Impact of Fertilizer Applications to Semi-Dormant and Dormant Lawn Grasses On Environmental Quality.

Centipedegrass (Eremochloa ophiuroides [Munro] Hack) and St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze.) were established as sod at the University of Florida, West Florida REC in 2006.  Over three (2006-09) winter seasons (Sep – Mar), urea nitrogen (N) was applied every 45d to plots at rates of 0, 6.1, 12.3, 24.5, and 49.0 kg N ha^-1.  Each plot contained a lysimeter with a surface area of 0.22 m².  Leachate collection was conducted weekly.  Data collection included total NO_-3-N leached and turf quality, color, and density.  The initial sampling (2006) yielded greater quantities of NO_-3-N leaching than subsequent leaching cycles which was likely due to the N that was applied during the production of the sod prior to installation on the research site.  At no time during 2007-08 did NO_-3-N leach to any significant level regardless of turf species or rate of applied N.  The average leaching during the five cycles ranged from 0.2 –5.0% of applied N. At times, N leaching from untreated plots exceeded that from N-treated plots.  In 2008-09, negligible quantities of NO_-3-N leached from either turf species during the first two fertilizer cycles.  During the third, fourth, and fifth cycles, however, the 49.0 kg ha^-1 N rate had increased levels of NO_-3-N in the leachate.  This equates to 5.8% of the applied N when looking at the final fertilizer cycle.  No differences in NO_-3-N leaching occurred between centipedegrass and St. Augustinegrass in 2008-09.