Effect of Combined Salinity and Drought Stress on Economy of Soilless Culture of Greenhouse Tomato

In order to investigate the economics of simultaneous effect of salinity and drought stress on growth and yield of tomato plant (LycopersiconesculentumMill. Cv. Oriental), four levels of irrigation (125% ET, 100%ET, 75%ET and 50%ET) and six levels of salinity (0.1, 1.3, 3, 5, 7, and 9 dS/m) were combined in a factorial and completely randomized design with 3 replication in a greenhouse soilless culture. Economic model of deficit irrigation optimization was extracted and used for growing tomato in a greenhouse under salinity and drought stresses. The results of this model showed that the net profit of full irrigation of tomato in soilless culture in greenhouse using water of 0.1, 1.3, and 3 dS/m was equal to the net profit of deficit irrigation at 36%, 21%, and 24%, respectively. Thus, considering the large number of tomato greenhouses with soilless production and very high price of chemical fertilizers and other costs related to plant nutrition and irrigation, applying approximately 25% deficit irrigation will cause a corresponding reduction in total costs of production, which is economically significant.