Soil texture effect on nitrate leaching in soil percolates

Abstract

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 water by leaching, thereby becoming an environmental hazard. Soils have varied 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 reduce NO₃‐N contamination in the environment. A sand, 85:15 sand:peat Greensmix, a loamy sand, and sandy clay loam soils were placed in 2×3 inch 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 with water to collect 10 soil percolate samples of 50 mL each until a total volume of 500 mL was collected. Nitrate‐N was measured in each 50‐mL aliquot by automated colorimetry. The results showed that soil texture affected the retention of N03‐N in the sand, which adsorbed the least amount of NO₃‐N at 119 ppm, followed by the Greensmix at 125 ppm, loamy sand at 149 ppm, and sandy clay loam at 173 ppm. More NO₃‐N was released in the first 50 mL of the sand percolate at 63% followed by the 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 sand would be the poorest of soil types since NO₃‐N retention was low.