Calibration and assessment of evapotranspiration methods for cucumber plants in a Venlo‐type greenhouse

Abstract Accurate estimation of actual crop evapotranspiration (ET c ) is a necessary step in water resource management. Several ET c models have been developed and applied to estimate ET c in open fields. To date, there is no standard equation to estimate ET c under greenhouse conditions due to the structural and environmental differences between greenhouses and open fields. Therefore, an experiment was conducted in a Venlo‐type greenhouse in south‐east China during four planting seasons of cucumber plants in 2018 and 2019. Four methods, the pan evaporation method ( K p ‐method), crop coefficient model ( K c ‐method), Penman–Monteith model ( r c ‐method) and Priestley–Taylor model ( α PT ‐method), were employed and parameterized to estimate the ET c of cucumber in the Venlo‐type greenhouse. The performances of the four models were evaluated using ET c measured by lysimeters. The K p ‐method and α PT ‐method underestimated and overestimated ET c values with root mean square errors (RMSEs) equal to 0.79 and 0.49 mm day −1 for the spring‐summer planting season (SSPS) and 0.35 and 0.51 mm day −1 for the autumn‐winter planting season (AWPS), respectively. The K c ‐method and r c ‐method showed comparatively good performances in estimating cucumber ET c , with RMSEs equal to 0.53 and 0.34 mm day −1 for SSPS and 0.35 and 0.47 mm day −1 for AWPS, respectively.