Study of evapotranspiration and crop coefficients for eggplant in a Venlo‐type greenhouse in South China

Abstract

AbstractDetermination of greenhouse evapotranspiration (ETc) and the response mechanism of environmental factors are important for accurate irrigation management and greenhouse environmental control. Models for predicting ETc under greenhouse conditions are extremely scarce in comparison to those under open field conditions. Meteorological data inside and outside a Venlo‐type greenhouse were measured from April to July 2015 to estimate the reference evapotranspiration (ET0) based on four approaches (the Penman–Monteith model, a revised Penman–Monteith model, a modified Priestley–Taylor approach and the Irmark–Allen fitting approach). The daily ET0 values inside the greenhouse calculated from these four methods presented similar variation trends but were somewhat different. The ETc for eggplant in the greenhouse was measured by lysimeters to estimate the crop coefficient with the FAO‐56 method (Kc = ETc/ET0), and the response mechanism of environmental factors on the ETc was analysed. The results showed that the crop coefficients of the eggplant were different, with values of 0.94–1.97, 0.83–1.87, 0.64–1.34 and 0.58–1.21 based on the ET0 from the Penman–Monteith model, revised Penman–Monteith model, modified Priestley–Taylor approach and Irmark–Allen fitting approach, respectively; the net radiation showed the highest correlation with the ETc; the secondary parameters were the air temperature and solar radiation, with R2 values equal to 0.77 and 0.75, respectively; and the relative humidity and soil temperature showed different extents of influence on the ETc. The results of this study provide more options for greenhouse cultivars to accurately determine the ETc of eggplants using the FAO‐56 method based on the availability of different meteorological data.