Nitrogen and water impacts on hard red spring wheat (Triticum aestivum) yield, quality, canopy reflectance, and income in South Dakota

anopy reflectance, commonly known as remote sensing, offers a simple, time efficient method for making in-season nitrogen (N) recommendations for hard red spring wheat (HRSW, Triticum aestivum). However, spectral crop reflectance can be confounded by water and N stress that simultaneously impact protein content and yield. The objective of this study was to determine the impact of water and in-season N applications on HRSW yield, quality, canopy reflectance and economic returns in mixed and tallgrass prairie ecoregions of South and North Dakota. At three locations, a range of N rates and applications timings were implemented and canopy reflectance, yield, protein, and yield loss due to N (YLNS), and water stress (YLWS) were measured. Remote sensing-based prediction models were developed based on canopy reflectance. Economic returns for a variety of economic scenarios were determined.;Research findings showed that in the tallgrass prairie ecoregion: (1) YLNS decreased with increasing N fertilizer whereas YLWS increased; (2) protein concentration generally increased with N addition; (3) regression models between canopy reflectance and yield, grain protein, and YLNS at explained the greatest variation at Haun 6; and (4) chlorophyll indices, which do not saturate as readily as vegetation indices, were good predictors of yield, grain protein, and YLNS.;At the mixed grass prairie ecoregion site study findings were: (1) 130 kg N ha-1 applied at Haun 5-6 at had the greatest yield and protein response; (2) under non-limiting rainfall conditions, canopy reflectance collected at Haun 6 can be used for to predict yield, protein, and YLNS; (3) N applied in-season or pre-emergence had similar yield and grain protein; and (4) applying N fertilizer in-season at Haun 5-6 reduced economic risks and N induced lodging compared with pre-emergence N applications.;Economic analysis suggest that if the N fertilizer price was low,...