Winter wheat yield stability as affected by fertilizer-N, tillage, and yield environment

With an increase in the frequency of hot-dry-windy weather and reported significant increase in winter wheat (Triticum aestivum L.) in-season average temperatures, it is important to understand how soil management affects yield stability. This study quantified the combined effects of tillage and fertilizer-N on winter wheat yield stability in a wheat–sorghum [Sorghum bicolor (L.) Moench]–fallow crop rotation. The research was conducted from 1975 to 2022 and the experimental design was a randomized complete block with a split-split-plot arrangement. Crop phases were the main plots, tillage (conventional tillage [CT], reduced tillage [RT], and no-tillage [NT]) in the sub-plot, and N application rates (0, 22, 45, and 67 kg N ha⁻¹ or 0, 45, 90, and 134 kg N ha⁻¹) in the sub-sub-plot. Results showed winter wheat yield under NT increased by 0.8 Mg ha⁻¹, compared with about 1.1 Mg ha⁻¹ for CT and RT, when environmental average increased by 1 Mg ha⁻¹ for N rates ≤90 kg ha⁻¹. Yields with CT and RT increased by 0.8 Mg ha⁻¹, compared with about 1.1 Mg ha⁻¹ rate for NT, when environmental average increased by 1 Mg ha⁻¹ for N >90 kg ha⁻¹. In 30%–52% of the time, CT wheat yield was greater than NT, but yield advantage with CT decreased as fertilizer-N rate increases. Yield stability of winter wheat varied by tillage and fertilizer rate. We concluded that NT wheat required greater N rates to reach the same yield potential as CT and RT, and long-term CT or RT wheat at 45 kg N ha⁻¹ was most stable.