Abstract
BACKGROUND AND PURPOSE Fertility management remains one of the most crucial aspects of organic production systems; there is a reliance on legume derived nitrogen but long term fertility building leys are expensive, particularly in stockless systems when they give no direct economic return. Soil nutrient management and improvement of fertility building strategies has been identified as priority for research (ACOS, 2006). Because of their multifunctionality the choice of fertility building cropping has implications on soil structure and subsequent weed, pest and disease problems as well as on soil nutrient dynamics. Long term monitoring work is essential if the full effects of contrasting approaches are to be evaluated. OBJECTIVES AND APPROACHES Objective 1) To continue to monitor the agronomic and economic effects of three established stockless fertility building strategies for arable and vegetable crops. The experimental area at Hunts Mill (Warwick HRI, Wellesbourne) has been closely monitored since conversion to organic management began in 1995. This was done within DEFRA projects Conversion to organic field vegetable production (OF0126T and OF0191) and Baseline monitoring of organic vegetable systems (OF0332). Further information about these projects can be found at http://www2.defra.gov.uk/research/project_data/Default.asp. Both field vegetables and arable crops are grown with three cropping strategies which are contrasting with respect to the proportion of time dedicated to fertility building and the species of fertility buiding crops which are used. Monitoring the performance of these strategies will be continued by assessing yields of cash crops, offtakes of nutrients in harvested crops, returns to the soil of plant residues from cash and fertility building crops, soil nutrient and organic matter status, incidence of weeds, pests and diseases and economic performance.The data collected from the point of conversion onwards will be combined with that obtained in the new study. The site will continue to be available as a resource for additional research projects. Objective 2) To capture existing information about fertility building crops held by farmers and other experts. A stakeholder meeting will be held with the purposes of pooling the existing knowledge, confirming the species to be studied selecting suitable on-farm sites and to encourage farmer engagement in the project. Objective 3) To assess the performance of a range of novel legumes (fertility building crops and cash crops) on several sites and to asses their impact on subsequent crops. The performance and subsequent effects (on cash crops and soil nutrients) of single species and species mixtures will be evaluated using both simple on farm trials on at least six sites (to gain information under realistic farming conditions) and replicated experiments which will permit more detailed monitoring to be conducted. The replicated work will be done on part of the Hunts Mill area of Warwick HRI. Objective 4) To determine the usefulness of three computer models developed recently for assessing the nitrogen dynamics of organic rotations, specifically with regard to nitrate leaching. The models selected have been developed with specific relevance for organic systems (the EU-Rotate-N model, the FBC model developed as part of Project OF 0316 and the Dutch NDICEA model). Further validation of the EU model will be conducted by comparing simulations with measured data. The other models will be used as tools to assess the agronomic, economic and environmental effects of various fertility building strategies under a wider range of weather and soil conditions than would be possible to do using field work. Objective 5) To interpret the new data within the context of whole farm systems to assess the implications of organic farming on soil fertility. The implications of different fertility management approaches on the long term sustainability of various organic farming systems will be considered - this will build on previous work and consider soil fertility in its widest sense. Objective 6) To disseminate the findings of the project through a number of channels. Regular communication events will be arranged, mainly field based on the experimental sites. Articles will also be written for the farming press and presented at appropriate conferences and on websites. Papers will be written for peer reviewed journals and an advisory booklet will be produced. This project will be led by HDRA working in collaboration with Warwick HRI, ABACUS Organic Services, OAS EFRC, IGER. The project will be guided by a steering committee. BENEFITS This project is of direct relevance for organic farmers. It aims to provide information to help with rotation design to maintain the balance between fertility building and exploitative cropping whilst maximising financial returns and minimising adverse environmental effects. Improved scientific understanding and knowledge in this area will also be of benefit to other stakeholders eg policy makers and regulatory bodies.
United Kingdom