Corn Planting Starts but Soil Temperatures Slow Germination
Soil temperature data at Graves Chapple Demonstration Farm and Hundley-Whaley Farm weather stations have been in mid-40s as of Thursday, April 9th. Early planted corn will be slow to emerge at these temperatures.
Growing degree days (GDDs) base 50 which is used to measure how fast corn grows has accumulated about 78 degree days at Graves Chapple and 62 at Hundley-Whaley. Corn requires about 110 GDDs to emerge but can range from 90 to 150 GDDs. The accumulation starting point is the corn planting date. Then the GDDs are measured from that point on.
This data is available on the web from each of the weather stations under weather indices and is already calculated for you.
To determine daily GDD accumulation on your own, calculate the average daily temperature (high + low)/2 and subtract the base temperature which is 50 degrees F for corn. If the daily low temperature is above 50 degrees, and the high is 86 or less, then this calculation is performed using actual temperatures, but if the low temperature is less than 50 degrees, use 50 degrees as the low in the formula. Similarly, if the high is above 86 degrees, use 86 degrees in the formula.If it takes a corn hybrid 100 GDDs to emerge, and daily high and low temperatures average 70 and 50 degrees following planting, 10 GDDs accumulate per day, and corn should emerge in about 10 days (100 GDDs to emerge/10 GDDs per day = 10 days). However, if daily high and low temperatures are cooler, averaging 60 and 45 degrees after planting, 5 GDDs accumulate per day, and it may take nearly 3 weeks (100 GDDs to emerge/5 GDDs per day = 20 days) for corn to emerge.
Seedling emergence is dependent on soil temperature and air temperature. Also, keep in mind that estimates of emergence based on GDDs are approximate and can be influenced by various factors including residue cover, tillage and moisture content. Corn emergence can be slowed by inadequate soil moisture.
Crops vary widely with regard to the minimum moisture content required for emergence. For corn, the minimum moisture content at which the radicle emerges is 30% of the seed dry weight. In contrast, for soybean, the reported minimum moisture content required for germination is 50%.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.