Document Type : Research Paper
Ph.D. Candidate, Department of Water Science, College of Agriculture and Natural Resources, Islamic Azad University, Science and Research Branch, Tehran, Iran
Associate Professor, Department of Water Science, College of Agriculture and Natural Resources, Islamic Azad University, Science and Research Branch, Tehran, Iran
Associate Professor, Islamic Azad University, Shahr-e-Qodss Branch, Tehran, Iran
The plant response of salinity and drought stresses and the role of them to reduce water absorption are expressed by several mathematical models. The reduction functions are classified additive, multiplicative and conceptual models. In this study six different macroscopic reduction functions, using data from greenhouse tomatoes, were evaluated: Van Genuchten (additive and multiplicative), Dirksen et al., Van Dam et al., Skaggs et al. and Homaee. The experiments were carried out on tomato plant in a factorial randomized complete block design with three replications. The treatments consist six levels of salinity (1, 2, 4, 6, 8 and 10 dS/m), and four levels of irrigation water (50%, 75%, 100% and 120% of crop requirement). The result indicated that in the absence of salinity stress all models were fit to the data measured, so, the results indicated that at low salinity levels, plant response to both water and salinity stress was additive and Van Genuchten additive model could simulated water uptake very well, while at higher salinity levels from 4 dS/m multiplicative models are a better fit. Among of multiplicative models, Skaggs et al. and Homaee models provided better fitness to measured data for tomato than other function, so as optimal absorption models are recommended.