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

Abstract

Accurate estimation of actual crop evapotranspiration (ETc) is a necessary step in water resource management. Several ETc models have been developed and applied to estimate ETc in open fields. To date, there is no standard equation to estimate ETc 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 (Kp‐method), crop coefficient model (Kc‐method), Penman–Monteith model (rc‐method) and Priestley–Taylor model (αPT‐method), were employed and parameterized to estimate the ETc of cucumber in the Venlo‐type greenhouse. The performances of the four models were evaluated using ETc measured by lysimeters. The Kp‐method and αPT‐method underestimated and overestimated ETc 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 Kc‐method and rc‐method showed comparatively good performances in estimating cucumber ETc, 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.