Spatial inference of herbicide bioavailability using a geographic information system

This article presents an approach to managing and evaluating soil survey data that can aid in soil-applied herbicide decision making. Field experiments were used to quantify the dose responses of corn, shattercane, and velvetleaf to isoxaflutole over a range of soil conditions within an agricultural field. Isoxaflutole doses eliciting crop injury (20% greenness reduction) and weed control (80% biomasss reduction) were projected for a county located in Nebraska based on associations between the plant response and the soil properties. The biologically effective dose of isoxaflutole increased with increasing organic matter and mineral surface area. Mean biologically effective doses for velvetleaf (1 to 27 g/ha) were considerably lower than that for shattercane (42 to 206 g/ha). Over 60% of the surface texture is silty clay loam for Saunders County, suggesting that 17 and 158 g/ha are the minimal doses required to suppress velvetleaf and shattercane, respectively, for a majority of the county. Conceivably, this approach could be used as an initial step to assess the relative value of field-specific applications and variable dose application technologies.