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Soil Crusting Could Lead to Floppy Corn

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Written Tuesday, May 19, 1998  

For the vast majority of corn growers in Indiana and Ohio, the recent warm, sunny days have been a wished-for gift. For some, however, the transition from too wet to very warm and dry, means their seedlings may be struggling.

The weather change has caused a substantial crust to form in fields that were worked and planted in late April, according to Purdue Extension agronomist Bob Nielsen.

"A thick crust can restrict the emergence of corn and cause underground leafing," he says. "The rapid drying of the upper soil layer also is conducive for the development of floppy corn syndrome."

Nielsen says root buds that begin to elongate in dry soil or in soil cracks may quickly stop growing if they don't have enough soil moisture and root tips may die. "If the soil remains dry long enough, the whole root bud may die. At this point, the plant's survival depends on improved soil moisture conditions and the development of the next set of nodal roots," he says.

If the soil surface stays dry and/or the weather remains hot and dry, Nielsen says several sets of nodal roots may fail to form. That would give rise to "rootless corn." These corn plants have to depend on the seminal roots and mesocotyl for nourishment, when normally their function would've become secondary to the nodal root system.

Aside from nutrient stress that inadequate nodal root systems can cause, there is the chance for floppy corn. "Plants simply flop over at the soil surface at the slightest nudge from wind, tire traffic or even crop scouts walking down the row," Nielsen says. "These plants technically are not root-lodged, they are simply broken over at the base of the stem near the crown. The nodal roots will appear stubbed off but not eaten. The root tips will be dry and shriveled."

What distinguishes this damage from herbicide injury or insect feeding is that several sets of roots simply may not have formed below ground, and the crown may appear to be at or above the surface.

"The important thing to remember is that roots do not grow toward moisture on purpose," Nielsen says. "If the root tips of very young roots die before soil moisture is encountered, root elongation will simply cease. If roots are already in moist soil, however, they may proliferate rapidly enough to follow moisture down as the soil dries.

"Row cultivation may encourage root development if moist soil is thrown around the bases of the plants. The ultimate solution to the problem is a good soaking rain."


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