Pesticide Mobility in Soils III. Influence of Soil Properties
1971
Helling, Charles S.
Soil parameters influencing pesticide movement were isolated using simple correlation and multiple linear regression analyses. Mobilities of 12 pesticides on 14 soils were first characterized by soil thin-layer chromatography. Mobility of nonionic compounds was inversely related to adsorption of similar compounds, field moisture capacity, organic matter and clay contents, and cation-exchange capacity. Mobility of acidic compounds (dicamba, picloram, fenac, and 2,4-D) was directly correlated with soil pH and inversely with picloram adsorption. Pesticide mobility tended to be directly related to increased water flux. When soils were grouped according to their clay mineralogy, there was a tendency for movement of acidic pesticides to be directly related to montmorillonitic clay content and inversely related to nonmontmorillonitic clay content. Regression equations usually contained field moisture capacity, water flux, and often simazine or chlorpropham adsorption terms for predicting movement. These parameters are highly correlated with soil organic-matter content, which does not itself appear in the regression equations. The average deviation of predicted from observed mobility, across all soils and pesticides, was 0.04 RF units.
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