Evaluating nitrate leaching between diverse turfgrass sites

One probable source of nitrate contamination in residential areas is fertilization of turfgrass. We investigated nitrate leaching below eight maintained turfgrass sites in a coastal plain outwash setting under natural field conditions by collecting monthly samples of soil water from suction lysimeters and analyzing for nitrate as nitrogen (NO₃-N) concentrations. The sites varied in fertilizer practices and soil and turfgrass properties. In 2003 average NO₃-N concentration for the sites treated with organic fertilizer was 4.71 ppm and the average for sites treated with chemical fertilizer was 2.92 ppm. This indicates organic fertilizer leaches more nitrate yet the opposite was true for 2004 (6.89 ppm for chemical fertilized sites and 3.49 ppm for organic fertilized sites), emphasizing the need for multiple year studies. We created a leaching index, calculated as infiltration rate multiplied by soil organic matter, to better compare nitrate leaching between sites in the natural environment. Predicted nitrate concentrations at one meter increases as leaching index increases. We evaluated depth profiles at four of the eight sites and found that nitrate concentrations are not conservative from 60 to 150 cm.