Fertilizer Nitrogen Rate Prescription, Interpretational Algorithms, and Individual Sensor Performance in an Array

Many sensors require algorithms/mathematical functions to translate measurements into practical outcomes. In arrays (sensor groups), the agronomic consequences of variations in individual unit performance, while driving an algorithm, remains uncharacterized. Our objective was to study the performance of individual active canopy reflectance sensors outputting normalized difference vegetative index (NDVI) data, used to prescribe the corrective N fertilization rate for winter wheat (Triticum aestivum L.). We hypothesized that sensor output differences would influence corrective N prescriptions when the NDVI data were interpreted with the usual discontinuous, “stair‐step”, algorithms. The NDVI data from an eight‐sensor GreenSeeker array (Trimble Navigation Limited, Westminster, CO) were obtained at growth stage Feekes 6 for four wheat fields. Individual sensors were coupled with individual liquid N application nozzle sets, and operational settings make possible the independent fertilization of each 0.56 m2 of field area. Two algorithms (A and B) were evaluated. We observed large differences in individual sensor corrective N prescriptions, despite little short range (