Effect of Supplemental Irrigation at Different Irrigation Levels on Cotton Yield and Water Use Efficiency at Werer, Middle Awash, Ethiopia

Effects of supplemental irrigation at different irrigation levels on Cotton Yield and Water use efficiency conducted in Werer, Middle Awash, Ethiopia on 2018, 2019 and 2021 fiscal years. Cotton was planted in 18 experimental plots with irrigation treatment (No SI, 100% ETC, 80% ETC, 60% ETC, 40% ETC, and 20% ETC). Supplemental irrigation was conducted based on gravimetric soil moisture measurements. The results show more significant improvement in supplemental irrigation on water use efficiency at supplemental irrigation application rates than at full irrigation. Highest water use efficiency (WUE) (0.87 kg/m<sup>3</sup>) was achieved at rates of 80% ETc water requirement of crop. The lowest water use efficiency had recorded from application of 60% evapotranspiration requirement by supplemental irrigation. The highest cotton seed yield on average (3,252 kg/ha) was achieved from 80% application of supplementary irrigation to satisfy the water demand of cotton crop. The trend of water use efficiency increases as the application of supplemental irrigation decreases.