Herbicide residues in California agricultural soils

The question of herbicide residues, and possible effects on succeeding crops, is one of great importance to agriculture, particularly with increasing use of such chemicals to minimize hand labor requirements as well as soil compaction from weed cultivation equipment. This study, involving tests with 13 herbicides, used under typical field conditions at six locations in California, showed great differences in residual characteristics. At high rates (approaching four times the amounts normally used for weed control), simazine, bromacil, and trifluralin caused soil residue problems. Location of the tests also affected the amounts of residue for different herbicides.