|Jianmin, Xu - ZHEJIANG AG UNIV CHINA|
|Cheng, H - UNIVERSITY OF MINNESOTA|
Submitted to: China Environmental Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 1998
Publication Date: N/A
Interpretive Summary: The greatest potential for ground water contamination is in areas that have sandy soils, which are used for agricultural crop production such as irrigated potato production. A two-year potato field study was conducted to determine the dissipation and movement of the herbicide metribuzin in a sandy loam soil in north central Minnesota. We found that metribuzin degraded rapidly in the surface soil during the first two weeks after application, then degraded much more slowly. By the end of the growing season less than 3 percent of applied chemical remained in the top 6 inches of soil. We could find no chemical in the soil between 6 and 24 inch depth during the growing season. We found however, very small amounts of metribuzin in water samples at a depth of 4 feet. These data indicate that very small amounts of applied metribuzin can move with water through this soil. However, these data also show that the threat of groundwater contamination is not as great as the public believes. Farmers can use this information to show that responsible use of agricultural crop protection chemicals can have minimal impact on ground water quality.
Technical Abstract: Two-year potato field studies were conducted to determine the dissipation and movement of metribuzin in a sandy loam soil. Metribuzin was found to dissipate rapidly during the initial 7 to 15 days in 0 to 15 cm layer soil, then decrease slowly with time. The residue levels at the end of the growing season were 5.9 and 2.3 ug/kg in 1993 and 1994 respectively. Metribuzin was detected in only 5 among 379 soil samples taken from 15 to 75 cm in two years. Sixty-six percentage of field water samples at 135 cm depth contained detectable levels of metribuzin in 1994. The detectable concentration of metribuzin in water samples ranged from 0.06 to 15.85 ug/kg, and the medial concentration was 1.94 ug/kg. The dissipation of metribuzin in fields was much faster than its degradation under laboratory conditions.