Modelling the determinants of grassland stocking rates on dairy farms in England and Wales

An attempt has been made to provide a quantitative model of grassland management on a dairy farm which could be used for predictive purposes to establish appropriate stocking rates in relation to the resources available and the consequences of changing the level of resources used. The model takes into account the effect of rainfall, the available water capacity of the soil, soil drainage and fertiliser usage on grass production and the calving pattern, milk yield and availability of other feeds in determining grass requirements. Allowance is made for the fact that the response to unpredictable variation in grass production may be to under-stock. There was reasonably good agreement between predicted and actual stocking rates for a group of 33 dairy farms, but the predictions were too variable for acceptance of the model as a reliable aid in management planning on individual farms. Nonetheless, the model showed sufficient promise to suggest that it may be feasible to make predictions for individual farms in the future if a clearer understanding of a number of aspects of grassland management can be obtained: most notably, how farmers respond to risk, how managerial ability and financial constraints affect stocking intensity and how farmers integrate, in practice, grazing and conservation.