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ARS Home » Research » Publications at this Location » Publication #116090
Title: CLIMATE AND SOIL MOISTURE EFFECTS ON HERBICIDE CONCENTRATIONS IN RUNOFF FROM AGRICULTURAL WATERSHEDS

Author
item TOWNSLEY, S - UNIV OF CALIFORNIA, DAVIS
item WALLENDER, W - UNIV OF CALIFORNIA, DAVIS
item Shipitalo, Martin

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Although high concentrations of surface-applied chemicals have been noted in the first runoff event, a literature search reveals no attempt to correlate soil moisture or climatic data to concentration level. Therefore, our objective was to identify significant factors in agricultural runoff and to establish meaningful parameters for landscape scale runoff modeling efforts. Data from the Coshocton Experimental Watershed are being analyze to find correlation(s) between various climate and soil moisture measurements, tillage practices, and timing between herbicide application and runoff producing events. Four small watersheds, under corn and soybean rotation were instrumented as part of a soil and nutrient loss experiment. In addition, chisel tillage practices were compared with no-till, and four commonly used herbicides (alachlor, atrazine, linuron, and metribuzin) were rotated annually. The data set has event-based runoff analysis coupled with 4 years of hourly weather and soil moisture data. Although the average annual losses were small (<0.5%), the yearly losses vary widely with rainfall timing and amount. Runoff and concentration amounts were higher from no-till watersheds than chiseled watersheds. Significant relationships between ln(concentration) and ln(days after application) are noted in this data set and in other reports in the literature, but this data set only accounted for 78 to 88% of the variability. A preliminary examination of the data indicate that as the time between herbicide application and a runoff-producing event increases, the less significant the relationship. Therefore, a more detailed study of individual factors such as soil moisture may lead to greater understanding of other significant factors influencing concentrations in agricultural runoff.