Early April planted corn is slow to emerge leaving growers asking when will corn emerge? As of Monday, April 27, only 120 growing degrees units (GDUs) have accumulated from the first full week in April measured at the MU Buchanan County Extension weather station. The week of April 13 had low temperatures and only five GDUs were accumulated. Corn needs 120 GDUs to emerge from the soil.
The low April temperatures slowed corn emergence. Agronomists use growing degree units (GDUs) to estimate emergence and corn growth, which is based on the daily high and low of air temperatures.
The high and low temperatures are added together, then are divided by two to find average, then subtracted from 50. If the average high temperature in summer is greater than 86, the high temperature will remain at 86 as this is the maximum growth rate of corn.
Planting depth, tillage, crop residues and soil moisture are factors that may slow or speed corn emergence and influence the number of GDUs required for emergence.
As we move into the first week of May and air temperatures increase, the time needed for emergence will decrease and be typical of normal corn planting.
Scout early planted corn for emergence and adequate stands. When corn seeds are in the soil for a long time, there is a greater opportunity for pests and weather to reduce stands.
For more information, contact Wayne Flanary, Field Specialist in Agronomy at 816-279-1691, University of Missouri Extension.