Weed control in zone/ no-tillage corn is more difficult than in reduced or conventionally tilled and planted fields for two reasons. First, some weed control options are eliminated in zone/ no-tillage cropping systems. Second, some weeds are more aggressive and/or more difficult to control in zone/ no-tillage situations. Effective control programs require proper identification of the existing and potential weed problems and knowledge of herbicides available. Chemical weed control in zone/ no-tillage corn may involve the following:
- Control of existing vegetation with a burndown herbicide application before or at the time of planting may be needed. Herbicides used for this purpose include *Gramoxone SL 2.0 or the various formulations of glyphosate including Roundup products, Durango DMA, Touchdown Total, etc. If burndown applications are made in combination with residual (preemergence) herbicides, they eliminate competition from existing vegetation long enough to get the corn established and to allow for rainfall activation of the residual herbicides. If residual herbicides are not used, burndown treatments provide a window for total postemergence weed control programs to be applied. With herbicide-resistant corn, like glyphosate-resistant (Roundup Ready) or Liberty Link hybrids, burndown and residual herbicides may be applied early postemergence in one-pass.
- If residual herbicides are not applied with the burndown application, weed control in zone/no- tillage corn may require preemergence or early postemergence herbicide applications to control weeds that emerge after planting. In addition, postemergence herbicides may be required to control escaped weeds such as dandelion.
Zone/no-tillage burndown guidelines are given in Table 3.7.4. Refer to Table 3.7.3 for preemergence or total postemergence weed management guidelines for field corn.