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Evaluating sodden soybean fields after flooding.

Agronomy Bulletin 96 ─ Flooded Soybeans

Temperature, timing and soil type can affect soybean loss after flooding.

Situation

Waterlogged and completely submerged soybean plants can significantly reduce yields. When dealing with flooded soybeans, take into account the following conditions that can damage the crop.

Factors to Consider

  • Flood duration
  • Temperature
  • Rate of drying
  • Growth stage
  • Disease

Action Plan

  1. Take into account the duration of the flood. Soybean plants can tolerate being fully submerged for up to 96 hours, depending on various conditions. After that, stands and vigor are dramatically reduced, making it hard for the crop to fully recover. Waterlogged soybeans, in which only the roots are submerged, are less affected by flooding.
  2. Be aware of soil oxygen levels. Soybeans require ample soil oxygen to perform efficiently. Flooding limits the amount of oxygen available to the soil, and thus the plant. Without oxygen, the soybean plant is unable to perform important functions to survive, like respiration.
  3. Keep in mind cool temperatures are ideal for survival. Respiration also is affected by the temperature of the flooding water. Higher water temperatures increase the speed of respiration, which reduces the amount of oxygen in the soil available to the plant. With less oxygen available, the plant will begin to rot. Cooler water temperatures slow the rate of respiration and decrease the chance of yield loss.
  4. Know your soil type. The faster the soil dries after flooding occurs, the less likely the soybean plant will be damaged and yields will be affected. Flooded clay soils take longer to dry than silt loam soils; therefore, field soil types often can affect damage in flooded soybeans.
  5. Consider replanting. Flooding is most harmful during the early reproductive phases of soybean development. Consider replanting if your crop floods during this stage. Be sure to consult your crop insurance agent when making replant decisions.
  6. Evaluate other flooding effects. Soybeans that survive flooding are more likely to develop root diseases, nitrogen deficiency and other plant nutrient imbalances. Scout fields after flooding to prevent any of these conditions from worsening.

Summary

Based on the duration of flooding, temperature of the water and soil drying rate, injury to soybean plants after flooding can be minimal to quite extensive. It is important to scout soybean fields after flooding to diagnose the condition of the crop. Consider replanting when damage is severe. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Published on Sunday, June 15, 2014