Modeling Cotton Lint Yield and Water Use Efficiency Responses to Irrigation Scheduling Using Cotton2K

Decreasing groundwater supplies and increasing variability in weather challenge profitable cotton (Gossypium hirsutum L.) production in the Texas Rolling Plains. A modeling study was conducted using the Cotton2K model using weather data from 1980 to 2010 (31 yr) from the Texas Rolling Plains. Our objective was to study cotton yield, water use efficiency (WUE), and economic returns responses to irrigation, which included a combination of six evapotranspiration (ET) replacement levels (40, 60, 80, 100, 120, and 140% ET) and four irrigation durations (4, 6, 8, and 10 wk). The model was initially calibrated and validated using field data. Calibrated model was then used to run simulation scenarios. Maximum lint yield of 1838 kg ha(-1) was obtained by irrigating at 111% ET for 10 wk while maximum WUE of 2.65 kg ha(-1) mm(-1) was obtained by irrigating at 85% ET for 8 wk or 96% ET for 10 wk. This maximum lint yield required 530 mm of irrigation and 880 mm of total water. Maximum economic returns of US$1610 ha(-1) was obtained with 516 mm of irrigation water. However, if this amount of water is not available for irrigation, deficit irrigation at 85% ET for 8 wk is a good alternative strategy as it produced 1560 kg lint ha(-1) and $1240 ha(-1) economic returns with improved WUE. Our results indicate that scheduling irrigation by considering cotton ET demand could increase lint yield, WUE, and profit in the Texas Rolling Plains.