ECONOMIC IMPORTANCE OF MANAGING SPATIALLY HETEROGENEOUS WEED POPULATIONS

Three methods of predicting the impact of weed interference on crop yi eld and expected economic return were compared to evaluate th economic importance of weed spatial heterogeneity. Density of three weed speci es was obtained using a grid sampling scheme in 11 corn and 11 soybean fields. Crop yield loss was predicted assuming densities were homogen eous, aggregated following a negative binomial with known population m ean and k, or aggregated with weed densities spatially mapped. Predict ed crop loss was lowest and expected returns highest when spatial loca tion of weed density was utilized to decide whether control was justif ied. Location-specific weed management resulted in economic gain as we ll as a reduction in the quantity of herbicide applied.