Sorption of herbicides in relation to soil variability and landscape position

Using, the soil-water sorption partitioning coefficient (Kd), this study qu antified the spatial variation of 2,4-D sorption by soil in an undulating-t o-hummocky terrain landscape near Minnedosa, MB, Canada. Herbicide sorption was most strongly related to soil organic matter content and slope positio n, with greatest sorption occurring in lower landscape positions with great er soil organic matter content. The relation between sorption and slope pos ition was more pronounced under conventional tillage (CT) than under long-t erm zero-tillage (ZT). Using multivariate regression and three independent variables (soil organic matter content, soil clay content and soil pH), the prediction of herbicide sorption by soil was very good for CT (R-2 = 0.89) and adequately for ZT (R-2 = 0.53).