Perspectives on nutrient management in mixed farming systems

Summary

Changes in agricultural subsidies in Europe and the ready availability of fertilisers have allowed a spatial decoupling of livestock and crop production. This has increased the flow of nutrients that occurs between farms compared to within individual farms. In terms of nutrient cycling mixed farms provide the opportunity to re-integrate aspects of agricultural production. The degree of integration between crop and livestock production is defined by the reliance on the use of home-produced feed compared to imported feed, and is independent of intensity. Farm scale nutrient use efficiency (NUE) is inversely related to stocking density. Management of inputs and/or internal flows offers the scope to improve NUE on mixed farms. Greatest uncertainties in calculating NUE are associated with variation in yield and composition of home produced feed and consequent manure composition. Three key areas are addressed here 1) the role of livestock diet in manipulating the amount and availability of manure nutrients 2) the impact of manure management on nutrient losses and 3) nutrient management through the integration of crops and livestock in rotations. While not all the associated issues are unique to mixed farming these three areas all influence NUE.