Impact of Deficit Irrigation on Soil Salinity and Cucumber Yield under Greenhouse Condition in an Arid Environment

Continuing agricultural expansion and urban development in Saudi Arabia, (located in an arid climate), together with an increased demands for more water supplies, calls for more efficient irrigation practices, and an increase in Crop Water Productivity (CWP). Throughout the present study, a deficit irrigation system was investigated for its impact on soil salinity, crop response factor (Ky), CWP, and a crop, namely cucumber’s (Cucumis sativus L.) yield. Cucumber seeds were planted in a greenhouse equipped with drip irrigation system. The crop evapotranspiration (ETc) was assessed through Pan Evaporation method (PE) and estimation based upon Penman-Monteith equation (PM). The results revealed good agreement between PE and PM ETc. The irrigation treatments consisted of four levels of ETc (40, 60, 80, and 100% of ETc) in addition to the traditional one as practiced by local farmers. At the 60 and 80% ETc treatments, the deficit irrigation was tested at different growth stages (Initial, developmental, middle, and late stages of crop growth). Each of the treatments was carried out in three replicates. The results showed that soil salinity in general increased with decreasing level of applied water. The crop cucumber could tolerate shortage of water during the middle season growth stage, when the Ky values ranged between 0.57 and 0.76. The level of water used up in 100% ETc treatment was much lower than that in the traditional drip irrigation as practiced by farmers. In other words, the CWP values increased with water consumption being decreased. The results also indicated that the highest values for CWP were found for the most stressed treatment of 40% ETc, while on the other hand the overall crop productivity had decreased.