Is It Possible to Manage Stress in Soybeans?

Dan Davidson, Agronomist PhD, CPAg, CCA

Learning to recognize, manage and preempt stress is an important and perhaps undervalued key to higher yield.

All plants experience some degree of stress during the season, and it is hard to avoid completely, even when the crop looks green and healthy. Some stresses nip away at yield without showing visual symptoms.

There are two types of stress, abiotic and biotic. Both reduce growth and yield.

  • Abiotic stress is caused by nature and includes drought, water saturation, heat, wind, abrasion by sand and soil particles, low temperature frost, salinity or sodicity, or metal toxicity (Al, Fe and Mn toxicity and acid pH).
  • Biotic stress is caused by living organisms, such as bacteria, viruses, fungi, parasites, beneficial and harmful insects, weeds, or even other cultivated or native plants.

 

Plants respond to abiotic stress such as heat and drought by closing down stomates, curling up leaves, slowing down metabolizing to conserve water and energy and accumulate sugars (like antifreeze) to increase tolerance to cold. Management practices to curtail abiotic stress include:

  • Irrigating to remediate water shortages and drought
  • Adding tile drainage and deep tillage to improve drainage and water movement through the profile
  • Liming soil to raise pH to reduce solubility of toxic metals
  • Adopting no-till and cover crops to build soil, reduce evapotranspiration and conserve soil water
  • Applying gypsum as a source of calcium to displace high levels of sodium
  • Adopting aerial fans in citrus groves to create air movement and reduce the risk of frost

 

Biotic stress has a different response. Plants interact with pathogenic and symbiotic microorganisms by either forming a mutual dependent relationship with them or activating a plant defense system in response to pathogens. For example, rhizobia bacteria infect plant roots, instructing them to build nodules for housing. The plants provide minerals and sugar to the rhizobia, which in turn provide nitrogen back to the plant. This is a symbiotic and mutually beneficial relationship. Plant roots and mycorrhizae form a similar relationship.

Plants have evolved defense responses to biotic stress based on biochemical stress triggers that initiate a response. Insect wounding and feeding or disease infection can trigger production of compounds that seal a wound or fight off an infection. There are many examples in the scientific literature describing how plants respond to a biotic stress. These responses may not be as efficacious as a fungicide application, but in some situations, it may keep plant responses below a chronic and damaging level.

Management practices can minimize damage caused by biotic stress factors, including:

  • Developing resistant or tolerant plant varieties
  • Applying insecticides or fungicides
  • Planting in a window to reduce risk of disease infection or insect infestation (planting later to reduce SDS or planting wheat after the Hessian Free Fly date)
  • Creating soil conditions that improve drainage and drying to abolish a habit for diseases
  • Planting soybeans or dry beans in wider rows to increase aeration and reduce risk of white mold
  • Allowing natural insect predators to flourish to keep economic pests at bay (e.g. natural predators have greatly reduced the risk of a soybean aphid outbreak)
  • Keeping plants healthy and growing vigorous with the right fertility and nutrition program
  • Applying biological and other commercial products that remediate or prevent stress or stimulate growth and the “stay-green” characteristic

 

Stresses are part of everyday farming. Some are caused by uncontrollable factors like weather and just plain bad luck (wrong place and time). However, many stresses are controllable and either preventable or treatable. As a farmer, always know your crop, what stresses it is at risk from, and what you can do to prevent or remediate stresses. Understanding this important key to effective crop management can help you be more stress-free in the upcoming seasons and increase your yields for greater profitability.

Fortalis® is an essential crop input

Your soybean yields can also benefit from Fortalis®, an advanced crop enhancement foliar spray that works by mobilizing calcium already existing within plant tissues, resulting in higher pod retention. When applied as a tank mix, Fortalis® with a fungicide or insecticide contributes to better plant health and higher yield potential. It’s an essential crop input that you need to get the most out of your crop.

Dan Davidson is a PhD agronomist, part-time farmer and soybean expert from Nebraska who consults with soybean checkoff and industry on crop production, marketing, and product development projects.

 



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