Due to the existence of interactions between crops, pasture and livestock, crop-pasture rotations are more complex systems to model compared to continuous cropping rotations. The inclusion of a “long fallow” phase that interacts with both crops and livestock further increases this complexity. This paper explains a linear programming model developed by the Victorian Department of Natural Resources and Environment. The model represents the mixed grain/sheep farming system of the Victorian Mallee region where crops are rotated with annual legume pasture and “long fallow”. Model runs have highlighted important issues in relation to the objective of profit maximisation and the trade-off against risk management by farmers.