Evaluating the Effects of Agricultural Activities on Nitrate Contamination at the Kamfirooz District, Shiraz, Iran

To investigate the pollutants of the Kor River, water samples were collected during the rice-growing season in 2014. The first fertilizer was diammonium phosphate ((NH4)2HPO4). After first irrigation, supplemented with fertilizer usage, in the upper layers of soil causes an increase of NO3− concentrations to reach from 7.3 to 25.7 mgl-1 at the agricultural lands beside the Sarbast village. At this point, the NO3− concentration was 5.3 mgl-1. After the application of the third fertilizer (by using of urea fertilizer) flood irrigation, lead to decreasing of NO3− concentration at surface soil samples to 3.5 mgl-. At the same time, before first fertilizer application at the soils located beside of Doroodzan Lake the NO3− concentration was 17.9 mgl-1 but after the first fertilizing it increased up to 31.4 mgl-1. Therefore, the NO3− concentrations (31.4 mgl-1) exceeded from the acceptable limits for drinking water at this site. During the second and the third periods of urea fertilizer application, at this point the NO3− concentration decreased from 4.43 mgl-1 to 2.2 mgl-1. In spite of using high amounts of fertilizer because of flood irrigation, the NO3− concentrations leaches to surface groundwater. The maximum nitrate pollution occurs in June, when the rice plants are in the early stage of growth. As rice canopy coverage is increased, the nitrate concentration reduces. The result focuses on the vital roles of plant coverage in nitrate absorption. However if the fertilizer is rationally applied, phosphate loading into the river will be minimized. The rationality behind these procedures is explained.