Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu
Average soil temperatures in central Delaware have been a little warmer than the last two years, which may speed up germination a bit (Figure 1, yellow line). As of writing this on Wednesday, April 27, we are expecting some nights in the mid-30s, but very limited clouds during the day, which should keep soil temperatures warm. As you can see over the last month (Figure 2), very cold nights (air temperatures) have only dropped soil temperatures about 2°F over several days, and the same thing will probably happen this week. So I would expect slower germination April 27-29th, with soil temperatures still remaining above 50°F. This should have been a good week to plant, with scattered showers and warmer nights predicted for next week.
If you planted around April 15th, we have accumulated about 70 GDD as of April 27th, a little over halfway to emergence for corn. This year, with warmer temperatures starting on the 22nd, it will have paid off to plant earlier, although the best day appears to be around April 20th (Figure 3). Planting on the 22nd sometimes accumulates the same GDD as the 15th, but we haven’t observed that this year. We are still only accumulating between 0-15 growing degree units per day, so I would still expect most emergence to take 10 days.
Keep up with your regional conditions through DEOS (http://www.deos.udel.edu/).
Figure 1. Central Delaware soil temperatures over the spring of 2020-2022.
Figure 2. Minimum air and soil temperatures in Dover, spring 2022.
Figure 3. Growing degree days accumulated in each county if planted on April 15th and April 22nd in Kent County.