Grain sorghum yield stability as affected by nitrogen fertilizer, tillage, and yield environment

As climate variability increases across the globe, understanding factors that affect grain sorghum (Sorghum bicolor L. Moench) yield stability is crucial. Limited information is available on the impact of soil management such as tillage and nitrogen rate interaction with weather on yield stability of grain sorghum. The objective of this study was to (1) evaluate the effects of tillage intensity (conventional tillage [CT], no-tillage [NT], and reduced tillage [RT]), nitrogen fertilizer rates, and year on grain sorghum yield and its stability and (2) identify the environmental drivers favoring specific sorghum management practices. This was done by analyzing a long-term study from 1975 to 2022 at Hays, KS, on wheat (W, Triticum aestivum L.)–sorghum (S)–fallow (F) rotation. Yield environments in this study refer to years that were grouped into four (9 or 10 years in each group), based on the average yield obtained in each of these years from this one experimental site. Results of the study indicated that Tillage × Year and N-rate × Year had significant effect on sorghum yields. The number of years (yield environments) that favored one tillage yielding greater than the others split almost equally, that is, 5–6 years for each of the three tillage. Application of fertilizer significantly increased grain sorghum yields in all years, except for four (1976, 1978, 2014, and 2015), compared to the control. Yield stability of grain sorghum evaluated across multiple years was affected by fertilizer rate but not by tillage. In very low-yielding (VLY) years, CT or RT had greater yields compared with NT. In low-yielding (LY) years, NT with >45 kg N ha⁻¹ yielded the greatest. In high-yielding years, tillage had no effect on sorghum yields but applying fertilizer-N increased grain yield. We concluded that an NT system with 45–90 kg N ha⁻¹ will most likely guarantee both high yield and stability across years (LY to very high yielding), except in VLY environment.