Brad Ross: What you need to know about corn


If you recall, in last week’s column I commented on the beautiful weather we were having. The weather was not only perfect for our Delaware County Fair, it was also conducive to many outdoor activities.

On my travels, as I was noticing combines harvesting corn, I was reminded of a story told to me by a coworker earlier this summer. Her family has an extensive vegetable garden, including sweet corn and several berry patches which they share with friends and family.

A friend was helping herself to sweet corn and asked my coworker how long the sweet corn would keep growing. The friend was shocked to learn that each stalk produces one edible ear and, once that ear is perfect for picking and eating, the corn plant has done its job for the year! She was under the impression that each corn plant kept producing additional ears until frost. That story led me to write this article: Corn Class 101.

Corn is an annual grass. Nearly all the corn you see is field corn used to feed livestock, fuel cars and make a variety of products, such as plastics, starches and adhesives. Field corn is also processed to make food products, such as chips, tortillas, corn oil and corn syrup. Only a very small percentage of corn in the United States is sweet corn. Sweet corn is picked when the plant is still green and the kernels are succulent and flavorful. Field corn is harvested much later in the summer, usually beginning in September in our area, and by then the corn looks brown.

Field corn goes through several growth stages. First is the blister stage when the developing kernels look like whitish “blisters” on the cob. Next is the milk stage when the kernels are mostly yellow, full of liquid and, when squeezed, emit a milky fluid.

Then it goes to the dough stage where the milky fluid in the kernel becomes a bit more solid. From dough, the corn matures into the dent stage where the kernel is indented at the part of the kernel closest to the husk. Physiological maturity is signified by a “black layer” located where the kernel attaches to the cob. As the corn goes through these stages, the kernels change from about 85 percent moisture in the blister stage to roughly 30 percent in the black layer stage.

Moisture content is extremely important because corn can be safely stored at about 15 percent moisture. Grain purchasers base their pay on the moisture of the corn when it is delivered. Higher moisture corn means the grain purchaser has to spend money to dry it and therefore docks the producer accordingly.

In a perfect world, every farmer would dry the corn on the stalk in the field to get as close to 15 percent moisture as possible. The reality is that weather conditions strongly influence in-field grain drying. Warmer temperatures, sun, low humidity and light winds provide the best grain-drying conditions. Too much wind can knock the corn to the ground, making it difficult for the combine to pick up, resulting in significant losses. Too much rain means the corn moisture stays high and causes delays because no harvesting can be accomplished until the soil dries.

Corn may dry one point of moisture per day or more under favorable conditions and conversely, corn may not dry at all on a cool, rainy day. To make up for unpredictable weather, many farmers invest in grain bins and dry their corn themselves using propane or natural gas.

So as you walk, bike or drive past the corn fields in Delaware County, take a minute to appreciate the scenery and all that that goes into the growing of the simple corn plant. For more information on Delaware County’s natural resources, visit our website at

Brad Ross

Contributing columnist

Brad Ross is communications specialist at the Delaware Soil and Water Conservation District. He can be reached at [email protected].

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