Soil Organic Carbon Input from Urban Turfgrasses

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 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 14-16% of SOC at 0-10 cm and 7-11% from 10-20 cm was derived from turfgrass. Irrigated-fine fescue added 1.40 ton C/ha/yr to the 0-20 cm soil profile, which is about 30% higher than the SOC input from non-irrigated fine fescue and irrigated-Kentucky bluegrass. Decomposition rates of SOC were 0.64 and 0.61 ton per hectare per year for irrigated fine fescue and Kentucky bluegrass, respectively, which were higher than under non-irrigated fine fescue and irrigated creeping bentgrass. Irrigation increased both net organic carbon input to the soil profile and SOC decomposition. Therefore the net carbon sequestration was similar for irrigated and non-irrigated fine fescue. All turfgrasses exhibited significant carbon sequestration (0.45 -0.78 ton ha-1). However, the net carbon sequestration rate is higher for fine fescue and creeping bentgrass than Kentucky bluegrass.