This study was based on the premise that the most logical approach to reducing nitrate leaching in soils was to limit the amount of nitrate in the soil solution at any one time. Methods of limiting the concentration of nitrate in the soil solution while maintaining an adequate supply of available nitrogen for plant growth are reported. Timing of nitrogen application was found to be a very effective means of reducing nitrate leaching. When nitrogen was applied in the fall as much as 3-fold more nitrate was found to have leached below 60 cm in the soil by June as compared to applications made in March. A nitrification inhibitor, N-Serve, was found to be very effective in reducing the amount of nitrate leached. Slow release sulfur-coated ureas and treatment of nitrogen fertilizers with N-Serve were found to be effective means of reducing leaching losses of nitrate when fertilizers were applied in the fall or winter. Losses of 0.5 and 3.6% of nitrogen applied as fertilizer occurred in runoff water when normal rates of nitrogen were applied to a grassland watershed. Lysimeter studies indicated that from 0.04% to 6% of the applied fertilizer nitrogen could be leached below 120 cm in a silt loam soil depending on the source of nitrogen.

Chiefly tables. Includes appendices. Issued August 1977. Prepared by Texas A&M University, Texas Agricultural Experiment Station, College Station, Tex., under project S-800193. Includes bibliographical references (pages 111-112).