Directed RX: A Novel Method for Developing Site-Specific Prescriptions

Abstract. Directed R_X is a method developed by Clemson University researchers in an effort to optimize zone delineation and assignment of inputs for spatially variable prescriptions. Currently employed methods of variable rate prescription development generally assign rates or products (e.g. hybrids) to pre-defined yield management zones, with a number of studies focused on how to best define these management zones. The rates and products assigned are often based on data generated from conditions not represented in the field for which the prescription is made. Check strips or blocks in conventional prescription assessment allow for adjustment of rates within zones but do not allow for zone boundary refinement. The Directed R_X method uses strip tests to spatially integrate yield and therefore profit with site-specific foundation (e.g. soil EC, elevation, and irrigation) polygons, resulting in optimized prescriptions, specific to a field and input. The method allows for layering of multiple datasets for zone foundation and is applicable to prescription development for any input where yield data is available. Tests conducted in 2016 demonstrate potential benefits of the method from case studies in variable rate corn seeding (3-19 USD ac^-1), dual hybrid corn seeding (2-18 USD ac^&-1 above variable rate seeding benefit), variable rate soybean seeding (6 USD ac^-1), and variable rate nitrogen for cotton (11 USD ac^-1). The Directed R_X method requires one year of production to develop the prescription, which can be applied in the following production year. By design, the method puts producers‘ yield data to work in optimizing their prescription plans for maximum profitability.