Comparison of Evapotranspiration Partitioning and Dual Crop Coefficients of Direct-Seeded and Transplanted Rice in the Poyang Lake Basin, China

Abstract

Direct-seeded rice (DSR) has received much attention because of its advantages in having low labor costs compared to the traditional transplanted rice (TPR). Investigating the differences in evapotranspiration (ET) partitioning and crop coefficients (Kc) between DSR and TPR is essential in understanding how agricultural water demand is affected by crop rotation. In this study, the water fluxes of two-year (2017–2018) growing seasons were collected from a pair of eddy covariance (EC) towers for DSR and TPR in the Poyang Lake Basin, Southern China. This study aims to compare the seasonal characteristics of the ET components (evaporation, E, and transpiration, T) and dual crop coefficients (basal crop coefficient, Ks·Kcb, and soil/water crop coefficient, Ke) of DSR with those of TPR. The ET values for the 2017 and 2018 growing seasons were 374 mm and 436 mm for the DSR, respectively, and 309 mm and 342 mm for the TPR. The seasonal T/ET values in 2017 and 2018 were 0.40 and 0.46 for the DSR, respectively, and 0.49 and 0.52 for the TPR, indicating that the higher ET values for the DSR can be mostly attributed to E. The DSR had overall higher Kc values than the TPR because of free water evaporation during the initial stage and a higher plant density. Our results enrich the Kc dataset for DSR and have great implications for the sustainable irrigation of the Poyang Lake Basin in the future.