SOIL TEXTURE EFFECT ON NITRATE LEACHING IN SOIL PERCOLATES

Nitrate nitrogen (NO3-N), which is an essential source of nitrogen (N) for plant growth, is now also considered a potential pollutant by the Environmental Protection Agency (EPA). This is because excess applied amounts of NO3-N can move into streams by run-off and into ground wat er by leaching, thereby becoming an environmental hazard. Soils have v aried retentive properties depending on their texture, organic matter content, and cation exchange capacity (CEC). The purpose of this study was to determine the effect of soil texture on NO3-N retention to red uce NO3-N contamination in the environment. A sand, 85:15 sand:peat Gr eensmix, a loamy sand, and sandy clay loam soils were placed in 2x3 in ch metal cylinders and soaked in a 240 ppm solution of NO3-N for seven days to saturate the soil with NO3 ions. The columns were leached wit h water to collect 10 soil percolate samples of 50 mL each until a tot al volume of 500 mL was collected. Nitrate-N was measured in each 50-m L aliquot by automated colorimetry. The results showed that soil textu re affected the retention of NO3-N in the sand, which adsorbed the lea st amount of NO3-N at 119 ppm, followed by the Greensmix at 125 ppm, l oamy sand at 149 ppm, and sandy clay loam at 173 ppm. More NO3-N was r eleased in the first 50 mL of the sand percolate at 63% followed by th e Greensmix, loamy sand, and sandy clay loam at 58, 46, and 37% NO3-N released, respectively. Soils with more silt, clay, and organic matter retained more NO3-N than the straight sand. Therefore, a straight san d would be the poorest of soil types since NO3-N retention was low.