Integrating soil-based management zones (MZ) with crop-based active canopy sensors to direct spatially variable N applications has been proposed for improving N fertilizer management of corn ( Zea mays L.). Analyses are needed to evaluate relationships between canopy sensing and soil-based MZ and their combined potential to improve N management. The objectives of this study were to: (i) identify soil variables related to in-season crop canopy reflectance and yield and use these variables to delineate MZ for N fertilizer management; and (ii) compare corn yield response to different N fertilizer treatments for different MZ. Eight N rates (0-274 kg N ha -1 in 39 kg ha -1 increments) were applied in replicated small plots across six irrigated fields in 2007 to 2008 throughout central Nebraska. Soil variables evaluated for MZ delineation included: apparent soil electrical conductivity (EC a), soil optical reflectance, and landscape topography. Crop response to N was determined via active sensor assessments of in-season canopy reflectance (chlorophyll index, CI 590) and grain yield. Relationships between soil and topography data and crop performance were evaluated, with selected soil variables used to delineate two MZ within four of the six fields. Economic benefits to N application according to soil-based MZ were observed in fields with silty clay loam and silt loam soils with substantial relief and eroded slopes. Sensor-based algorithms may need to be adjusted according to MZ to account for differences in crop N response.
