Strategies to encourage better use of nitrogen in animal manures

Research conducted in the MAFF Nitrate Programme has been used to formulate new and improved guidelines on the efficient use of manure nitrogen (N). I n order to reduce nitrate leaching losses, manures containing large amounts of available N (i.e. slurries and poultry manures) should not be applied t o free-draining soils in the period from autumn to early winter. Also, for efficient nutrient utilization manure application rates should be consisten t with agronomic requirements (up to 250 kg total N ha(-1) yr(-1)). Existin g farm machinery was shown to be capable of applying manures evenly to gras sland and arable stubbles, but required an accurate estimate of application rate and the careful matching of spreading widths. To provide growers with detailed guidance on the fertilizer N replacement value of manures the com puter-based decision support system MANNER (MANure Nitrogen Evaluation Rout ine) has been developed. The much improved understanding of manure N losses and availability has been summarized in a series of 'Managing Livestock Ma nures' booklets, the MAFF Fertilizer Recommendation booklet and the Codes o f Good Agricultural Practice.