Validation of dual-crop coefficient method for calculation of rice evapotranspiration under drying–wetting cycle condition

Based on data collected from rice fields under drying–wetting cycle condition, the procedure of dual-crop coefficient (Kcd) approaches was calibrated and validated to reveal its feasibility and improve its performance in rice evapotranspiration (ETc) estimation. It was found that Kcd based on FAO-recommended basal crop coefficients (Kcb) underestimated dual-crop coefficients in monsoon climate region in East China. The recommended coefficient (Kcp) value of 1.2 was not high enough to reflect the pulse increase of rice ETc after soil wetting. The Kcb values were calibrated as 1.52 and 0.63 in midseason and late season, and the Kcp value was adjusted as 1.29 after soil wetting in rice field under drying–wetting cycle condition. The dual-crop coefficient curves based on locally calibrated KcbCal and KcpCor matched well with the measured crop coefficients and performed well in calculating rice evapotranspiration from paddy fields under drying–wetting cycle condition. So it can be concluded that the procedure of dual-crop coefficient method is feasible in rice ETc estimation, and locally calibrated Kcb and Kcp can improve its performance remarkably.