The spatial variation in crop yield, and the field-based factors that contribute to it, is developing as a subject of importance to both the farming and wider communities. Increasing attention is being focused on the notion that agricurally productive land can be managed as a relatively homogeneous unit at the 'within-field' scale. Such an assumption may lead to inappropriate resource application and associated financial, environmental and social costs. The significance of these imposts, such as input waste, yield reduction and soil, water and air contamination has been identified in the Cotton Research and Development Corporation (CRDC) publications compiled by Anthony et al. (1992) and Hearn (1993). Preliminary research has prompted the proposal of site-specific management as a remedy to many of these environmental and resource-use inefficiency problems (Larsen & Robert 1991). Figure 1 outlines the simple rationale that justifies and supports site-specific management