Growing Degree Days (GDD) and Rainfall Through July 2nd

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu

Since some have chosen to replant corn fields I have added the first half of June’s GDD. Most corn planted in June should be close or ready to side-dress any additional nitrogen. There should be tasseling across the state in our earliest planted fields, and this is possibly occurring on some very short corn. High temperatures and moisture stress will be an issue during this stage, so add that to your list of possible yield reducing factors this year. Here are the GDD needed to reach these corn stages:

V6: 475 GDD
V12: 870 GDD
VT: 1135 GDD
R1: 1400 GDD

From the rainfall graph you can observe what is very apparent, many dryland fields are in need of rain. Although Georgetown has received 20 inches of rain since April, its moved on down into the profile or into the watershed, and the soil surface is fairly dry. For those who say the east coast is lucky with our annual rainfall accumulations, remind them that timing of that rain is more important.

Table 1: Growing degree days accumulated through July 2nd from the beginning of each week.