Document Type

Thesis - University Access Only

Award Date

1998

Degree Name

Master of Science (MS)

Department / School

Agronomy

Abstract

In many Great Plains states, soil loss by wind (wind erosion) removes as much or more more soil from agricultural land than water erosion. Wind-eroded soil particles may act as a transport mechanism by which agrichemicals are moved from their site of application to off-site areas. Samples of wind-eroded sediments deposited in road ditches during the winters of 1994, 1995, and 1996 in eastern South Dakota and western Minnesota were collected and analyzed for atrazine (2-chloro-4-ethylamino-6 isopropylamino-1, 3, 5- triazine), atrazine metabolites, deethylatrazine (2-chloro-4-ethylamino-6-amino s-triazine) (DEA) and deisopropylatrazine (2-chloro-4-amino-6-isopropylamino-striazine) (DIA), and alachlor (2-chloro-2', 6'-diethyl-N(methoxymethyl) acetanilide), and total nitrogen. Atrazine or atrazine metabolites were detected in 100, 73, and 96% of the samples taken in 1994, 1995, and 1996, respectively, with overall concentrations ranging from 0.3 to 147.0 ng g-1. Alachlor was detected in 40, 27, and 33% of the samples with an overall concentration range of 3.0 to 59.6 ng g-1. Total nitrogen was detected in every sample taken and concentrations ranged from 3. 3 to 80. 7 μg g-1. Movement of these agrichemicals 4-10 months after application to offsite areas indicates a need for better soil management that keeps these chemicals in their zone of application. A field study was conducted to determine atrazine, alachlor, and acetochlor (2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide) concentrations on various wind-erodible (<1.0 mm) and nonwind-erodible (>1.0 mm) size fractions from a Barnes loam (fine-loamy, mixed, Udic Haploboroll) and a Brandt silty clay loam (fine silty, Pachic Udic Haploboroll) using treatments of incorporation and nonincorporation after herbicide application. Soil was removed 1, 7, and 21 days after application and separated into 6 sizes with midpoint values ranging from 0.05 to 1.68 mm and herbicide concentrations were determined using HPLC techniques. Dissipation rates and ability to suppress weeds were also determined for these herbicides. Incorporation of the herbicides immediately following application reduced chemical concentrations on wind and nonwind-erodible size fractions up to 4 and 6x, respectively. Dissipation rates were fastest for sediments initially having higher herbicide concentrations following application, generally the sediments from the nonincorporation treatment. Weed suppression was generally excellent both years for tank mixtures of atrazine + alachlor and atrazine + acetochlor for a wide range of weeds. A batch study was conducted to determine atrazine sorption and desorption characteristics as influenced by sediment size. Ring labeled [14 C] atrazine solutions (6.5, 1 3.0, 19.6, and 39.2 μmole L-1 in 0.01 M CaC12) were added to 6 size fractions (wind and nonwind-erodible) of a Barnes loam and Brandt silty clay loam. Sorption and desorption isotherms were determined using the Freundlich equation after 2 4 h and 5 additional 24 h periods, respectively. Atrazine was sorbed least to the smallest size (0.05 mm) and greatest to the largest size (2.3 4 mm) in each soil. Desorption isotherms indicated hysteresis. Results of the sorption-desorption laboratory experiment indicate that atrazine transported by wind-eroded sediments may contribute to off-site pollution, but effects may be prolonged. A low affinity of wind-erodible sediments for herbicide sorption will greatly increase the potential of off-site contamination. Results of this field study indicate that a substantial amount of chemicals can be transported by wind-eroded sediment, and that incorporation following application can reduce surface transport by 8 0% and still maintain excellent weed control. A laboratory study showed that atrazine contained on wind-eroded sediment can desorb and therefore contribute to surface and groundwater pollution.

Library of Congress Subject Headings

Agricultural chemicals -- Environmental aspects Wind erosion Soil erosion

Format

application/pdf

Number of Pages

106

Publisher

South Dakota State University

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