Continuous no-tillage winter wheat response to nitrogen fertilizer by yield environment

Maintaining crop residue through no-tillage (NT) has allowed increased water storage and continuous cropping in dryland wheat (Triticum aestivum L.)-based systems. However, there is little information regarding nitrogen (N) fertilizer rates for a continuous NT wheat cropping system across various yield environments. The main objective of this study was to determine agronomic optimum N rates for a continuous NT wheat in different yield environments. The study was conducted from 1981 through 2003 at the Kansas State University Agricultural Research Center near Hays, with six N fertilizer rate treatments (0, 22, 45, 67, 90, and 112 kg N ha-1). Experimental years were divided into four yield environments: very low yielding (VLY), low yielding (LY), high yielding (HY), and very high yielding (VHY). Results showed that LY environments required a relatively greater N amount (79-98 kg N ha-1) than HY to VHY environments (72-73 kg N ha-1) to attain optimal yields. The optimal yields at low-yield environments were smaller (1184-1654 kg ha-1) than in high-yield environments (2181-2733 kg ha-1). Protein yield increased by 120 g for 1 kg increase in grain yield. We concluded that the optimum N fertilizer rates for continuous NT wheat ranged from 70 to 100 kg N ha-1, but these rates should be adjusted based on yield environments. Optimal N rate was greater in low-yield (79-98 kg N ha-1) than high-yield (72-73 kg N ha-1) environments.Yields at optimal N rate for low-yield (1184-1654 kg ha-1) were less than high-yield (2181-2733 kg ha-1) environments.Protein yield increased by 120 g for 1 kg increase in grain yield.No-tillage N rates should be adjusted based on yield environments.