| The water use characters of cotton with drip-irrigation under film mulch were measured under the condition of sufficient and deficient water, and the crop coefficients (Kc) were determined for different growth stages. Based on the physical meaning of crop water stress index (CWSI), the function relationship between CWSI and crop actual evapotranspiration (ETa) was established. The ETa of cotton with drip-irrigation under film mulch could be calculated by the measurement value of ET0, Kc and CWSI of different stages. The relative error between calculated and measured ETa was less than 16% in single growth stage, and less than 4% for whole growth period. |