Evaluating Water Uptake Functions under Simultaneous Salinity and Water Stress Conditions in Cherry Tomato(Solanum lycopersicum)

Various mathematical models are available for predicting the response of plants to combined water and salinity stress and their share in water uptake. The reduction functions are classified as additive, multiplicative, and conceptual models. In this study, 6 macroscopic reduction functions, namely, Van Genuchten (additive and multiplicative), Dirksen et al., Van Dam et al, Homaee and Skaggs were evaluated in a greenhouse experiment on cherry tomato, var. cherry tomato cluster. This experiment was performed based on a completely randomized design with 3 replicates and 2 levels of salinity (4 and 7 dSm-1). Water stress levels were imposed as matric potential decline during the study at 3 levels of available water depletion (40%, 50%, and 65%). The result of the study indicated that the crop response to water stress and salinity stress was incremental at 4 and 7 dSm-1 salinity levels. Among the multiplicative models, reduction functions of Dirksen model had better fit than others at 4 dSm-1 salinity level (RMSE=0.15 and ME=0.14).However, at 7 dSm-1, Van Dam (RMSE=0.017, ME=0.09) and Skaggs (RMSE=0.018, ME=0.14) had better fit to the measured data.