Agronomy Talk

Agronomy Update

E.Indiana and Ohio: When Will My Corn Be Ready to Harvest?

Published on Monday, September 8, 2014

We are finishing up the first week of September and harvest will be here soon.

Step 1: How many days till your corn is “black layered”? ​
It takes 20-25 days for corn to get to black layer after it dents. If your corn is dented and showing a milk line half way down, then you are looking at 16-20 days till black layer.

Corn Maturity is a process driven by GDUs (heat units) so more heat and it will progress quicker; cooler temperatures prolong the process.

Step 2: How fast will it dry down after black layer?
This one is a big “if” based on how much heat you get after black layer. Corn grain moisture at R6 (black layer) is initially about 33 percent.
Early maturing corn will have warmer days and dry down quickly. Later planted corn or late maturity hybrids that don’t black layer until close to frost time will dry down slowly, simply because heat unit accumulation in late October and later is very slim.

Corn dries down one percent moisture per day in September.
In October those rates drop to ¾ percent and ½ percent. In late October to November you will only dry down ¼ percent per day depending on the weather.2

The way things are progressing, September will have some early planted corn harvested in Ohio especially in regions that have turned off dry late in the summer.

In a few weeks I will discuss at what moisture to begin corn harvest to get the best yields and why.



          Remove the tip of the kernel to reveal if it has reached R6-Black Layer-Physiological maturity.

Below is a helpful chart for the relationship between kernel growth state and development.

                                                    (Source: Wisconsin University)

Related Reading:
1. Grain Fill Stages in Corn - Purdue University Department of Agronomy

2. Corn Drydown – What to expect? Ohio State University


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Alex Johnson

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