Analyzing Evapotranspiration Components and Crop Coefficients for Catch Crop Field with Small Area at Different Plant Densities in a Greenhouse

We cultivated dent corn as a catch crop for controlling soil salt conditions in field plots at different densities, namely, 7.3 (low), 59.7 (normal) and 119.5 (high) plants m−2 in a greenhouse, where environmental elements and plant growth were measured for analyses of evapotranspiration components relating to the catch crop effects. Using the Penman-Monteith model with specific parameters incorporated for the crop and greenhouse, leaf transpiration and soil evaporation were estimated. Further crop coefficients were analyzed by dividing actual evapotranspiration by a reference evapotranspiration determined from meteorological data. Leaf area index for the normal and high density treatments reached 14 and 22, respectively, which were extremely high values compared to those for various other crops. Transpiration and its ratio to evapotranspiration increased with plant growth and density. Crop coefficients also increased with leaf area index and transpiration, and the coefficients for the normal and high density treatments reached high values of 1.5–2 and 2–3, respectively. These findings reveal characteristic features of plant growth and water dynamics in a catch crop field. The results of this study will contribute to the optimization of catch crop cultivation and to elucidate the crop's effects on soil salt conditions in greenhouses.