When to harvest

Q: How do farmers know when to harvest corn?

A: There are a few different factors to figure when looking at when to harvest corn – those include maturity, weather and plant health, but most important is moisture content.
Corn harvest photo
As a general rule of thumb, farmers like to harvest corn between 15-25 percent moisture content. The variation depends on what they are doing with the corn and if they have a drying and storing facility on their farm.

Delivering directly to the grain elevator
Grain elevators prefer corn at 15 percent moisture content (which is optimal for storing corn without spoilage) – any higher and they will dock the price per bushel because the elevator will need to dry the corn to store it in their facility.

Storing at the farm to sell at a later date
If a farmer has a drying facility on their farm they can harvest at up to 25 percent moisture content and dry it down to 15 percent moisture to store in their grain bins and sell at a later date.

The best way to determine the moisture content is to take a few ears of corn out of different parts of a field, shell and mix them and put them into a moisture tester. The moisture tester will give a digital read of the moisture content.

You can also develop a good idea of the moisture content by knowing the different corn growth stages. Corn goes through six growth stages – you can read about and visually see the differences of each of those stages from Purdue Extension’s agronomy department.

Green corn   Corn near harvestCombine harvesting corn