NITRATE MOVEMENT IN A CHILEAN AGRICULTURAL AREA IRRIGATED WITH UNTREATED SEWAGE WATER

Nitrate concentrations in soils and drainage and well waters were determined in a 15-ha field representing about 4,000 ha of agricultural land irrigated exclusively with raw sewage water for >25 years. Analyses of the percolating water below the root zone indicated that the leached NO3-N was about 350 kg/ha per year. The transit time for water to move through the unsaturated zone to the saturated zone at a depth of 2 to 2.2 m was < 1 year, and the leaching fraction was estimated as 0.63. Concentrations of NO3-N ranged from 20 to 35 mg/liter in the percolating water of the unsaturated zone, whereas two well waters contained 9 and 14 mg/liter.; Nitrate concentrations in soils and drainage and well waters were determined in a 15-ha field representing about 4,000 ha of agricultural land irrigated exclusively with raw sewage water for more than 25 years. Analyses of the percolating water below the root zone indicated that the leached NO//3** minus -N was about 350 kg/ha per year. The transit time for water to move through the unsaturated zone to the saturated zone at a depth of 2 to 2. 2 m was less than 1 year, and the leaching fraction was estimated as 0. 63. Concentrations of NO//3** minus -N ranged from 20 to 35 mg/liter in the percolating water of the unsaturated zone, whereas two well waters contained 9 and 14 mg/liter.