A preliminary approach to assessing the opportunity for site-specific crop management in a field, using yield monitor data

This paper proposes an Opportunity Index (O_i) for site-specific crop management (SSCM). In contrast to the traditional practice of uniform agronomic management, SSCM aims to match controllable inputs with spatially variable crop requirements. Farmers, however, are often left wondering how their yield maps can be used to justify a change to SSCM. The O_i is a single number that may be used in the process of this justification. The O_i is based on three components: (1) the magnitude of variation present in a yield map, relative to a certain threshold; (2) the average area within which yield is autocorrelated, relative to the minimum area within which variable-rate controllers (which physically implement SSCM) can reliably operate; and, (3) the economic and environmental benefit of SSCM relative to uniform management. The O_i was calculated for 20 Australian cropping fields and compared with b′ [Journal of Agricultural Sciences, Cambridge, 28 (1938)], which is an alternative method of quantifying the management opportunity from yield variation. A weak negative correlation was found to exist. Results suggest that a good opportunity for site-specific crop management exists when the O_i is greater than 20, although this is only a tentative recommendation.