Assessing atrazine persistence in soil following a severe drought

Atrazine in soil is degraded more rapidly under conditions of adequate soil moisture and relatively warm temperature. A 1988 drought in Michigan created a need to assess atrazine levels in soil to advise producers on crop management options. Results reveal that on a statewide basis, atrazine levels remaining in soil were not unusually high in late fall, despite the severe summer drought. The greatest correlation with atrazine persistence was observed with soil cation exchange capacity. Both the immunoassay and Soxhlet-gas chromatography techniques provided adequate estimates of atrazine residue levels in soils for making decisions on rotational crop selection.