Controlled Drainage Effects on Crop Yield and Water Use Efficiency under Semi-Arid Condition of Iran

Control of water table is one of the management processes in irrigation and drainage networks to reduce nitrogen, other salts and drainage water. Suitable depth of water table is decided upon based on the balance between effective root depth, capillary zone and upward flow. In addition sensitivity to water logging, soil water storage capacity, and electrical conductivity of irrigation water and soil stratification should also be taken into account. if saline irrigation water is used, as a result of water loss through evaporation a salt stratification will result with the soil surface being more saline because of gradual accumulation of salts. The main effect of soluble salts on plants is osmosis effect because the presence of salts, adequate water absorption would be difficult for plants. This study was conducted to examine the feasibility of implementing water table control technique (i.e., controlled drainage) in an arid and semi-arid region (e.g., Iran) with particular attention to its salinity management. Two water table control treatments including: free drainage (FD) and controlled drainage (CD) with 40 cm controlled water table and three different irrigation water salinity namely: 0.75, 3.4 and 4.8 dS/m were considered. The experimental setup included 6 treatments and three replications. Treatments were applied in 18 lysimeters (90 cm height, 55 cm diameter). The crop cultivated in lysimeters was sorghum. The results indicated that CD method can be used in arid and semi arid regions. The evidence showed that yield of the CD treatment is 2.5 times higher than FD treatment.