Growing Degree Days (GDD) and Rainfall Through August 12th

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

With the variable planting dates we had this spring/early summer, you should get plenty of practice recognizing the different reproductive stages of corn during grain fill. Any field planting through mid-June should have started the reproductive stages with silking and pollination. Most fields planted in April or early May should be in the dent stage, with everything else in between. If you want a good overview of corn reproductive stages, check out this article from Dr. Bob Nielsen at Purdue: https://www.agry.purdue.edu/ext/corn/news/timeless/grainfill.html

Rainfall has been the steadiest all summer, with pop up showers in between a few days of sunshine. There have more nights above 72°F this August and a few days with highs in the 90s, so corn pollinating right now may have some issues. Remember that corn plants still need rain throughout the grain fill period, so don’t shut off your irrigation yet.

R1 (Silking): 1400 GDD
R2 (Blister): 1660 GDD
R4 (Dough): 1925 GDD
R5 (Dent): 2190-2450
R6 (Blacklayer): 2700

Table 1: Accumulated growing degree days based on planting dates through August 7^th.