Nitrogen source and timing impact on nitrate leaching from turf

The leaching of nitrogen (N) from sports fields is an inefficient use of nutrients and potentially harmful to the environment. Several field studies were conducted to determine what effect N source and timing of application had on NO3 leaching from Kentucky bluegrass (Poa pratensis L.). Sites were located on sandy soils, two on coastal southeastern NY and one site in central NY. Nitrogen sources vary from very water soluble (urea) to slow release (coated urea, biosolid and urea-formaldehydes). Ion exchange resin was placed (300 mm deep) below the root zone to estimate the extent of NO3 leaching. Two application-timing studies were conducted, a single late fall application (9.8 g N m(-2)) or 2-4 non-late fall applications (19.7 g N m(-2) y(-1)). During a dry and normal precipitation year, N leaching for water-soluble sources ranged from 0.9-5% of the amount applied, whereas as slow release sources had 0.5-7.4% leaching. During a year with 291 mm of rainfall more than normal, water-soluble sources had N leaching values 12 to 29% of the amount applied where slow release sources had much less leaching (2 to 7%). Applying N at the end of the growing season resulted in NO3 leaching in sandy coastal areas, ranging from 29-47% of the amount applied with urea while slow release sources were much lower (0-12% of the amount applied). In the colder inland site, late fall applied N was much less likely to leach (5% for urea). Sports field managers can reduce N leaching by carefully applying N in the late fall and by using slow release sources.