Importance of Warm Soils at Planting
From AgVenture's Seeds for Success Agronomy Update, March 2016
Less than ideal stands result from planting into cold, wet soils or directly before a cold or wet weather event, resulting in significant stand loss. But cold and wet snaps are often inevitable. The chances of establishing a good stand are greatly improved if hybrids are allowed to germinate at least 1-2 days in warmer, moist conditions before a cold-stress event. Hybrids with a higher stress emergence score can help moderate stand losses due to cold stress.
One reason why temperature during imbibition is critical to corn emergence is the fact that seed imbibes most of the water needed for germination very rapidly. To illustrate the rapid timing of water uptake, seed was submerged in 50 F water for 3 hours and weighed at intervals of 30, 60, 120 and 180 minutes to determine water uptake.
Seed imbibes the most water within the first 30 minutes after exposure to saturated conditions. If this early imbibition occurs at cold temperatures, it could kill the seed or result in abnormal seedlings. Growers should not only consider soil temperature at planting, but also the expected temperature when seed begins rapidly soaking up water. Seed planted in warmer, dry soils can still be injured if the dry period is followed by a cold, wet event (sources: AgVenture and Pioneer).