Growing Degree Accumulation and Rainfall Through July 22

Jarrod O. Miller, Extension Agronomist,; Cory Whaley, Sussex Co. Extension Ag Agent,; James Adkins, Irrigation Engineer,, Jake Jones, Extension Agriculture Agent, Kent County,, Dan Severson, Agriculture Agent, New Castle County,

Corn planted by late April has already gone through pollination and should be at the R2 stage, which can be identified by blisters (bumps) on the tips of the kernels, and the detachment of the silks. For a good overview of the reproductive stages of corn and how to identify them, see this post from Bob Nielsen ( While we have received steady heat units, temperatures have also been above ideal (87°F) for corn growth and grain fill, which may cause some delays compared to the GDD graph here. Warmer nights in the mid to upper 70s can also delay growth and cause issues for corn, although issues will not be readily apparent.

While this week’s storm went across the upper half of the state, rainfall accumulation has been better over the last month for Sussex and Kent Counties (Figure 2). This is an average for each county, and does not represent specific areas, which may receive different amounts than presented here. New Castle is currently at a 6-8 inch deficit compared to the rest of the state, although that deficit is built off of one very large event, which may not have infiltrated the soil for storage. Keep checking your irrigation and water budgets to make sure pollination and grain fill reach their maximum potential.

Figure 1: Growing degree day accumulation since April 15th.

Figure 2: Statewide rainfall accumulation since April 15th.