Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 31, 2000
Publication Date: N/A
Atrazine is a herbicide with extensive use in the corn-growing regions of the U.S. Riparian buffer strips (RBS) have potential for reducing atrazine transport from agricultural land to streams in runoff. We compared transport and fate of atrazine in soil columns from 3-yr, 5-yr, and 9-yr old switchgrass (Panicum virgatum L.) buffer strips to atrazine behavior in adjacent lands cropped to corn or alfalfa pasture. All cropped and RBS soils were in Bear Creek in central Iowa. Intact soil columns were leached under saturated conditions with solution containing atrazine and bromide. Steady state breakthrough curves of atrazine and bromide were modeled with a mobile-immobile solute transport model. Preferential flow of bromide and atrazine was observed in the 5-yr and 9-yr old RBS, but there was little difference in transport characteristics between these two RBS soils and their adjacent cropped soils. Despite similar texture and organic C contents, atrazine sorption was greater in RBS soils than cropped soils, and total atrazine retention was greater in RBS soils. Atrazine degraded more slowly in RBS soils than cropped soils. The atrazine half-life in the 5-yr old switchgrass was 28 days, compared to 19 days in the soil cropped to corn. This difference was related to greater populations of atrazine-degrading microorganisms in the corn soil.