|Reungsang, Alissara - IOWA STATE UNIVERSITY|
|Kanwar, Ramesh - IOWA STATE UNIVERSITY|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 22, 1998
Publication Date: N/A
Technical Abstract: Vegetative Buffer Strips (VBS) can reduce pesticide losses from agricultural areas by sediment trapping, infiltration, and sorption. This study was conducted to determine the degradation, adsorption, and desorption of atrazine in soils and thatch from seven year old grass hedge VBS of switchgrass (Panicum virgatum L.), eastern gamagrass (Tripsacum dactyloides), and big bluestem grass (Andropogon gerardi), established near Treynor, Iowa. Approximately 60, 20, and 3% of [**14 C-UL-ring]-atrazine was mineralized in soils collected from eastern gamagrass, switchgrass, and big bluestem grass VBS, respectively. Batch equilibrium techniques were used to measure the sorption partition coefficients. The l/n values for surface (0-15 cm) soils ranged between 0.83-0.85. The sorption partition coefficients (Kf) for surface soils from eastern gamagrass, switchgrass, and big bluestem grass were 1.72, 2.92, and 5.21, respectively. Cropped soils adjacent to eastern gamagrass, switchgrass, and big bluestem grass VBS had Kf values of 1.79, 2.54, and 5.81, respectively, which were not significantly different from VBS soils. Kf values for big bluestem (19.82) and switchgrass thatch (21.56) were significantly larger than respective soil Kf. The time to reach 90% of equilibrium in big bluestem thatch was 32 min and in switchgrass thatch was 57 min. In conclusion, atrazine sorption was significantly greater in thatch than in soil. Also, soils with higher mineralization rates had lower sorption partition coefficients, suggesting that sorption affects the bioavailability of atrazine in soils.