CLIMATE-FRIENDLY LAWN MANAGEMENT PRACTICES: A CASE STUDY AT AN URBAN TURFGRASS IN NASHVILLE, TENNESSEE

This study was to understand the effects of lawn care practices on the global warming potential of urban lawns. Biogeochemical measurement and household survey were conducted at an urban turfgrass system at the Richland Creek Watershed in Nashville, TN. Using the survey data, we examined the long-term (i.e. 75 years) impacts of three lawn management archetypes with varying fertilization and irrigation intensity on soil organic carbon sequestration rate (dSOC), soil N₂O emissions, and net Global Warming Potentials (net GWPs). The model simulated N₂O emissions and net GWP from the three management intensity levels over 75 years ranged from 0.75 to 3.57 kg N ha^-1 yr^-1 and 697 to 2443 kg CO₂-eq ha^-1 yr^-1, respectively, which suggested that turfgrasses act as a net carbon emitter. Reduction of fertilization is most effective to mitigate the global warming potentials of turfgrasses. Compared to the baseline scenario, halving fertilization rate (1) and clipping recycle as an alternative to synthetic fertilizer (2) can reduce net GWPs by 17% and 12%, respectively. In addition, reducing irrigation and mowing are also effective in lowering net GWPs. The minimum-maintenance practice without irrigation and fertilization can reduce annual N₂O emissions and net GWPs by approximately 53% and 70%, respectively, with the price of gradual depletion of soil organic carbon, when compared to the intensive-maintenance practice. A lawn age-dependent best management practice is recommended: a high dose fertilizer input at the initial stage of lawn establishment to enhance SOC sequestration, followed by decreasing fertilization rate when the lawn ages to minimize N₂O emissions. A minimum-maintained practice with clipping recycle, and minimum irrigation and mowing, is recommended to mitigate global warming effects from urban turfgrass systems. Among all practices, clipping recycle may be a relatively malleable behavior and, therefore, a good target for interventions seeking to reduce the environmental impacts of lawn management through public education.