The herbicides studied were diallate, dicamba, dichlobenil, dinitramine, simazine, triallate, trifluralin and 2,4-D. Diallate, dicamba and 2,4-D degrade over a single growing season while residues of all other herbicides were detected. There is little degradation over the winter and breakdown resumes in May. Triallate and trifluralin may build up from one growing season to the next and care must be taken to avoid excessive buildup and the possibility of crop damage.