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corn roots Tom J. Bechman
DEPTH QUESTION: Does planting depth shift rooting depth? It’s not a trick question, but Bob Nielsen with Purdue Extension says if you overthink it, you will miss it. As long as seed is planted an inch deep, the answer is no.

Corn roots: Separate fact from fiction

Corn Illustrated: Learn more about the roots responsible for producing top corn yields.

Is everything you know about corn roots fact?

Bob Nielsen, Purdue University Extension corn specialist, says beliefs you have about corn roots may not be as clear cut as you think. Nielsen explains corn root development in this article.

Here are some statements about corn roots and how they develop. Read on to find out whether they’re fact or myth.

Plant deeper, root deeper. This is mostly myth, with a slight hint of truth, Nielsen says. The true part is that seminal roots, the first roots that emerge, will be influenced by seeding depth. However, he notes that the most important roots are nodal roots, which develop next. Nodal roots develop from the crown of the plant. Therefore, nodal root depth is not influenced much at all by seedling depth, Nielsen says.

Deeper seed placement means a deeper crown. Not true, Nielsen says. The depth at which the emerging seedling senses changes in red to far-red light within the light spectrum determines crown location. If you plant 1 inch or deeper, that point will be about a half inch to three-fourths inch below the surface. So, the crown, which is the base of the emerging coleoptile, will be consistently about one-half to three-fourths inch deep, even if you plant seeds 3 inches deep or deeper.

Brace roots provide no benefit other than stalk support. Wrong again, Nielsen says. Brace roots are simply nodal roots that form at or above ground level. They function identically to roots that form below ground, Nielsen says. If surface soil conditions are favorable and it’s not excessively hot, brace roots will penetrate the soil. Once they do and if conditions remain favorable, they can proliferate and effectively scavenge upper soil layers for water and nutrients.

Typical root hairs only live about two days. That is fact, Nielsen says. But in those two days, they can accomplish a lot for the plant. Then they’re replaced by more root hairs. You can even find them on the radicle root, which emerges from the seed first, Nielsen says. Collectively, as the plant develops, the surface area represented by root hairs is very large. They account for a large share of nutrient and moisture uptake by corn plants.

If it’s hot, root hairs may not even live two days. Their lifespan is somewhat governed by soil temperature.

Starter fertilizer benefits kick in at the V3 stage. This is another fact, Nielsen says. Plants typically transition from nourishment by the kernel reserves, fed by seminal roots, to nourishment by nodal roots. If conditions are good, the transition is smooth. However, if growing conditions are poor and nodal root development is subpar due to weather, soil compaction or other factors, it may be a rocky transition.

Starter fertilizer can aid in the transition, especially if placed 2 inches to the side and 2 inches below the seed, where nodal roots can find it.

Nielsen adds a note of caution, however. Even though starter fertilizer helps corn look better, he and Jim Camberato, another Purdue Extension agronomist, don’t consistently find a yield increase with use of starter fertilizer. Sometimes it provides a yield boost; sometimes it doesn’t. However, it almost always results in lower grain moisture at harvest.

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