Heather Darby and Sid Bosworth, Extension
Assistant Professor, UVM Extension - Northwest Region and Extension Associate
Professor, Department of Plant and Soil Science, University of Vermont
Once the corn is planted germination and emergence is driven by temperature. Since corn’s growth rate is dependent on temperature, its rate of development can be characterized using a system called growing-degree days (GDD). To figure the daily GDD, use the following equation: Daily GDU accumulated = ((daily high temp. + daily low temp.)/2) - 50. The daily GDD are summed to report accumulated GDD over some time period (i.e. GDD from planting to emergence).
Typically corn requires between 110-130 accumulated GDD before emergence will occur. The number of GDUs to emergence can vary by 15 to 60 GDD due to variation in field conditions. For example, a fine texture soil may take an additional 30 – 60 GDD whereas coarse soil may take 30 – 60 less GDD.
A source of information that reports Growing Degree Days is the Northeast Ag Statistics Service out of Nashua, NH. You can get a weekly Crop/Weather Report from their website at http://www.nass.usda.gov/nh/.
In general, 125 GDD equates to approximately 22 days. We would probably not be overly concerned with slow emergence until about 28 to 30 days have passed since planting. After this duration one may want to consider replanting as an option. As corn emergence is delayed the seed becomes increasing vulnerable to attack by soil-borne insects and diseases. Additionally, slow germination and mesocotyl elongation increases the risk of underground leafing out due to soil crusting. Soil crusting can be alleviated by rotary hoeing the field. When the corn finally does emerge it will take an additional week before nodal root development occurs at the crown of the seedling. Until these roots develop, corn seedlings are extremely vulnerable to damage from disease, wireworm, seedcorn maggot, and white grub. When emergence is delayed, it is extremely important to be walking the fields and looking for these potential problems described above. Scouting corn soon after emergence can be very helpful in identifying problems while they can still be managed.
This site is maintained by Sid.Bosworth@uvm.edu, Plant & Soil Science Department, University of Vermont.
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