The general consensus is that for proper germination of corn and soybean seeds, we should have a minimum soil temperature of 50 degrees Fahrenheit. But what happens when we plant into soils that haven’t yet reached that threshold or when a period of cold, wet weather follows soon after planting?
We certainly risk susceptibility of the seed to imbibitional chilling injury. Imbibition is the uptake of water by a newly planted seed. In corn this happens usually during the first 24-48 hours after planting, assuming the soil is moist. For soybeans, imbibition usually occurs within 24 hours of planting.
If the seed receives a “cold drink” of water during this phase, cells in the seed can rupture. Corn roots and shoots may not develop properly, and cell membranes are not hydrated properly in soybeans. Much of the research is not clear-cut as to how long the seed needs to be exposed to sub-50 degree soil temperatures.
But if the seed is planted and soil temperatures are below 50 degrees during the first 24-48 hours chilling injury is possible. Once seeds have imbibed their needed water, if soils drop below 50 degrees, emergence may be delayed, but chilling injury should not be a factor.
At this point, there is really nothing that can be done for corn and soybeans that are already in the ground. If you have planted corn or soybeans and experienced a cold rain and/or prolonged cold soil temperatures, you will want to scout your fields for possible emergence problems.