Abstract: Crop evapotranspiration(ETc),crop coefficient(Kc) and water use efficiency(WUE) are basic parameters for establishing irrigation schedule and regional water resources balance.They are changeable under different climate region and cultivation.The aim of this experiment is to understand the effect of plastic mulching on ETc,Kc and WUE of cotton in northern Shandong province.Based on field experiment,ETc was calculated by water balance equation,reference crop evapotranspiration(ETo) and Kc were calculated by using Penman-Monteith equation.The results indicated that the ETc and Kc of cotton in plastic mulching filed decreased by 101.5mm and 17.6% than CK(no mulch) respectively,and WUE increased by 29.3%.

Key words: Plastic mulching, Plastic mulching, Cotton, Crop evapotranspiration, Crop coefficient, Water use efficiency