Wednesday, November 7, 2007 - 1:25 PM
269-2
Nitrogen Losses from Cool-season Turfgrasses.
A. Martin Petrovic, Cornell University, Dept of Hort, 134A Plant Sci. Bldg., Ithaca, NY 14853
The public concern about the fate of nitrogen (N) applied to turfgrass has culminated in proposed legislation to ban or limit the kind, amount and timing of turfgrass nitrogen fertilization in some parts of the US. Over the past 30 years there had been a wealth of research published on the fate of N in the turfgrass system that now allows a more complete picture on important management options available to minimize the risk of N contamination of surface and groundwater. A review of the recent cool-season turfgrass literature reveals several factors important in reducing the risk of N leaching losses including : age of the site (reflected in organic matter content), fall fertilization timing and long term view of the source of N. The impact of age of the site on NO3 leaching was conducted in 12 year study in MI. In the early years, NO3 concentration was usually below 1 mg/L, while apparently peaking at over 40 mg/L in year 12 at a higher rate of N application. A lower N rate resulted in peak leachate NO3 concentrations in year 11 at 10 mg/L. In a CT study, the extent of NO3 leaching increased as the application of N was made later in the year (Sept. to Dec.). Results from a NY study found when averaged over a wide range of rainfall conditions (below, at and above normal yearly precipitation) the source of N applied, that had a wide range in N release rate, had no effect on the extent of NO3 leaching. Older studies have showed the need to control summer irrigation to reduce the amount of N leaching. Thus, to reduce the risk of N impacts to groundwater, N applications should be less as the site matures at determined by soil organic matter analysis, limit the amount N applied in mid to late fall and to control the amount of irrigation to closely match the amount of evapotranspiration.