Most people who walk cornfields this year are looking at one of two things. Either they’re concerned about foliar diseases, looking for lesions and deciding if fungicide applications worked, or they’re looking at the business part of the plant — the ears — and estimating yield. Dave Nanda believes they also ought to look down and pay attention to ground level. What type of root system is supporting each stalk?
If ears are the business end of the corn plant, roots are the foundation of the factory that makes production of grain possible, says Nanda, director of genetics for Seed Genetics Direct. This company, based near Jeffersonville, Ohio, sponsors Corn Watch ’20.
Many things affect how roots develop, Nanda says, including plant genetics, weather patterns, and presence or absence of soil compaction. Here are a few things to look for as you examine roots this season:
Root strength. If stalks are going to stand until harvest, roots must be strong enough to support them. An effective root system establishes itself by spreading out, since corn has a fibrous root system, but also by sending roots deep into the soil. That helps pull up moisture and nutrients from deeper in the soil, and is vital if it turns dry, Nanda says.
Standability. Early in the season, if it’s very dry when roots are establishing themselves or if there is soil compaction just below the surface, roots may be shallow. In fact, if plants are in the early vegetative stages and root development is too minimal, you may get “floppy corn syndrome,” illustrated in the lead photo for this story. Bob Nielsen, Purdue University Extension corn specialist, coined the phrase years ago to explain why young plants with shallow roots tended to fall over, especially in a storm.
Brace roots. The picture below shows some plants without strong brace roots above the soil. Brace roots help anchor plants. If it’s too wet or too dry, plants may not develop nodal brace roots that are strong enough to support them.
Tom J. Bechman
NEED MORE BRACE ROOTS: This corn has minimal brace roots, possibly influenced by soil compaction and a wet spell. Some plants affected by wind goosenecked but still stayed upright.
Root mass. Digging a couple of plants and getting as much of the root mass as you can isn’t an easy task, but it is a good way to compare root systems between hybrids, Nanda says. Most county fairs didn’t have open exhibits that visitors could observe this year. But in most years, if you check the county crops exhibit where 4-H members dig up two or three stalks of corn, you will likely find big differences in root mass. Proliferation of root hairs adds to the mass. Root hairs are important to pull moisture and nutrients into the plant.
Flat roots. If you dig up a few plants or see plants on exhibit and the roots appear to run horizontally, or flat, a few inches below the surface before turning downward, it’s likely they hit a horizontal soil compaction layer, Nanda says. How much that affects final yield may depend on whether you had ample moisture at key times to offset effects of limited rooting related to soil compaction.