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Agronomy Update

Managing Continuous Soybeans

Published on Thursday, February 16, 2017

Over the past few seasons, soybean yields as a whole have been pretty impressive. As a strategy to combat lower grain prices, many farmers are taking a closer look at soybean after soybean, or even continuous soybean, rotations. This is especially true for farmers with acres that may not always be best suited to grow corn. Some things to think about when considering a soybean after soybean scenario are fertility, disease management, planting rate, and weed control. 

Fertility & pH

Soil fertility is the foundation of any successful crop. When growing continuous soybeans, taking soil tests are a great way to determine where your fertility values are and what your application rates should be.

  • Maintaining a soil pH at or above 6.5 is ideal to get started on the right foot.
  • Soybeans in general are more responsive to pH than corn, so if your soil samples call for lime, making that application can be imperative to soybean success.
  • Soybeans are voracious feeders of nutrients and a 60 Bu./A. crop can remove up to 90 lb. of potassium and 50 lb. of phosphorous. This is equal to approximately 100 lb. of 18-46-0 and 150 lb. 0-0-60. At the very least, these rates should be applied to replace what was lost to the previous crop.
  • If you normally plant a corn-soybean rotation, fertilizer applications are often only made ahead of the corn crop. In light of how much fertilizer soybeans use, fertilizing ahead of your soybean crop is a great idea.

Foliar Disease Management

One disease that has become more prevalent over the last few years is Frogeye Leaf Spot. Given its prevalence in recent years, Frogeye is one disease to be on the lookout for in 2017 on those continuous soybean acres. Scout often and consider applying a fungicide and insecticide at the R3 growth stage, which has proven to provide a $17/A. ROI in Beck’s Practical Farm Research (PFR)®. 

Seed Treatment

When growing a continuous crop, we have the potential to ramp up the inoculum in the soil of certain diseases that can attack that crop. When growing continuous soybeans, protecting your seed from diseases such as Fusarium, Rhizoctonia, Pythium, and Phytophthora can mean the difference between having to replant and growing a successful soybean crop.

Beck’s Escalate™ seed treatment contains a unique blend of fungicides, insecticides, biologicals and/or a biostimulant that are sealed on the seed with polymer coating to offer improved stands and higher yields. And by adding ILeVO® fungicide to the standard Escalate mix, Escalate SDS provides an additional layer of protection for farmers looking to push earlier planting dates or those facing sudden death syndrome (SDS) in their fields. Beck’s PFR has shown that Escalate SDS is a PFR Proven™ product, providing an average $11.48 return on investment (ROI) over three years. 

Planting Date & Seeding Rate

While these topics are separate, they are actually related when it comes to soybean planting. Planted population and canopy coverage can have an effect on weed control. Earlier planted soybeans at a lower seeding rate will naturally branch more and will benefit from having more space to stretch out. This will reduce the competition between plants, allowing them to grow out rather than up.  

Beck’s 10-year PFR Proven data has shown that planting soybeans before May 15 at the economic optimum seeding rate (EOSR) of 100,000 seeds/A. has generated the greatest ROI of $150/A. By lowering seeding rates, especially on those early planted acres, we have the ability to lower seed cost and improve yield. If weather becomes a challenge and planting is pushed to later spring, increase your seeding rate for every week you are delayed until you finish planting. A good rule of thumb is to increase your seeding rates 10,000 seeds/A. for every week you are delayed past May 15. 

Weed Control

Some of the hard to control weeds such as waterhemp, marestail, and Palmer amaranth are glyphosate and PPO resistant so we will need to implement an effective weed management strategy. Whether you use Roundup Ready 2 Yield®, LibertyLink® , or the new Roundup Ready 2 Xtend® soybeans, the foundation for any weed control system should be a good residual program. 

Although many weeds are showing resistance to the post-emergent PPO chemistry, PPO soil residuals can still provide control of broadleaf weeds. The main concern with these products are the cool, wet soil conditions that can cause crop response. Consider using multiple residual chemicals to better prepare for different situations. For example, I might consider a residual product for early planted soybeans that is less likely to cause herbicide injury when the weather in southern Illinois inevitably turns cool and wet. But as the season progresses, I may switch to another product with a strong residual once the weather warms up. Layering residual chemistry is another great option. 

If you can control multiple weed flushes with residual chemistry, this will place less of a burden on the post-emerge chemistry, such as Liberty® or the new dicamba products Engenia™ or Xtendimax™. Depending on which system you choose, these herbicides work well on the hard to control weeds, but having the residual in the system is a must, to ensure that you continue to have these products in your weed management toolbox!









Practical Farm Research (PFR)®, PFR Proven™, and Escalate™ are trademarks of Beck's Superior Hybrids, Inc. ILeVO® and LibertyLink® are registered trademarks of Bayer. Roundup Ready 2 Yield®, Xtendimax™ and Roundup Ready 2 Xtend® are registered trademarks of Monsanto Technology LLC. Engenia™ is a trademark of BASF Corporation.

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Sean Nettleton

Sean Nettleton

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