Introduction of seasonal and spatial specification to grass production andgrassland use in a dairy farm model

A linear programming model of a dairy farm, in which grass production and g rassland use was originally modelled using one growing period and one area of land, is extended. To include seasonal and spatial elements of variation not allowed for in the original model, the model was modified to reflect t hree growing periods in the season and then to reflect management of two se parate areas of land. The resulting three models were used to assess farm p hysical planning, economic results and nutrient balances for an average Dut ch dairy farm in a situation without and with levies on nutrient surpluses. It is concluded that incorporating seasonal and spatial elements provides greater insight into grassland management. Seasonal model specification doe s not result in significant changes in farm physical planning, income and n utrient surpluses. Spatial specification has a larger impact if one of the two areas cannot be grazed by dairy cattle.