Persistence and Movement of CDAA and CDEC in Soil and the Tolerance of Corn Seedlings to These Herbicides

NE of the major characteristics limiting the usefulness of herbicide applications concerns the persistence of chemical activity in the soil. In many instances, the herbicides break down too quickly to obtain satisfactory weed control. On the other hand, there is the possible hazard that a chemical may be too persistent and thus endanger the growth of succeeding crops. Another closely related factor is susceptibility to leaching. It is especially important when chemicals are used that are toxic to the crop plants as well as the weeds. In 1954, two new compounds were introduced for use as preemergence herbicides in crops (7, 8). These herbicides were 9-chloroN,N-diallylacetamide (CDAA) and 2-chloroallyl diethyldithiocarbamate (CDEC). Preliminary data indicated that both of these compounds were more specific for annual grass weeds than for broadleaf weeds. The object of this study was to learn more about the persistence and movement of CDAA and CDEC when applied to the soil. Since corn would be a major crop on which CDAA and CDEC might be used, laboratory tests were conducted to learn the actual tolerance of corn seedlings to these pre-emergence herbicides in soil.