The herbicides metsulfuron-methyl, flupyrsulfuron-methyl, iodosulfuronmethyl and propoxycarbazone-sodium were incubated in a sandy loam soil at 15degreesC and at a soil water potential of -33kPa. The general order of persistence was propoxycarbazone-sodium > metsulfuron-methyl > flupyrsulfuron-methyl > iodosulfuron-methyl with first-order half-lives ranging from 10 to 89 days. The herbicides were also incorporated into soil at logarithmically increasing concentrations from 0.1 to 25.6 mug/kg. Sugar beet, oilseed rape, winter beans and spring barley were grown in the treated soils for 21 to 28 days. There were marked differences between compounds and between crops in the doses required to reduce shoot fresh weights by 10 (ED10) or 50% (ED50). In general, metsulfuron-methyl and flupyrsulfuron-methyl were more active than the other compounds tested. On the basis of the half-lives and crop response data, the herbicide degradation model PERSIST was used to predict safe recrop intervals following normal spring application of the study compounds.
