Changes in Soil and Plant due to Irrigation with Treated Domestic Wastewater and Its Effects on Alfalfa Yield

In order to investigate the effect of domestic wastewater and normal water (well water) on soil chemical properties and alfalfa yield, a research project was conducted for three years in Chahartakhteh Research Station. The experiment was performed in randomized complete blocks design including four treatments in three replications. Treatments were as follows: T1: Irrigation with normal water at farmers’ conventional amount; T₂: Irrigation with treated wastewater at farmers’ conventional amount; T₃: Irrigation with normal water to meet plant water requirement, T₄: Irrigation with treated wastewater to meet plant water requirement. The results showed that there were no heavy element in the soil and plants tested, but concentration of elements such as N, P, K, Na, and CI were increased in the plant, and also in 0-30 cm soil depth. However, electrical conductivity, available phosphorus, soluble sodium, magnesium and calcium increased in the treatments using wastewater. Also, in 30-60 cm soil depth, pH, electrical conductivity, total nitrogen and concentration of available iron, copper and sodium increased significantly (p <0.05). Crop yield increased through years of performing the study and results showed that alfalfa mean wet yield was 20367, 28992, 22138, and 29324 kg/ha for T1 to T4 treatments, respectively, while treatment no. 4 had the highest yield. Alfalfa wet yields in treatments irrigated with wastewater were higher than those using normal water (29158 and 21252.5 kg per ha, respectively). In general, results showed that use of effluent of treated domestic wastewater increased crop yield.