Time for Corn Emergence
May 7, 2003 10(8):63-64
Joe Lauer, Corn Agronomist
In a planting date study conducted at Arlington, the first planting date of April
15 was beginning to emerge on May 7. For corn to emerge from the soil, it typically
requires about 125 GDUs where GDUs = ([Max. air temperature + Min. air temperature]/2)
â€“ 50. The accumulated GDUs to emergence varies by 15 to 60 GDUs due to a number
of factors like soil texture (fine: add 30-60 GDUs; coarse: subtract (30-60 GDUs),
seeding depth (add 15 GDUs for each inch below 2 inches), seed zone moisture (below
optimum add 30 GDUs), amount of residue on the surface (more than 75% residue add
30-60 GDUs), and hybrid differences for development.
On May 7, the coleoptile of about 50% of the corn plants was visible at the soil
surface. This particular field at Arlington required 22 days to emerge and as you
can see in Figure 1, emergence was right on schedule according to GDU accumulation.
Often in Wisconsin, I have seen corn take 28 to 35 days to emerge due to the cool
soil temperatures. In general, I do not get too concerned with slow emergence until
about 28 to 30 days have passed since planting. Most of the seed treatments used
today in corn production offer 45 to 60 days protection from many of the insects
and diseases that attack corn seedlings.