Defining management strategies to maximize net soil carbon and nitrogen retention in turfgrass systems

Quincy D Law, Purdue University

Abstract

Soil carbon (C) sequestration has been proposed as a method to reduce atmospheric carbon dioxide (CO2). Managed turf areas are both a source and a sink for greenhouse gases (GHGs) including CO 2, methane (CH4), and nitrous oxide (N2O), among others. Management practices, including turfgrass selection and mowing, influence the amount of C and N stored in the soil, as well as the direct and indirect GHG emissions. Thus, the objective of this research was to determine how turfgrass selection (both species and cultivar) and mowing practices (such as frequency and grass clipping management) influence the annual mowing requirements and dry matter yield, soil C and N accumulation, and GHG flux (CO2, N2, and CH4) in a turfgrass system. Planting slower growing turfgrasses resulted in fewer annual mowing events: Kentucky bluegrass (Poa pratensis L.) required fewer annual mowing events than tall fescue (Schedonorus arundinaceus Schreb.), and slow-growing cultivars needed to be mown less than the moderate-growing cultivars, which were mown fewer times than the fast-growing cultivars. Mowing by the one-third rule and collecting grass clippings also reduced mowing requirements. However, the faster growing species (i.e. tall fescue) and cultivars had higher annual dry matter yields, and returning grass clippings also increased yield. The same practices that increased dry matter yield, except for growth rate, also increased labile and total soil C concentrations. Furthermore, returning grass clippings increased leaf tissue N concentration as well as total soil N concentration. Tall fescue had a greater CO2 flux than Kentucky bluegrass, and returning grass clippings had a greater CO2 flux than collecting clippings, which occurred on five and one of the six collection dates, respectively. Nitrous oxide flux differed for growth rate on one collection date, though it was likely due to a fertilizer response. There was not a measurable CH4 flux. The results of this study highlight the importance of turfgrass selection and mowing practices on the C and N dynamics and biogeochemical cycling in a turfgrass system. All turfgrasses and management practices resulted in a system-wide net C sink, though the magnitude of the sink varied by management strategy.

Degree

M.S.

Advisors

Patton, Purdue University.

Subject Area

Agronomy|Horticulture|Plant sciences|Soil sciences

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