In addition, crops should be planted within a day or two of the final tillage. Increasing the time between the final tillage and planting increases the head start weeds may have over the crop. Crops should be planted 3 to 5 days after burndown herbicides are applied for best results. Roundup and Gramoxone Extra applications can also be made after planting, but before the crop emerges to manage existing weeds. However, if rain occurs shortly after planting but before the herbicide is applied, the window for post plant treatment may be narrow for preventing crop injury.
Many growers use a combination of tillage and burndown herbicides to control early emerging weeds.
Tillage after applying a burndown herbicide, a common practice, can cause deeply buried or dormant seed to germinate. This can lead to increased weed pressure and decrease the effectiveness of the burndown herbicide. However, tilling fields in the fall or early spring can stimulate a large flush of weeds. This technique followed by a burndown herbicide treatment can be very effective at reducing the weed pressure in problematic fields. Managing early emerging weeds is extremely important to preventing crop yield loss and weed seed production.