The present extensive use of herbicides in soil application has resulted in a great deal of interest in the breakdown of these chemicals in soil (1, 4, 6, 8). An increasing demand exists for information that will permit fairly accurate predictions of the residual life of these chemicals (4). The breakdown of chemicals in soil has been repeatedly shown to be the result of microbiological activity in part but other factors are also known to contribute to the disappearance (1, 4, 5, 7, 8, 9).