Growing non-GMO soybeans: What do you need to know?
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Even with the substantial number of Roundup Ready soybean acres in the state this year there are several producers that will be growing non-GMO soybeans. Since some of these producers haven’t planted non-Roundup Ready soybeans for several years, there are few pointers that should be remembered for effective weed control in conventional (non-GMO) soybeans.
1) It is important to start clean! As with all weed control strategies, starting with a weed-free seedbed is essential. This can either be done with tillage or an effective preplant burndown herbicide treatment. In no-till soybeans using an effective burndown treatment is particularly important since typical postemergence soybean herbicides will not adequately control typical no-till weeds. For adequate control of several of these no-till weeds, 2,4-D, glyphosate, or a combination of the two should be used in the burndown treatment. When including 2,4-D ester in the burndown treatment this application should be made at least 7 days prior to soybean planting.
2) Producers of non-GMO soybeans should also consider using a preplant or preemergence herbicide with residual activity as a foundation program for hard to control weeds such as common lambsquarters, common ragweed, giant ragweed and eastern black nightshade. Relying on a total POST program for control of these weeds can be difficult. Control of these weeds has also been difficult in Roundup Ready soybeans programs so it is important to control these species with a two-pass herbicide program. By waiting to control these weed with a total POST program many times these weeds can become too large, may be affected by the environment (hardened off by hot-day weather) or may just not be effectively controlled. Getting a start on controlling these weeds early in the season will insure greater overall success for your weed control program. Also using a two-pass program with a preplant or preemergence herbicide application limits the use of “rescue” herbicide treatments late in the season that can further stress soybean growth on previously injured soybeans.
3) Make timely POST applications. Many producers have been accustomed to controlling large weeds by increasing the rate of glyphosate in Roundup Ready soybean. Unlike glyphosate many of the POST herbicides used in non-GMO herbicides are not very effective on large weeds. It wasn’t too long ago when the application window for POST applications in soybean was between 2 and 4 inch tall weeds. So, remember when using a non-glyphosate based program herbicides need to be applied before weeds exceed 4 inches tall for adequate control. Applying a preplant or preemergence herbicide will also help extend this window by providing some early season control of these weeds.
4) Are herbicide resistant weeds a problem on your farm? There are several populations of ALS-resistant and triazine-resistant weeds around Michigan. If herbicide resistance has been a problem on your farm in the past take this into account when planning your weed control strategy in conventional soybeans. For example, if you have ALS-resistant common lambsquarters relying on a POST program of Harmony GT or Raptor would not control this weed. However, there are several soil-applied herbicides that can effectively control common lambsquarters season-long. To determine the effectiveness of herbicides on common lambsquarters and several other weeds consult the MSU Weed Control Guide for Field Crops (E-434) http://www.ipm.msu.edu/cat06field/06weedguide.htm.
For weed control in non-GMO soybean I strongly recommend a two-pass program that consists of a preplant or preemergence residual herbicide followed by a postemergence program. Using a two-pass program with a residual herbicide may add to the overall cost of your weed management program but this program will result in overall more consistent control of several weed species and help protect your soybean yields.
Dr. Sprague's work is funded in part by MSU's AgBioResearch.