Observable Differences between Corn and Sorghum Early in the Season
Dec 2022 MAFG/HP
Brent Bean, Sorghum Checkoff Agronomist
When I first started my career as a newly minted Ph.D. agronomist, during the early part of the season, I could not readily tell if a field was planted in corn or sorghum, especially from the road and that is one thing that always bothered me. Even more distressing, is that even standing in the field, I was not always sure and would have to resort to digging up a plant to see if it originated from a corn seed or sorghum seed!
To be fair to my younger self, there are a lot of similarities between the corn and sorghum plants when they are in their early stages of growth. However, there are some visible differences that can aid in identification of the young plant.
Sorghum plants tend to tiller much more than corn and will be visible usually within a couple of weeks of emergence. Look for one or two tillers that originate from stacked nodes below the soil surface.
When comparing the two crops, the leaf margins or edges are different. Corn will have smooth leaf margins while sorghum leaf margins are serrated and, under magnification, will look like a fine toothed saw blade. Someone with good eyesight, and maybe a little imagination, can see the serrations. For me, I have to use a magnifying glass. However, these serrations can easily be felt by dragging a fingertip along the leaf margin. A sorghum leaf margin will feel rough and tend to grab at your fingertip, while a corn leaf margin is smooth. This is one of the best ways to tell the two plants apart.
Simply observing the plant population, or space between the plants in the row, can be the first clue as to which crop has been planted. Sorghum is typically seeded at a much higher population than corn. On 30 inch rows, sorghum plants may be as close as three inches apart, but seldom wider than 10 inches depending on the anticipated moisture conditions of the field. Corn, however, will seldom be closer than six inches apart and could be as wide as 14 inches between plants under extreme dryland conditions. The spacing between plants also tends to be more uniform with corn compared to sorghum.
As the plants get a little bigger, the corn leaves tend to be more upright, or set at a more narrow angle when coming off of the stalk than sorghum. In addition, the leaves tend to be further apart on corn, although this is not very apparent early in the season.
Hopefully, these tips will be helpful to young agronomists and crop consultants to distinguish between sorghum and corn plants quickly. If not, like me, you can always dig up the plant and observe the seed.