Current Soil Temperatures and Corn Planting

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu

The preferred soil temperature for corn germination is 50°F, which allows the seed to begin root and shoot growth. When soils fall below this temperature, germination may be limited and seeds may rot in the ground. Many of the weather stations on DEOS (http://www.deos.udel.edu/) have soil temperature as an option, so you can track current conditions. Soil temperatures have been consistent across the state, ranging from 47-63°F in Newark, Dover, and Georgetown, even as air temperatures have ranged from 34-77°F. Soils are a pretty good insulator, and will not change as rapidly as air temperature. A slower change in soil temperatures will occur when they are saturated or have additional cover from crop residues or no-till. So be sure to check the soil temperatures at each station, and not just rely on local air temperatures.

While predicted highs over the next few days are in the 50s to 60s, nighttime temperatures could be in the 40s or lower. Consider that even if seeds survive, germination will be delayed, and won’t necessarily get you ahead. In Georgetown last year, corn took 10 days to emerge when planted April 24th, 8 days to emerge April 30th, and only 5 days to emerge May 16th. Considering that planting decisions also hinge on moving equipment and balancing all the field work that needs to be done, planting earlier may be necessary. But if there is still time to wait, letting soils warm up will improve chances of germination and higher stand counts.

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