No matter what kind of soybean variety or corn hybrid you plant this season, your fields could greatly benefit from a pre-emergence herbicide with a residual. I always recommend growers put a residual product down, especially in front of soybeans. Residual herbicides help control tough weeds before they get too large and tough to eliminate. And with mid- to high fertilizer prices, why would you want to use available fertilizer to feed weeds in your fields? Fortunately, the last few springs have been relatively wet, and the weeds didn’t have to compete for moisture in our fields. If this weather pattern changes, however, and we get an extremely dry spring, there’s a large chance these weeds will compete even more for available moisture and fertilizer.
With just a little amount of rainfall, pre-emergence herbicides with residual reactivate to provide longer lasting control over a number of broadleaves and grasses, including waterhemp, lambsquarter, ragweed, kochia, palmer amaranth and velvetleaf. Combined with a residual, pre-emergence herbicides manage weeds as they germinate or newly emerge, which is the most vulnerable time for weeds.
The earlier you can kill or stunt the growth of weeds, the less chance they have to over populate and challenge the crop for growing room and resources. It also makes it easier and more cost-effective when it comes time for a post-emergence applications, as the crops are allowed to canopy and shade out the remaining weeds. This may allow growers to make fewer applications or even eliminate the need for a post-emergence application depending on the success of the pre-emerge and residual.
For soybeans, I recommend applying full rates of pre-emerge herbicides 20 to 30 days before planting. Don’t start cutting rates, which gives the weeds a better chance of becoming resistant.
In corn, I recommend applying up to seven days before planting or before corn emerges to help kill and suppress the weeds from the very beginning. Then you can apply a post-emergence application — and probably less of it — to tackle any weeds that survived and have fully emerged.
There are a handful of pre-emergence herbicides available for both corn and soybeans, so make sure you do your research and read the labels before you get started.