摘要:

Under field conditions a crop of Brussels sprouts (Brassica oleracea, var.gemmifera) usually utilises the plant-available nitrogen better than leeks (AlliumporrumL.). To investigate the role of the root system in nitrogen utilisation, the two crops were grown in the Wageningen Rhizolab, a new rhizotron facility. Large differences in rooting pattern were observed. Leeks had a relatively shallow rooting system with maximum root growth at a depth of 15 to 20 cm and a low rooting intensity. The rooting pattern of Brussels sprouts could explore the soil profile to a depth of one metre in a very short period. Large differences in nitrogen uptake pattern also showed up between the crops. Brussels sprouts depleted the entire rooted profile of nitrogen in a relatively short period (June to mid-August) whereas in leeks the nitrogen uptake was greatest in the second part of the season. The implications of these rooting and nitrogen uptake patterns for fertilisation management strategies to minimise N losses in ecological farming are discussed.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754709

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Estimates of nitrate leaching derived from porous ceramic cups and soil analysis were compared in the winter of 1992/93 on farms within UK Pilot Nitrate Sensitive Areas. In these areas farmers have modified crop management with the aim of reducing nitrate losses to groundwater. These changes are relevant to ecological agriculture. The fields studied contained a range of arable crops, including cover and catch crops, and grass. Autumn soil mineral nitrogen to 90 cm (SMN) was highly correlated with estimates of leaching derived from porous cup samples, especially under arable crops. Correlations with the change in SMN over winter were less good and more affected by cropping situation. They were especially poor on grassland. These discrepancies were attributed to mineralisation of soil N and crop uptake during the leaching period. The effects of crop, soil and weather interactions on patterns of nitrate loss are discussed. The use of porous cups is preferred to SMN for estimating leaching since it avoids the need to allow for N transformations and is therefore more precise, especially when leaching losses are small.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754710

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The paper describes a mesocosm (pot) experiment which provides the possibility for multiparametric evaluation of N-flows required for an ecological approach to N-cycIing in a soil/plant/atmosphere system. The quantitative distribution of nitrogen between different pools is presented and particular emphasis is given to the contribution of soil mesofauna. The determination of a wide spectrum of cumulative N-flows (soil-N in NO3−, NH4+and active organic pools, plant uptake, mesofaunal N-content, gaseous N-losses) indicates the change of N- transformation dynamics which may be studied by supplementary testing of microbiological and mesofaunal activity joint to the basic experimental model.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754711

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Nutrient provision for plants in organic farming systems is mainly based on the use ofon-farm sources, i.e. farmyard manure, handled by different techniques, urine and slurry;off-farm sources, i.e. different composts and mineral or organic fertilizers; and the integration of leguminous andnon-leguminous plantsin the crop rotation.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754712

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The different ratios of organic to inorganic nitrogen of organic fertilizers affect the nitrate dynamics in soil as well as the yield of crops. To examine this, winter wheat was cultivated on loess in Therwil near Basel (Switzerland). The plots were amended with stacked, composted and rotted manure, garden waste compost, slurry or mineral fertilizer (mineral control). In additional treatments, a top dressing with slurry was applied. Nitrate concentration in soil water was measured with ceramic cups. The N uptake of winter wheat was determined at three growing stages: tillering, flowering and at harvest.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754713

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Twenty-five 200 L lysimeters were filled with a sandy soil and used to compare five fertilisation regimes (5 replicates): unfertilised control, manure compost, urban compost, brushwood compost and mineral NPK, with comparable nitrogen supplies. Crops (mixed grass, wheat, carrot, lettuce, wheat, lettuce, wheat, vetch-oats) were grown successively during five years and nitrates leached under the soil were continuously collected and quantified monthly. The overall amount of nitrates leached under crops was in the following decreasing order: mineral NPK, manure compost, urban compost, control, brushwood compost. The highest yields were obtained with manure compost and mineral NPK. The present data thus demonstrate the high efficiency of manure compost and the beneficial reduction of nitrate leaching elicited by organic fertilisers during a five year rotation.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754714

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

During storage and decomposition of solid manure, gaseous and leaching nitrogen losses occur which contribute strongly to the debit side of nitrogen balance-sheets of ecologically managed farms. Gaseous as well as leaching losses are highest at the beginning of the decomposition and decrease with time. Both are affected by temperature, strawrfaeces-ratio, pH, initial N-content and heap rotation.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754715

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

European Community legislation will require controls upon agriculture to reduce nitrate leaching. A voluntary pilot Nitrate Sensitive Area (NSA) Scheme to assess the impact of changed husbandry practices on nitrate leaching has been in operation in England for three years. It is proposed to expand it in 1994 under the EC Agri-Environment Regulation. Research findings have shown that livestock manures applied in autumn and early winter increase nitrate leaching from both arable and grassland. Cover crops reduce the loss of nitrate. The initial loss from straw- based manures is less than from slurries and poultry manure. The original proposals for the future NS As included limits on the use of all manures which could have prevented organic farms from participating in such schemes. These plans have been modified in a way which will allow many organic systems to join the Scheme but not outdoor pig or poultry units. Organic farmers hope that when Vulnerable Zones are delineated under the EC Nitrates Directive the Action Plans will allow their organic systems to continue.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754716

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In October 1993 an international workshop on nitrogen leaching in ecological agriculture was held at the Royal Veterinary and Agricultural University in Copenhagen, Denmark. This paper summarizes the discussion at the workshop and outlines recommendations and conclusions. The paper identifies key factors of major importance to a consideration of nitrogen leaching from ecological agriculture. These are: the farming systems approach: management of nitrogen resources at the farm and field level; the research methodology adopted to study nitrogen leaching; and finally the need to consider the problem of nitrogen leaching from a rotational perspective taking account of the heavy reliance on N fertilizers of conventional systems, which in turn leads to environmental, social and ethical problems. It is recommended to emphasize research work aimed at improving and developing ecological farming systems, in order to improve the ability of ecological agriculture to meet defined agronomic, economic, environmental, social and ethical criteria. Furthermore, it is recommended to encourage initiation of research in nitrogen supply and cycling in ecological farming systems and to organize further workshops aimed at intensifying cooperation and exchange in research work. It is concluded that there is a considerable potential for ecological farming systems to offer a viable approach to limit nitrate leaching whilst also meeting the requirements of broader goals of sustainability.

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754717

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1995.9754688

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor