Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 1995
Publication Date: N/A
Interpretive Summary: The movement of herbicide residues in soils of northern climates during the winter and early spring is not well known. The objective of the research was to determine movement of alachlor and metolachlor, two herbicides often found in ground water of various states, during winter and early spring months in Minnesota and South Dakota soils. Results indicate that herbicide remaining in the soil in the fall may undergo some redistribution during winter freezing and thawing cycles of the soil, but will remain in the surface soil. However, substantial downward movement can occur in the spring with water from snowmelt or spring rains.
Technical Abstract: The movement of herbicide residues during winter and early spring in frozen and thawing soils of northern climates is not well documented. Continuous water films near soil particles in frozen soils, water infiltration during snow melt and thaw, or spring rains may redistribute herbicide residues in the soil. This study empirically assessed alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] movement in soils during winter and early spring. Alachlor and metolachlor were applied to frozen soils in late November or early December at Rosemount, MN and Aurora and Beresford, SD. Soils were sampled in February, March, and April or May and dissected incrementally to 105-cm. Herbicides moved from the surface into the soil at each site. Herbicide redistribution was greatest at the last sampling date when alachlor was measured to 105 cm. Metolachlor was less mobile than alachlor with most remaining at or above the 15-cm depth. These data indicate that herbicides may leach into the soil during the spring with water supplied by snowmelt, the melting frost lens, or spring rains.