Modelling transpiration of soilless greenhouse cucumber and its relationship with leaf temperature in a mediterranean climate

Three experiments (spring and autumn-winter seasons) with soilless cucumber crop (cv. Phenomeno) were conducted in order: (i) to calibrate the simplified Penman - Monteith model equation as affected by greenhouse microclimate (ii) to validate the prediction efficiency of the model at different climatic conditions and (iii) to establish a relationship between transpiration and leaf temperature. To determine Penman-Monteith model parameter variables related to the plants such as transpiration and leaf area index (LAI), so as environmental variables (i.e., radiation, temperature, humidity) were recorded. The results revealed that the determined model parameters were suitable for the whole cucumber cultivation cycle and a wide range of climatic conditions. However, parameterization of the model using autumn-winter crop data revealed superiority compared to spring data, as indicated by the correlation coefficients. Model validation showed a good fit between simulates and measures allowing implementation in commercial soilless practices. With respect to greenhouse microclimate, cooling affected daily mean air temperature and vapor pressure deficit, so as model coefficients. Leaf temperature indicated a good correlation with transpiration and the prediction equation was validated under different greenhouse climatic conditions. These results may be of value in Mediterranean greenhouses, enabling a more efficient water resource management without significant losses in agricultural productivity.