Reducing Nitrogen Fertilization Rate in Spring Wheat–Pea Rotation Sustains Spring Wheat Yield and Quality

The reduced N fertilization rate and N supplied by pea (Pisum sativum L.) residue may sustain subsequent spring wheat (Triticum aestivum L.) growth, yield, and quality. We examined the response of spring wheat growth, yield, and quality to cropping systems and N fertilization rates from 2012 to 2019 in the US northern Great Plains. Cropping systems were conventional till spring wheat–fallow (CTWF), no-till spring wheat–fallow (NTWF), no-till spring wheat–pea (NTWP), and no-till continuous wheat (NTCW), and N fertilization rates to spring wheat were 0, 50, 100, and 150 kg N ha−1. Wheat plant density and straw yield were 13–100% greater for CTWF and NTWF than NTWP and NTCW in most years. Wheat grain yield and protein concentration were also 15–115% greater for CTWF and NTWF than other cropping systems at most N fertilization rates and years. In contrast, wheat grain test weight was 1–2% lower for CTWF and NTWF at most N fertilization rates and years. Increasing N fertilization rate mostly increased grain yield and protein concentration but reduced grain test weight for most cropping systems and years. Although CTWF and NTWF with or without N fertilization increased wheat yield and quality, these practices are not sustainable due to reduced annualized yield, soil health, and environmental quality. Because of similar or greater grain yields and test weights among NTWP with 50 kg N ha−1 and NTWP and NTCW with other N rates, NTWP with reduced N rates may sustain spring wheat yield and grain size but not grain protein in the northern Great Plains.