Growing Degree Days (GDD) and Rainfall Through July 31st

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

Most temperatures have been very conducive to pollination over the last two weeks, compared to late June/early July. Even in Sussex County we have only seen one day with a temperature of 90°F over the last week, and most nights below 72°F. Corn that was planted in April (and survived) is the most likely to have experienced excessive heat during pollination. Any fields you planted in early June, as late as that felt, are actually experiencing ideal temperatures for pollination right now. Rainfall is blocking sunlight, but bringing needed rain. This time higher rainfall is in the northern part of the state, with Newark starting to catch up to Delmar in total rainfall for this year. In our rainfall graph the dry period from about June 11 to July 15^th is very apparent, and will certainly affect yields in dryland corn. Still, with the range in dates most had to plant, some fields could still do well.

VT: 1135 GDD – Pollination can begin
R1: 1400 GDD – Silking, pollination
R6: 2700 – Blacklayer

Table 1: Accumulated growing degree days based on planting dates through July 31^st.