Soil-to-Atmosphere Greenhouse Gas Emissions From High- and Low-Input Turf Systems of Central Kentucky.

Lawns cover 20 million ha in the US, at least three times more area than other irrigated crops.   Lawns can require significant water and energy resources and under some conditions, may contribute negatively to regional eutrophication and air pollution issues. However, they can also sequester carbon and nitrogen into soil pools, thereby potentially mitigating increasing atmospheric greenhouse gas concentrations. This project quantified how turf species and management regimes influence soil CO₂ and N₂O emissions from lawns in the transitional climatic zone of the eastern US.

Three replicate plots of tall fescue [Schedonorus arundinaceus (Schreb.)], Kentucky bluegrass [Poa pratensis (L.)], and an endemic multi-species stand were established in the spring of 2012 in Lexington, KY.  These lawn types were managed as either high-(tall fescue, Kentucky bluegrass) or low-maintenance (endemic multi-species) systems. High maintenance plots received regular pesticide and fertility treatments applied by a local lawn company. Fescue and bluegrass plots were irrigated to replace 0.60 and 0.80 of ET, respectively.  The low maintenance plots received none of these treatments.  All plots were mowed as needed.  CO₂ and N₂O efflux measurements were taken from February 2013 until October 2013 using a photoacoustic spectroscopy gas analyzer.

There were no significant differences in trace gas fluxes between high maintenance stands, or between high- and low-maintenance stands.  Rates of CO₂ and N₂O ranged from 411-763 mgCm^-2h^-1 and 45-619 mgNm^-2h^-1, respectively, over the growing season.  Three spring and summer applications of nitrogen (1/4lb 1000ft^-2) did not stimulate any additional emissions.  However, the fall nitrogen application (2lb 1000ft^-2) did stimulate significant trace gas emissions from the high maintenance plots.  These results suggest that the environmental impacts of these three turf systems, from a trace gas perspective, are relatively similar in central Kentucky.  However, large fall nitrogen applications in high-maintenance systems can be significant contributors to greenhouse gasses.