Clay and organic matter absorb herbicides, making them less available to kill weeds. Soils with high clay and organic matter require greater herbicide rates. Sandy soils with low organic matter require lower rates to avoid site injury. A general classification for herbicides that are able to move away from the site of absorption to other parts of the plant. Two or more pesticides combined in a single application.
Temperature greatly influences herbicide effectiveness.
Best range 65 - 85 degrees F. Low temperatures may result in reduced weed control whereas high temperatures may cause site injury. The capacity of a substance to produce injury.