New Approaches to Nutrient Management in Organic Farming
This session, chaired by Christine Watson from the SAC, explored how new research results contribute to improving nutrient management for food and feed crops in organic systems. Excellent presentations from Francis Rayns (Garden Organic) and Robin Walker (SAC) discussed results from a number of trials investigating a range of management approaches to N and P availability, while Liz Stockdale (Newcastle University) used a novel approach involving chocolate, toffees and delegates to demonstrate K availability in soils. Discussion focused on the practical implications of these research results for producers.
This session, chaired by Christine Watson from the SAC, explored how new research results contribute to improving nutrient management for food and feed crops in organic systems. Francis Rayns, from Garden Organic, described their long-term stockless Hunts Mill experiment, where the effects of three fertility-building strategies (one year leys, two year leys, and 6 month green manure crops only) on crop yields, nutrient budgets, soil organic matter and economic performance were investigated. As expected, there was more plant-available N in the 2-year ley plots, while the use of a green manure was unpredictable due to establishment issues. Francis stressed the importance of considering the timing of nitrogen availability rather than concentrating solely on total N, in order to optimise crop yields and minimise leaching.
Robin Walker, from SAC, reported on trials investigating a range of approaches used to increase P availability to crops from rock phosphate. These included harnessing biological processes such as the crop’s own ability to liberate P and co-composting of rock phosphate with organic wastes to optimise P release through microbial processes; and rotational aspects such as the establishment of autumn sown green manures, and the use of spring sown crops chosen for their ability to liberate P and use it themselves as well as for potential benefits to subsequent crops. Robin highlighted that some crops, including buckwheat and brassicas, are better than others at accessing P from rock phosphate and that rotational effects on P availability can be positive. Liz Stockdale, from Newcastle University, rounded off the workshop with some audience participation involving chocolate and toffees to demonstrate the action of K ions in sandy loam and sandy clay loam soils, and highlighted the importance of organic matter in potassium retention. She discussed management issues including the value of regular K analysis to give a good indication of plant-available K, how cutting crops while green removes more K than senesced crops and how grass-clover accumulates more K than it needs so that continuous silage may deplete soil K.