ABSTRACT
Groundwater is a major human drinking water source and contributes substantially to surface water bodies when aquifers intersect the earth’s surface. High nitrate-nitrogen (NO3-N) concentrations in this water, whether from agricultural or non-agricultural sources, can create human health and environmental problems. Leaching of N fertilizer is a major agricultural factor contributing to high NO3-N concentrations in groundwater. Current cropping practices designed to achieve optimum grain yields can cause excess N to accumulate in the soil profile and become available for leaching. Oftentimes, there can still be a yield response to N fertilizer at rates that exceed the amount of N that plants can utilize. If this occurs, the economically optimum nitrogen level may result in NO3-N concentrations that exceed the maximum contaminant levels. Turf grasses and containerized horticultural crops often receive high rates of N fertilizer. Nitrogen management approaches that can be used to reduce the potential for NO3-N leaching include the following: reducing overall N fertilizer inputs; applying N in split applications, using slow-release N fertilizers; and growing cover crops to capture residual soil profile N before it can be leached to groundwater.
