Nitrate in Surface and Subsurface Flow from a Small Agricultural Watershed

Abstract

Abstract A small agricultural watershed on Cowarts loamy sand in the Georgia Coastal Plains was planted in corn ( Zea mays L.) each year from 1969 to 1971. Surface and subsurface water samples were collected during each natural rainfall runoff event and NO 3 ‐N was determined. The initial weighted average NO 3 ‐N concentration was 5 ppm in the subsurface runoff for 3 months before the first planting. The average was 7 ppm in 1969, 10 ppm in 1970, and 9 ppm in 1971. The concentration of NO 3 ‐N in most of the surface runoff for 3 years was less than 1 ppm; the maximum was 3 ppm. Subsurface flow accounted for 80% of the total runoff during the study period. Thus, greater amounts of NO 3 ‐N were discharged in subsurface flow than in surface flow from this watershed.