End of Season Flooding in Soybean

  • Late-season flooding can be detrimental to a soybean crop with potential yield reduction and seed quality.
  • Damage to the soybean crop can vary depending on the crop growth stage at the time of flooding, how long the crop remains under water, and the soil type.

Effect on Yield Potential

Flooding that occurs during the early soybean reproductive stages is more detrimental than flooding in R6 stage and beyond. Flooding at the beginning of flowering (R1) can cause potential yield losses of 2.3 and 1.5 bu/acre on clay and silt loam soils, respectively.1 Potential yield loss would be expected to be greater in soybeans at beginning pod (R3) to beginning seed (R5) stages. Stages R3 to R5 are critical to soybean yield potential as pods and seeds are set and developed. Stress occurring at R7 or later generally has minimal effect on yield potential compared to stress at earlier growth stages.

Other Effects of Flooding

It is difficult to predict the yield effect of flooding late in the season. However, there are several scouting and management considerations to keep in mind as harvest approaches:

  • Pod shattering. Shattering of the pods may occur when the soybean plants dry out.2 Marking these fields for early harvest may be necessary once the seeds have dried enough for harvest.
  • Plant lodging. Lodging can occur from water rapidly entering and leaving the field. If lodged plants come in contact with the soil or mud, pods may fall to the ground and/or seed quality may be reduced. Harvesting slowly may reduce loss.
  • Silt and mud. When fields dry out, soil may remain on the plants. This can delay drying of the plant and cause dusty soybeans at harvest. Rain could wash some of the soil off of the plant. Additionally, waiting to harvest the soybeans until last could keep the combine cleaner for non-flooded fields.
  • Sprouting in the pod. Beans that have dried to less than 50% moisture and then take in water again to rise back above 50% moisture may germinate.2 There is no solution for this scenario.
  • Fungi. Certain fungal diseases can thrive with warm and moist conditions during soybean maturity. Phomopsis seed decay, which occurs when the fungus that causes pod and stem blight infects the seed, can affect germination.3 Anthracnose is another common pathogen and may cause smaller seeds. There can be other pathogens present that simply flourish by degrading soybean tissue and are not harmful to germination. Several of the fungal diseases can cause black dust during combining.
  • Grain quality. Prior to harvest, check the quality of the grain. Flooded fields may have reduced seed quality that can affect marketability.
  • Soybeans may not mature. Fields that did were flooded prior to R7 growth stage for more than 24 hours, will most likely die prematurely.2 Reduced seed quality can be expected.