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United States Department of Agriculture

Agricultural Research Service

Title: Transport and Fate of Atrazine in Midwestern Riparian Buffer Strips

Authors
item Moorman, Thomas
item Reungsang, Alissara - IOWA STATE UNIVERSITY
item Ramesh, Kanwar - IOWA STATE UNIVERSITY

Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 31, 2000
Publication Date: N/A

Interpretive Summary: Atrazine is a herbicide with extensive use in the corn-growing regions of the U.S. Riparian buffer strips (RBS) are bands of trees and shrubs planted to intercept sediment in runoff in fields before it can enter streams. RBS may also reduce atrazine transport from agricultural land to streams. Herbicides entering RBS may be leached to the shallow groundwater beneath the RBS soil. We examined how atrazine was leached or degraded in soil from 5-year and 9-year old switchgrass buffer strips and compared atrazine behavior in RBS to that in adjacent cropped lands. All cropped and RBS soils were in the Bear Creek watershed located in central Iowa. Rapid atrazine leaching was observed in the 5-year and 9-year old RBS, but there was little difference in the physical mechanisms controlling leaching between the two RBS soils and the cropped soils. Atrazine retention was greater in RBS soils than cropped soils. Atrazine degraded more slowly in RBS soils than cropped soils. This difference was related to greater populations of atrazine-degrading microorganisms in the corn soil. This research suggests that some atrazine leaching is likely from RBS, but the RBS soils will be less vulnerable to leaching losses than cropped soils. This information helps to determine the impact of the Natural Resource Conservation Service streamside buffer program on pesticide losses from agricultural fields.

Technical Abstract: 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 the Bear Creek watershed located 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 were 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. This difference was related to greater populations of atrazine-degrading microorganisms in the corn soil.

Last Modified: 9/21/2014
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