Cropsyst-Microbasin Model As a Tool to Inform Variable-Rate Nitrogen Management and Dryland Farm Profitability.

Precision fertilizer management is a promising method to maintain high agricultural yields while using less fertilizer inputs in the highly heterogeneous Palouse region. This study assessed the use of CropSyst-Microbasin at a tool to inform fertilizer management practices.  A highly-instrumented field site was used to parameterize CropSyst-Microbasin; the model accurately simulated spatial and temporal changes in soil water content, total surface runoff, and average crop yield. Fertilizer management scenarios were conducted with an analysis of total nitrogen loss, crop yield, and farm profitability. Simulated yields were analyzed with local costs of production and varying crop, fertilizer, and fuel costs to examine the sensitivity of profitable fertilizer management to varying market conditions. Hillslope scenarios demonstrate the capacity of CropSyst-Microbasin to simulate the contribution of lateral redistribution of nitrogen to down-slope yields. Field catchment (roughly 10 hectare) simulations demonstrate the unique capacity of CropSyst-Microbasin to simulate agricultural production on highly heterogeneous landscapes, capturing spatial and temporal variability. Simulations and field sites were examined in conjunction with other types of production measurements, such as NDRE-based N uptake predictions, to explore field-scale spatial and temporal drivers of production and risk to inform precision fertilizer management on the Palouse.