where, ETais the total evapotranspiration (mm) during the experi-mental period; I is the amount of irrigation (mm); P is the effectiveprecipitation (mm); S is the difference in soil moisture betweenthe end and beginning of the experiment; R is the surface runoff loss(in this study, surface drip irrigation was used, there was no surfacewater accumulation, so R could be ignored); D is the drainage loss(in this study, irrigation system was controlled by a water meter,and the irrigation amount was low, so there was no drainage).