Managing uncertainty in site-specific management: What is the best model?

Models which enable the representation of spatially variable crop performance are central to site-specific management. Rarely have these models been considered in relation to the different sources of uncertainty facing the decision maker. This paper describes various sources of uncertainty (temporal, metrical, structural, and translational) in the context of the site-specific management problem and the model types proposed to solve the problem. An example involving the site specific application of nitrogen fertilizer in dryland wheat production is presented to show how these model types might be evaluated for suitability to a given situation. We conclude that in data poor situations, knowledge-driven models may be less accurate but preferred by the farmer, while in data rich situations data-driven models may be more appropriate.