Nitrous Oxide Emissions and Nitrate Leaching From Synthetic and Alternative Turfgrass Management Programs.

Municipalities are increasingly restricting lawn fertilizers and in some cases prohibiting synthetic fertilizers while allowing organic or natural fertilizers. The objectives of our study were to

investigate and compare the turf quality, contribution to NO₃^- leaching, and N₂O emissions of five turfgrass management programs.  Turfgrass swards composed of either of a seed mixture of Poa pratensis L., Lolium perenne L., and Festuca rubra L. spp. rubra or a transplanted mature P. pratensis sod were established during August of 2010, in Madison, WI on a silt loam soil in a randomized complete block design with four replications.  Treatments consisted of a control with no inputs, a program utilizing a synthetic fertilizer and a liquid formulation of 2,4-D, triclopyr, and fluroxypyr, a synthetic fertilizer with a granular formulation of 2,4-D, MCPP, and dicamba, a program utilizing a combination of synthetic and organic fertilizer with mesotrione herbicide, and an organic poultry fertilizer and an FeHEDTA herbicide treatment.  Herbicides were applied when weed abundance exceeded 5 percent.  Nitrous oxide measurements were collected weekly and also after fertilization using a photoacoustic gas-analyzer and a vented non-static collection chamber.  Root zone leachate was collected from a depth of 36 cm with low-tension wick lysimeters.  Turf quality and color were assessed visually (1-9 scale) each month; Normalized Difference Vegetation Index was measured every other week.  Turf and weed cover were assessed each May, July, and September.  The levels of N₂O measurements fluctuated enormously (94 – 1300 µg N₂O-N m^-2 h^-1) and the highest levels were observed directly following fertilization.  Nitrate concentrations varied from 0.0 – 33 mg NO₃^--N L^-1 with no significant treatment differences.  Turf color and quality were greater for plots that received fertilizer than the control. Preliminary results suggest synthetic and organic fertilizer applications provide equal quality turf and have similar potential for nitrogen loss.