Total N and Nitrate-N Concentrations Through the Soil Profile as Affected by Soil Management Practices.
Byron Belvitt, Robert Taylor, and James Shuford. Alabama A&M Univ, 4900 Meridian Street, Normal, AL 35762
Nitrogen fertilizer applied to agricultural soils for improving crop productivity is of environmental concern for the general public mainly because of the potential risk of groundwater contamination. The distribution of total Nitrogen (N) and nitrate-N in soils may be influenced by soil management practices including no-till, conventional tillage, crop rotation, and organic amendment applied to soils. This study was conducted on a Decatur silty clay loam soil (clayey, kaolinitic, thermic, Rhodic Paleudult) at the Alabama A&M University Agricultural Research Station, Hazel Green, AL, to (i) determine total N and nitrate-N concentrations as affected by organic amendment (poultry litter), tillage and cropping systems; and (ii) identify strategies to minimize the potential adverse effects of N in the environment. Soil samples were collected at varying depths (0-30, 30-60, 60-90, and 90-120 cm) following corn-soybean and soybean-corn rotations and analyzed for total N and nitrate-N concentrations. Results showed that total N concentration in the soil was significantly (P < 0.05) affected by tillage and nitrogen source. Plots treated with organic amendment had the highest N concentration (0.36 g/kg). Nitrate-N concentration under corn-soybean rotation was significantly reduced by 10.40 mg/kg and increased under soybean-corn rotation by 5.85 mg/kg. Furthermore, the data suggest that the use of no-tillage with corn-soybean rotation may reduce nitrate-N concentration beyond the crop root zone.