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Evaluating hail injury to soybeans.

Agronomy Bulletin 51 ─ Soybean Hail Damage

Situation

Hail storms can have varying impacts on soybeans each year. Accurately assessing the situation can help you estimate potential yield loss.

Factors to Consider

  • Growth stage
  • Leaf defoliation
  • Stand loss
  • Pod damage
  • <a href="http://www.rma.usda.gov/policies/2013policy.html" target="_blank">Crop insurance</a>
Indeterminate soybean defoliation percent of damage

Action Plan

  1. Allow recovery time. If applicable, contact your crop insurance agent and wait three to five days before assessing damage. Waiting allows for regrowth on healthy plants to help achieve a more accurate evaluation.
  2. Identify growth stage. Most agronomy professionals utilize the growth staging system developed by Iowa State University (ISU). For soybeans in the vegetative stage, the crop insurance industry counts the unifoliate node and all nodes above that have a fully developed trifoliolate leaf present (or missing). A trifoliolate leaf is considered fully developed when it unrolls and the leaflet edges no longer touch other portions of the leaf. Example: a plant with unifoliate leaves and a fully developed trifoliolate leaf at a node above the unifoliate is considered V2. This system typically results in one growth stage higher than the ISU system. For reproductive stages, all use the ISU system.
  3. Assess stand loss. Soybean fields should be evaluated after early season hail storms for a possible replant. For stand losses and pod damage later in the season, refer to the Soybean Loss Adjustment Standards Handbook.
  4. Estimate yield loss from leaf defoliation. Leaf defoliation can reduce yield by decreasing leaf area needed for photosynthesis. Estimate yield loss by calculating the percent of leaf area removed from the plant and/or leaf area that is no longer green. Remaining green leaf area, even if torn, should not be considered destroyed. Evaluate leaves on plants in multiple sites to get an accurate estimate of leaf area lost. Research shows that leaf area loss during vegetative stages of growth has minimal impact on yield. For indeterminate soybeans utilize Table 1. For determinate soybeans, refer to the Soybean Loss Adjustment Standards Handbook.
  5. Estimate damage to stems. To determine yield loss due to stem damage, evaluate both stems cut off and stems broken over. Refer to Table 2.
Soybean stem damage assessment

Summary

To evaluate soybean yield loss from hail, wait for the plant to show regrowth and consult your crop insurance agent before making any decisions. Once the growth stage is identified, estimate yield loss by combining losses from stand reduction, leaf defoliation and stem damage.

Resources

*If more than 65 percent of the nodes are cutoff or broken over, it is impossible to predict the percentage of loss that may result. Growing conditions following the damage will dictate the extent of recovery that may occur.

Published on Friday, July 26, 2013