Influence of Nitrogen Source and Timing On Nitrate-N Leaching When Applied to Centipedegrass and St. Augustinegrass.

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 2008.  Over four growing seasons (2008-11), six nitrogen (N) sources were applied at 49.0 kg N ha^-1 every 60 days to both species.  Sources included: 1.) ammonium nitrate; 2.) urea; 3.) 30% Slow Release Nitrogen (SRN) 16-0-8; 4.) 50% SRN (19-0-19); 5.) Polymer Coated Urea (PCU) (41-0-0); and 7.) Organic biosolid (6-2-0).  For comparison purposes, a 98.0 kg N ha^-1 PCU treatment also was applied every 120 days to both species.  An untreated control was included.  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.  Soluble N sources yielded rapid improvements in green-up and turf quality following each application.  Throughout the study, centipedegrass exhibited better turf quality, color, and density than St. Augustinegrass.  Centipedegrass generally produced 8 – 10 times the quantity of shoots and ~30% more roots compared to St. Augustinegrass.  Nutrient import with the sod negated treatment differences in the inaugural year.  Over the 49 week study period (21 Apr 2009 – 30 Mar 2010), centipedegrass leached 67% less N than St. Augustinegrass (1.86 vs. 5.65 kg N ha^-1).  The winter of 2009/2010 was colder than normal resulting in significant deterioration of the St. Augustinegrass. The 49 week (20 Apr 2010 – 29 Mar 2011) leaching total was 23.16 kg N ha^-1 for St. Augustinegrass and 1.27 kg N ha^-1 for centipedegrass.