From Bruce Steelman, UT Extension Office
We keep sliding back into a ‘below normal’ temperature pattern for April, and close to freezing temperatures with rain in this week’s forecast has created some concern about viability of corn and soybeans planted this week. Based on current weather reports, nighttime temperatures are forecasted to be close to freezing Tuesday and Wednesday night with some rain expected Tuesday in west Tennessee. Any time soil temperatures drop below 40 degrees, there can be a severe impact on corn and soybean seed planted prior to the cold temperature. Corn and soybean seed are actually sensitive to soil and soil water temperatures below 50 F during the first 36-48 hours of planting (corn) or 24 hours of planting (soybean). Seed planted into moist soil will start to imbibe water quickly. ‘Imbibition’ (rapid water uptake) under cold conditions during the critical first hours of germination can lead to nonviable seed and aborted growth of the radicle (root) and shoot/seedling. Chilling injury while imbibing water is more likely to occur when the field receives rain on top of cold temperatures, or in saturated soils. By about 48 hours after planting, both corn and soybean seed absorb water through a slower process known as osmosis and are less susceptible to chilling injury when soil temperature drops below 50 F for brief periods of time. Germination may be delayed but should still occur. Consider hitting the pause button on corn and soybean planting, wait for this system to pass through and soil temperatures to improve. Nighttime temperatures are projected to be better on Friday and the weekend, but not actually back above 50 F for consecutive days until next Monday (the 26th).