Crop evapotranspiration (ET_C) of rice under an alternate wetting and drying (AWD) irrigation practice may be different from conventional (CON) irrigation methods due to the drying (water stress) phase. The focus of this study was to identify a suitable approach for estimating ET_C for a rice crop under AWD practice. Field lysimeters were used for estimating daily ET_C under AWD and CON practices during monsoon and non‐monsoon seasons. Lysimeter‐based evapotranspiration (ET_{C_Lys}) was compared with that resulting from the product of reference evapotranspiration (FAO‐56 Penman–Monteith equation), crop coefficient (FAO tabulated values‐K_{C_Tab} and FAO equation‐K_{C_Eqn}) and soil water stress coefficient (linear equation‐K_{S_Lin}; FAO equation‐K_{S_FAO}; logarithmic equation‐K_{S_Log}). The K_{C_Eqn} and K_{S_FAO} methods were found to be better estimates for K_C and K_S, respectively, for AWD practice. The mean K_C in initial, mid and late season for AWD were found to be very close to CON practice. The K_S was observed to vary from 1 to 0.15 for AWD. Overall, AWD irrigation practice saved 10–20% irrigation water with about 2% reduction in grain yield and 13% reduction in ET_C. The reduction in ET_C indicated that K_S must be considered when calculating the ET_C in rice under AWD irrigation practice.

中文翻译：

---

交替湿润和干燥灌溉实践下水稻的蒸散量估算*

由于干燥（水分胁迫）阶段，交替湿润和干燥（AWD）灌溉实践下的水稻作物蒸散量（ET _C）可能与常规（CON）灌溉方法不同。这项研究的重点是确定一种在AWD做法下估算水稻作物ET _C的合适方法。字段渗漏测定计被用于日常估计ET _Ç在季风和非季风季节AWD和CON做法之下。将基于蒸渗仪的蒸散量（ET _{C_Lys}）与参考蒸散量（FAO‐56 Penman–Monteith方程），作物系数（FAO列表值‐ K _{C_Tab）的乘积进行比较}和FAO方程‐ K _{C_Eqn}）和土壤水分胁迫系数（线性方程‐ K _{S_Lin} ; FAO方程‐ K _{S_FAO} ;对数方程‐ K _{S_Log}）。该ķ _{C_Eqn}和ķ _{S_FAO}发现方法成为更好的估计ķ _Ç和ķ_小号，分别为AWD实践。发现AWD在开始，中期和后期的平均K _C非常接近CON实践。该ķ_小号观察到AWD从1变化到0.15。总体而言，AWD灌溉实践节省了10–20％的灌溉水，谷物产量降低了约2％，ET _C降低了13％。ET _C的减少表明，在AWD灌溉方式下计算水稻的ET _C时必须考虑K _S。