Effects of crop management on the fate of three herbicides in soil

The effects of the management of straw, nitrogen fertilization, and application rates on the dissipation of metsulfuron-methyl, methabenzthiazuron, and trifluralin were investigated in a 3-year field crop rotation study, complemented with laboratory studies. The dehydrogenase activity in soil was measured as an indicator of the soil microflora. The effects were specific for the herbicides investigated. The amendment of straw accelerated the dissipation of trifluralin and methabenzthiazuron. Furthermore, the movement of trifluralin, but not methabenzthiazuron, in the top 30 cm of the soil was reduced. Nitrogen fertilization and high application rates significantly decreased only the dissipation of methabenzthiazuron in the laboratory. Dehydrogenase activity in soil was influenced mainly by the amendment of straw. There was no evidence for cumulative effects on herbicide dissipation due to crop management within the crop rotation.