Heavy rain fell across much southern Minnesota on September 22 and 23 and left large areas of corn and soybean fields submerged. Flood waters covered perhaps 100,000 acres for several hours as rain water moved from fields into creeks and rivers. Longer term flooding of fields affected tens of thousands of acres of cropland.
Many factors will affect the quality of the corn and soybean crops following standing water. These include, but are not limited to: duration of the flooding, crop stage or maturity, depth of the water, movement of the water, and air and water temperatures. Fortunately, late-season rain events of this magnitude are relatively rare. Unfortunately, there is virtually no data to help us estimate crop losses and conditions of corn and soybean crops. Flood waters are thought to affect soybeans more than corn, and will therefore be our focus.
Potential flooding damage to soybean includes stem breakage and lodging, moisture-swelled seeds that can lead to pod splitting, seeds spouting or rotting, and contamination with mud. Short-duration flooding is gentler on the crop than floods that last several days or more, but one can be sure that flooding of any duration on any soybean field in late September will damage the crop to some extent.
Anecdotal information from flooding occurring in Mississippi in 2009 indicates that soybean fields that have reached full maturity (R8) at the time of flooding were found to have less damage than fields that were not yet fully mature (less than R7). So far, we have noted little loss from fields that were at R8 at the time of flooding and where ponded water receded in a few days. Significant lodging and loss is present where heavy stream flooding occurred.
The only management considerations that are open to producers at this very late date may be harvest timing and logistics. Rather than waiting for wet spots to dry, harvesting the non-flooded portions of fields first will speed harvest, minimize wear and tear on equipment and keep water-damaged soybeans separated from good quality grain.
Farmers should harvest and store soybeans from flooded areas separately from areas that were not flooded. Because damage levels are difficult to estimate and thresholds and allowances provided by grain elevators are unknown, it is critical that producers not mix damaged soybeans with clean ones. Do not be tempted to blend off a few bushels of damaged soybeans with a whole bin of good ones. The risks are simply too great.
Another reason to harvest flooded areas separately is related to crop insurance. It is important that producers clearly document these flooded areas so that insurance or disaster relief assistance claims may be made a later date. Isolating these flooded areas is the best means to document losses from these heavy rains. Producers affected by flood waters can get more information by visiting Extension’s flood and water website, www.extension.umn.edu/flood or direct questions to Extension’s Farm Information Line (1-800-232-9077). By Seth Naeve and Bruce Potter
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