Assessment of yield and water use efficiency of drip-irrigated cotton (Gossypium hirsutum L.) as affected by deficit irrigation

Abstract

A field experiment was conducted for 2 consecutive years to evaluate the response of cotton crop to deficit irrigation under drip irrigation conditions. Water use efficiency (WUE), seed cotton yield, and fiber quality parameters were assessed at various irrigation levels. The experiment was set up to apply water at 4 different application rates: 50%, 65%, 80%, and 100% of the soil water depletion. These were abbreviated as DI50, DI65, DI80, and FI, respectively. The total amounts of irrigation water applied were 408 and 773 mm and the average seed cotton yields were 2909 and 5090 kg ha^{-1} for the DI50 and FI treatments, respectively. The highest seed cotton yield was obtained with full irrigation treatment in both years. Values of WUE were 0.65 and 0.70 kg m^{-3} for the FI and DI80 treatments, respectively, in the 2007 season. In the 2008 season, WUE values were 0.65 and 0.72 kg m^{-3} for the FI and DI80 treatments, respectively. The highest values of WUE and irrigation water use efficiency (IWUE) were observed in DI80 (0.71 and 0.75 kg m^{-3}, respectively), and the lowest IWUE in both years was seen with the FI treatment (0.66 kg m^{-3}). The yield response factor (ky) was 1.00 during the entire growing season, based on averages of the 2 years. No significant differences in fiber length, strength, uniformity, elongation, or fineness were observed between the FI and DI80 treatments in the 2008 season. The DI80 treatment showed significant benefits in terms of irrigation water savings and better WUE, indicating an attainable advantage of deficit irrigation employment under water shortage conditions.