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TURFGRASS SCIENCE

Soil Organic Matter Changes in Turfgrass Systems Affect Binding and Biodegradation of Simazine

^a Crop Science Dep., North Carolina State Univ., 100 Derieux Place, Raleigh, NC 27695
^b Soil Science Dep., North Carolina State Univ., 100 Derieux Place, Raleigh, NC 27695. Funded by the Center for Turfgrass Environmental Research and Education at North Carolina State University

^* Corresponding author (adam.hixson{at}basf.com).

Concern about pesticide losses from maintained turfgrass areas led us to examine the fate of the triazine herbicide simazine in turfgrass systems and, specifically, interactions between simazine binding to soil organic matter and biodegradation. Soil samples were removed from turfgrass systems of different ages, placed in microcosms, conditioned as sterile or nonsterile, and exposed to ¹⁴C-simazine. At seven sampling intervals, the soil was extracted and ¹⁴C was separated into three pools; bound, extractable, and CO₂. With sterilized surface soil (0–5 cm), 52, 70, and 71% of applied ¹⁴C-simazine was bound to soil from the 4-, 21-, and 99-yr-old turfgrass systems, respectively, after 16 wk. With nonsterile conditions, biodegradation became dominant, as 60 to 80% of the ¹⁴C was recovered in the CO₂ fraction and binding was held at 20%. Among all soils evaluated, bound ¹⁴C and ¹⁴CO₂ production was lower in subsurface soil (5–15 cm) from the 4- and 21-yr-old turfgrass systems. ¹⁴C-simazine disappearance time (DT₅₀) values under nonsterile conditions ranged from 0.9 to 5.8 wk. Results indicate that turfgrass systems have a relatively low amount of simazine available for leaching as the systems age due to a large capacity for biodegradation and binding to organic matter.

Abbreviations: DT₅₀, 50% disappearance time • LSC, liquid scintillation counting • OM, organic matter • SMBC, soil microbial biomass carbon • TLC, thin layer chromatography