Nitrogen rate influences on protein concentration, yield, and NDVI in spring wheat following pea and cover crop mixture

Abstract High‐protein wheat ( Triticum aestivum L.) grain is useful for bread flour, and normalized difference vegetation index (NDVI) can be useful in predicting crop yields and assessing overall crop health in response to a wide variety of management systems. However, protein and NDVI responses to nitrogen rates in systems containing cover crops have been understudied in spring wheat. Protein, grain yield, and NDVI measurements were collected during the spring wheat phase of spring wheat–pea ( Pisum Sativum L.)/cover crop rotations in different plots in 2018 and 2019 at the Northern Great Plains Research Laboratory, Mandan, ND. Grain protein concentration increased with nitrogen (N) rate, but not every level of N rate was significantly different. This result suggests that preceding pea then cover crop mixture can slightly reduce the nitrogen fertilizer requirements of subsequent spring wheat. Spring wheat NDVI did not significantly respond to categorical nitrogen rates, but continuous N rate had a small positive effect. Adding NDVI heterogeneity (as measured by the nugget:sill ratio) improved peak NDVI‐based spring wheat grain yield predictions at the relatively small scales that were measured.