Deep litter systems result in greater losses. Catch crops are able to take about 2 kg N day−1and after incorporation the release of nitrogen starts almost immediately. The mineralisation of nitrogen can be estimated for each addition of organic matter. The weather pattern and the timing of soil tillage have a strong influence on the speed of mineralisation. Physical and morphological properties of soil influence the leaching of nitrogen. By-pass flow may reduce leaching from the sub-soil and speed it up from the top soil. The nitrogen fixation capacity of grass clover mixtures is high and allows severe losses without affecting the production level of the farm. Management supporting models can be used to generate ideas about the nitrogen management of arable land. The management of the nitrogen in grassland is often complicated due to temporary lability of the composition of grass/clover mixtures. Losses by leaching can be reduced by making silage in autumn and by balancing the feed.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754704

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Symbiotic nitrogen fixation by legumes is the main input of nitrogen in ecological agriculture. The cycling of15N-labelled mature pea (Pisum sativumL.) residues was studied during three years in small field plots and lysimeters. The residual organic labelled N declined rapidly during the initial weeks of decomposition, due to high rates of residue N net mineralization and subsequent leaching and denitrification losses of N. Lysimeter experiments showed that pea residues may reduce leaching losses of N, probably due to their effect on the mineralization-immobilization turnover of N and denitrification. Winter barley succeeding field pea recovered 13% of the incorporated pea residue N by early December; the recovery was found to be 15% at maturity in July. A spring-sown crop of barley recovered less than half the amount of pea residue N recovered by winter barley. The residue N-use efficiencies were 36% and 15% in three sequences of cropping systems with autumn- or spring-established crops, respectively. The results highlight the requirement for establishment of crops after cultivation of pea which are efficient in taking up N in the autumn/early spring and the need for improved residue management methods in order to conserve grain legume residue N sources within the soil-plant system.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754705

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A correct estimation of the amount of biologically fixed atmospheric derived nitrogen (N) is important for evaluating the environmental impact of a clover-grass system.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754706

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The cycling of nitrogen in agroecosystems is influenced by the amount and quality of organic matter applied to soils. The N-mineralization of15N-labelled ryegrass (Lolium perenneL.) was significantly slightly higher in a soil with long-term application of a high amount of farmyard manure (FYM) than in soils receiving either mineral fertilizer, a low amount of FYM or no manure. However, in general the decomposition of ryegrass in the selected soils varied only slightly. The microbial decomposition processes differed somewhat in the soil manured with a low amount of FYM from those receiving other manure treatments.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754707

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Plant N uptake and mineralisation were studied in a pot experiment using two soils of contrasting textures with a range of15N-labelled manures: poultry manure, cattle slurry, fresh swine manure, composted cattle manure, sewage sludge, straw, cabbage residues, pea residues and grass-clover turf. A range of manure and soil properties were determined before the incubations to examine if any combination of these properties would be useful to predict the amount and timing of N supply. Three replicate pots with and without ryegrass were used. Soil mineral nitrogen and ryegrass yield, N uptake and15N enrichment were measured throughout the 16 week incubation.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754708

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor