investigation on nitrogen leaching to soil depth by irrigation with wastewater

because of water shortage in arid and semi-arid regions, reuse of wastewater and treated effluents for agricultural irrigation has become an essential matter now. while these kinds of water contain a lot of nutrients such as nitrogen, by using them we could be able to increase the soil fertility and decrease both the chemical nutrient consumption and the costs of agricultural production. however, due to high potential of pollutant and transferability of nitrate components (no3) through soil, careless application could cause ground and surface water contamination. with this regard, in order to investigate the transformation of nitrogen below the root zone as a result of irrigation with wastewater, a series of lysimeter studies were carried out in tehran area. a statistical “factorial experiments in the form of randomized complete design” (3x3x3) was used. raw and treated domestic wastewater of ekbatan housing complex and well water (control) have been applied for irrigation of raw edible vegetables such as parsley, carrot and tomato for two years. the results showed that nitrogen leaching through soil to drain depth, were between 12.93% to 33.75% of entranced amount for irrigation with raw wastewater and 23.30% to 38.17% for treated wastewater. also, mass balance analyses indexed by nitrogen showed a mean efficient reduction of 96.6% to 98.9%. maximum no3 concentration during two years was about 12 mg/lit, which happened in drainage water of lysimeters that irrigated with raw wastewater. this amount of no3 was very lower than the permissible no3 amounting of iranian standards (50 mg/lit) for discharge the effluents to surface water resources.