Heavy rain fell across much southern Minnesota on Sept. 22 and 23 and left large areas of Minnesota corn and soybean fields submerged. Floodwaters covered nearly 100,000 acres for several hours as rainwater moved from fields into creeks and rivers. Longer-term flooding of fields affected tens of thousands of acres of cropland. In most instances, drainage tile, where present, was unable to prevent ponded waters. In other cases, streams swollen by 4-12 in. of rain falling on fields, roads and cities came out of their banks and flooded fields.

 

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 estimate crop losses and conditions of corn and soybean crops.

Floodwaters are thought to affect soybeans more than corn. 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. We do know that short duration flooding events are gentler on the crop than floods that last several days or more. While little is known about crop stage effects on flooding damage, one can be sure that flooding of any duration on any soybean field in late September will cause damage to the crop. The extent of this damage is unknown.