ARS | Publication request: Soil Organic Carbon Input from Urban Turfgrasses

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 17, 2009
Publication Date: N/A

Interpretive Summary: Urban grassland covers over 16 million ha in the U.S., and it is ubiquitous in the American urban landscape. Estimates are that among the total US land devoted to urban development, 39-54% is covered by turfgrass. Despite the large acreage of turf, the role of turf in balancing the nation’s C budget has largely been unexplored. Carbon sequestration ability is intricately linked to the cycling of soil nutrients including nitrogen, phosphorous, potassium, and other micronutrients and clipping management. In this study, different carbon sequestration rates were observed under different treatments. Carbon sequestration rates were 0.74, and 0.78 ton per hectare per year for irrigated-fine fescue and creeping bentgrass, respectively, which are higher than that of non-irrigated fine fescue and irrigated Kentucky bluegrass. We also observed that irrigation increased both gross SOC input to the soil profile and SOC decomposition in fine fescue. Thus, soil organic C accumulation rate is associated with both turfgrass rooting depth and irrigation availability. In summary, our experiment demonstrates that measuring carbon isotopic composition appears to be an appropriate approach to study SOC dynamics and that soil carbon sequestration and organic carbon decomposition rates are different for different turfgrasses and different management regimes.

Technical Abstract: Turfgrass is a major vegetation type in the urban and suburban environment. Management practices such as species selection, irrigation, and mowing may affect carbon input and storage in these systems. Research was conducted to determine the rate of soil organic carbon (SOC) changes, soil carbon sequestration, and SOC decomposition of fine fescue (rain fed and irrigated), Kentucky bluegrass (irrigated), and creeping bentgrass (irrigated) using carbon isotope techniques. Aboveground tissues were collected for biomass determination and C isotope ratio analysis. Soil was sampled for determination of root mass, soil bulk density, SOC, soil organic nitrogen, and C isotope ratio. Our results indicated that four years after establishment, about 17-24% of SOC at 0-10 cm and 1-13% from 10-20 cm was derived from turfgrass. Irrigated-fine fescue added 3.35 ton C ha-1 yr-1 to the 0-20 cm soil profile, which is about 141% higher than the SOC input from non-irrigated fine fescue, and 55% higher than irrigated-Kentucky bluegrass and creeping bentgrass. The soil organic carbon decomposition rates was 2.61 ton C ha-1 yr-1 for the irrigated fine fescue at 0-20 cm soil profile, which was 2-fold higher than SOC decomposion for non-irrigated fine fescue and about 50 - 74% higher than that for Kentucky bluegrass and creeping bentgrass. Irrigation increased both net organic carbon input to the soil profile and SOC decomposition. We found that all turfgrasses exhibited significant carbon sequestration (0.32 -0.78 ton ha-1 yr-1) during the first 4 years after turf establishment. However, the net carbon sequestration rate is higher for fine fescue and creeping bentgrass than Kentucky bluegrass.