Assistant Professor, Department of Soil Science, Agriculture Faculty, Ramin University, Khuzestan

Practices of water table management to reduce the drainage volume and nitrate losses have caused to ensure the sustainability of irrigation and protection of associated ecosystems over the past decade. In this research, two water table management methods including free conventional subsurface drainage and controlled drainage was applied in the 63.41 ha field of the Imam Khomeini's Sugarcane Agro-industry, located in Khuzestan Province. Experimental treatments were a free drainage treatment (FD) and two controlled drainage treatments with water table controls set at 90 centimeter (CD90) and 70 centimeter (CD70) below the soil surface. Drainage outflow, nitrate nitrogen concentration, water table elevation and applied irrigation water amount were measured during study period. With the usage of controlled drainage, the total drain outflow from CD70 and CD90 area was decreased 62.48 and 48.98%, respectively compared with CD. The total of nitrate-nitrogen losses in drain outflow in CD70 and CD90 treatments was 58.43% and 47.25 %, respectively less compared with CD. The total applied water was decreased in CD70 and CD90 treatments 25.64 and 27.67 % compared with CD. The results of this study indicated that large-scale application of controlled drainage systems lead to significant reduction in drainage volumes and nitrate loads as well as increase the potential for economic and environmental benefits compared to unmanaged systems in arid and semi-arid regions of Iran.