Effect of Irrigation with Low Quality Water on the Efficiency of Agricultural Gypsum in Sodic Soils

Columns experiment was constructed on the farm of Agriculture College, Al-Azhar University to study the efficiency of agricultural gypsum in improving the chemical properties of alkaline clay soils (El -Salam Canal project soil) which irrigated with agricultural drainage water. Soil samples were taken from the research region; they were prepared then mixed with agricultural gypsum GR. The treatments were watering with varying quality having different values of SAR. The experiment consisted of 15 columns comprised five treatments in three replicates completely randomized design. Plastic columns with the diameter of 15 cm and 45 cm length and tatted with a slot at the bottom so that drained water are collected regularly during the probationary period for the purpose to track the change in some chemical properties such as EC and pH. The results showed an increase in the values of pH, EC in treatments that contain high concentration of sodium used for irrigation, which led to a decrease in the efficiency of agricultural gypsum through the soil column of experiment compared to the control. The results also showed a linear relationship between SAR and ESP. The obtained linear equation was ESP = 1.0148 SAR+ 6.0165 where R2 = 0.831. It was also found that, by increasing the SAR values in irrigation water, the efficiency of agricultural gypsum decreased. Therefore, it could be recommended adjusting the amount of added agricultural gypsum to soils irrigated with water with high contents of sodium to prevent sodium accumulation in root zone.