Modelling crop physiology for integrated decision making

Crop modelling has had a mixed press over the years, driven as much by the community's expectations as by the targets identified by modellers. This short review gives a personal perspective on the scope and value of models of crop processes and performance, in the context of the increasing demand to make predictions about the best course of action for farmers. The goal for these predictions can range from the best rate or timing for a pesticide spray to the likely pressure on the farming community if predicted levels of climate change are realised. The primary conclusion is that a clear statement of objectives is the most important precursor to the use of models of crop processes or systems.