By Gared Shaffer, Extension Weeds Field Specialist
Many emotions set in on farmers that hear the word “non-GMO,” but it could help them in times like today when prices are low for many farm products in South Dakota.
As some may already know, non-GMO soybeans are being contracted in South Dakota at Miller by the South Dakota soybean processors. What could this mean for growers? It may mean a niche market for soybean growers to make a little more per acre when higher crop prices are needed. Some markets suggest that non-GMO soybeans can fetch a dollar or more a bushel than GMO soybeans.
The big question that comes to mind with non-GMO soybeans is weed control. Is it possible to continue to farm no-till and plant non-GMO crops with resistant weeds growing in your fields? The answer is yes — with a little more homework, a grower can control weeds and keep his soil healthy.
Non-GMO Soybean Weed Management
These management strategies are not uncommon even in GMO soybeans. The basics are the same. First, we always need a weed-free start at planting. This means do not plant unless the weeds prior to planting are controlled. To give you some time for a post application and to give your soybeans a head start, make sure to apply a pre-emergence herbicide before planting. Then apply if needed a post-emergence herbicide application when weeds are less than 4-6 inches tall after soybean emergence, which may be anytime between 2-6 weeks after soybean emergence.
Burndown Herbicide Options
I can’t stress this enough with any crop, but you need to start with a clean field before planting. To do this, use a burndown herbicide that controls a broad spectrum of weeds, such as glyphosate, paraquat or glufosinate (Liberty) before or at planting. Other herbicides that may add in weed control could include 2,4-D ester and a metribuzin product.
Pre-Emergence Herbicide Options
The biggest decision here is to choose herbicides that will give you a window to control early weeds and give your soybeans a head start. Examples of herbicides that may give you the best control, depending on what weed pressure you have, could include: Authority Assist, Authority First/Sonic, Canopy, Valor XLT, Gangster, Metribuzin, Python, Scepter and Valor.
Post-Emergence Herbicide Options
It is best that weeds be controlled from 2-4 inches tall, but never allow them to reach over 6 inches tall. Also, use a spray volume of at least 15 gallons per acre and nozzles that produce medium-sized droplets. Some options:
- Flexstar or Rhythm + Select, Fusion, etc. (grass herbicides) + COC or MSO + AMS
- Other options could include FirstRate, Classic or Synchrony. If applied with 28% nitrogen, this may improve weed control but also increase crop injury.
- If necessary for late-emerging weeds, apply Phoenix or Cobra 3 weeks later. If troublesome broadleaf weeds exists, add a grass herbicide if late-emerging grasses are a problem.
Applications of herbicides in the fall are not as long lasting or effective compared to those applied in the spring. Never substitute a fall treatment for a spring treatment. There are options for fall application but usually they end up costing more and then a spring application is almost always necessary. One combination that may be an option in the fall may be glyphosate and 2,4-D or 2,4-D and a low rate of a chlorimuron-containing product.
There are options that increase cash crop growth and decrease weeds as well. Those include crop rotation, cover crops, row spacing and livestock integration.