Deep Nitrate Movement in the Unsaturated Zone of a Simulated Urban Lawn

Abstract

Abstract The increasing incidence of NO 3 contamination in municipal wells is a growing concern in the Midwest. While leachates from N fertilizers applied to agricultural lands can impact the water quality in municipal wells, there is also the potential for leachates from turfgrass fertilizers to be groundwater contaminants. In this study, five plots were treated with ammonium nitrate (34‐0‐0,N‐P‐K) at rates of 0, 1.0, 1.5, 2.0, and 2.4 kg N/100 m 2 and irrigated‐ The turf received approximately 640 mm of water during the 34‐d study. Analysis of soil water from 15, 6‐m continuous cores showed that as much as 95% of the NO 3 applied in late August leached below the turfgrass root zone. Average NO 3 concentrations in the pulse ranged from 34 to 70 mg/L NO 3 ‐N. Thirty‐four days after fertilization the center of the pulse was at ≈1.2 m with the leading edge at 2 to 2.5 m. This vertical rate of movement is similar to that predicted by the one‐dimensional CMLS model. The relatively high uniform NO 3 concentrations in the unfertilized plot indicated that with excessive irrigation the water alone supplies NO 3 in excess of the turfgrass need.