Fall Flooding Damage to Soybeans

Soybeans are very susceptible to flood damage in the fall, with lodging, shattering, and low quality grain being the most likely issues. Yield may be reduced by each of these problems.

• Lodging - Soybeans have little resistance to flowing water, so lodging is a likely result where water rapidly enters or leaves the field. Even non-flowing water can kill or weaken roots and leave soybeans susceptible to future lodging.
• Shattering - When soybeans are mature, splitting of pods and loss of seeds ("shattering") increases with repeated cycles of wetting and drying. Prolonged wetting due to submersion may amplify shattering losses.
• Grain quality reductions are inevitable with prolonged submersion of soybean pods. Issues include:
  • Sprouting in the pod if soybean seeds have dried below 50% moisture and imbibe water to increase back above 50% moisture (soybeans are very near to 50% moisture at physiological maturity, or growth stage R7).
  • Diseases may be introduced into pods and seeds by flooding. Diseased and discolored soybean seeds can incur dockages at the elevator.
• Yield losses can result from several factors:
  • Shattering before or during harvest
  • Severe lodging that limits harvest of plants or pods
  • Silt and debris that reduce harvest of lower pods
  • Sprouting and diseases that reduce seed weight
  • Damage to soybean plants prior to maturity, resulting in smaller seeds
    (see Appendix 1.)

• Scout fields thoroughly to identify the type and extent of flooding damage. Continue monitoring fields closely through the pre-harvest period to optimize harvest timing and minimize yield and quality losses.
• Manage field areas separately - Most fields will not be uniformly affected by flooding. Where practical, consider harvesting flooded and non-flooded field areas separately, as one harvest date may not be optimal for the whole field.
• Separate grain from flooded and non-flooded fields or field areas, as quality, storage life and marketing channels may be very different from these sources.
• Early harvest - Fields with severe flooding damage will likely benefit from early harvest to avoid further shattering, lodging and quality problems.