Deficit irrigation effects on yield and yield components of grain sorghum

Development of sustainable and efficient irrigation strategies is a priority for producers faced with water shortages. A promising management strategy for improving water use efficiency (WUE) is managed deficit irrigation (MDI), which attempts to optimize yield and WUE by synchronizing crop water use with the crop's reproductive stages. In comparison, deficit irrigation (DI) is applied at a fraction of the full (FI) irrigation requirement. Soil water use and grain yield of grain sorghum [Sorghum bicolor (L.) Moench] were evaluated in the High Plains of Texas, USA under three irrigation strategies: FI, DI, and MDI from 2010 to 2012. Grain yields of FI sorghum averaged 3.7 Mg ha−1 greater (p < 0.001) than DI sorghum in all years. However, MDI yields averaged 1.6 Mg ha−1 more than DI yields, which was significant in 2010 and 2012 (p ≤ 0.006). The WUE of FI sorghum was significantly greater than MDI in 2012 (p = 0.003) and DI in 2010 and 2012 (p ≤ 0.001) demonstrating that limiting water did not reduce WUE in two of the three years. Results suggest that WUE's of grain sorghum are not compromised under MDI compared with FI in most cropping seasons. While FI provides the greatest opportunity to reduce production risks through increased yield, if irrigation water is limiting, MDI provides less risk than DI due to its ability to maintain yield and WUE. Yield was stabilized in all years by increasing seed panicle−1 under MDI, which was supportive of concentrating irrigation water between growing point differentiation and half bloom to maintain ovules.