Lysimeter Study of Water Table Management Impact on Nitrates and Phosphates Leaching and Drainage Water Salinity in Dezful

Todays water table management (WTM) plays an important role in saving water and nutrients such as nitrate and phosphorous and also in improving downstream water quality. However, the use of WTM in hot and dry areas such as Khuzestan may be restricted due to high evapotranspiration and capillary flow. In this study, using plastic lysimeters, the feasibility of using water table control methods (controlled drainage and subsurface irrigation) accom`plished with leaching management was investigated in Dezful climate under Tomato cultivar of Kingstone cultivar. For this purpose, three treatments including free drainage, controlled drainage and subirrigation, each in three replications were considered in lysimeters with 90 cm in heghit and 40 cm in diameter. In this study, the shallow groundwater with salinity of 2.3 dS/m was kept at a depth of 50 cm from the soil surface in the controlled drainage and subirrigation treatments. The results showed that the percentage of salts mass in drainage water of free drainage and controlled dariange treatments were 65 and 45%, respectively. The percentage of NO3-N and phosphate mass loss in free drainage treatment were 20.9 and 8.1%, respectively that were higher than those in controlled drainage treatment with values of 13.7% and 5.7%. Since, the electrical conductivity in the root zone in subirrigation treatment did not reach to 3 dS/m, additional leaching did not performed in this treatment. Therefore, the results of this study promise the effectiveness of WTM at 50 cm from the soil surface at laboratory scale and in warm and semi-arid areas.