Partially Flooded Soybeans
Chad Lee, University of Kentucky
Recent rains partially flooded several soybean fields across Kentucky. The risk of damage to soybeans is more of a concern for green plants. Soybeans that were brown or tan are less likely to be damaged. The following are some general comments.
Brown or Tan Soybeans
Any pods submerged for over 24 hours likely will lose the seeds, either from the seed rotting or from the pods shattering as they dry. Some seeds may sprout. Seeds that dry below 50% moisture and imbibe water to rise back above 50% can sprout. Rotted, shattered and sprouted seeds will not be suitable for harvest or sale.
Stem structure could be compromised. These plants were essentially dead. The material was drying out. Soaking in water can soften the stems and weaken them.
Mud from the flooding can coat the stems, leaves and pods. That mud can cause extra wear on the combine.
Harvest should occur above the flood line to avoid collecting damaged seed.
Any pods submerged for more than 24 hours are likely lost to harvest, either from shattering or rotting. Pods above the water line could develop seeds that look just fine.
However, premature death of these green plants could occur. Flooding pushes all the oxygen out of the soil. The root system will be compromised without oxygen. Soybean roots may not recover, which means the plants may not recover, either. If this happens, seeds may stay green and/or may shrivel. They may never turn to the proper harvest color and size.
Run the cutter bar above the flood line to avoid pulling in the damaged seeds. Keep harvested soybeans from flooded fields or areas separate from other fields.
The Food and Drug Administration says that “If the edible portion of the crop is exposed to flood waters, it is considered adulterated …and should not enter human food channels.”
So, keep flood-damaged seeds separate from the rest of harvest. Consider crop insurance options for areas where harvest does not appear to be reasonable.
Anonymous. 2016. Guidance for Industry: Evaluating the Safety of Flood-affected Food Crops for Human Consumption. Last Updated 07/01/2016 https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/EmergencyResponse/ucm287808.htm
Lee, C. J. Herbek, D. Hershman, and S. McNeill. Flooded Soybeans Nar Harvest. Corn & Soybean Science Newsletter. University of Kentucky. 2006:6,3 http://www.uky.edu/Ag/CornSoy/cornsoy6_3.htm#2
Timmerman, A. End of Season Flooding Effects on Soybeans, Harvest. 2017. University of Nebraska. 2017. https://cropwatch.unl.edu/2017/end-season-flooding-soybeans