Heavy rains over much of the state have headed off a developing problem of what University of Missouri agronomists call "rootless corn syndrome."

Much of the corn was planted into fields that were worked too wet as continuous rains delayed planting this spring. Corn planted in those conditions tends to have difficulty establishing strong secondary roots needed to hold the plants erect, said Bill Wiebold, MU extension crops specialist. Similar conditions in 1999 caused widespread cases of corn falling over.

After rain delays this spring many farmers rushed to plant, often into less-than-ideal seedbeds, Wiebold said. Record-setting heat and dry weather aggravated the problem as the corn was coming up.

Ground worked too wet becomes compacted and cloddy, Wiebold said, providing poor growing conditions for new roots.

Corn has two root systems. The primary roots help the plant emerge and start development. They are thin and grow only about a foot long.

Secondary roots emerge from nodes on the cornstalks. The first node, and the location of the first secondary roots, is about three-fourths of an inch below the soil surface, Wiebold said. These roots start the massive ball of fibrous roots that hold the cornstalk in place.

"Like all roots, these secondary roots require moisture to develop properly," Wiebold said. "Soil that is compacted, too hot, or contains clods is a poor environment for root growth."

When secondary roots fail to develop the corn is likely to begin falling over when it is about four weeks old.

"At some point, the stalk becomes to large to remain upright," Wiebold said. If the toppled plant is pulled up, the secondary roots appear as short stubs. The corn plant appears to be rootless.

Corn that falls over will die if more rainfall doesn't arrive to spur new root development. That can cause crop failure. If rain comes, the downed corn will start growing upward, with part of the corn on the ground. Roots develop from nodes touching the soil. "This is called gooseneck corn and it's a mess to harvest," Wiebold said.

To prevent rootless corn, water is needed to soften the hardened soil so that roots can extend. Few farmers have irrigation equipment to solve the problem. The natural solution is rain.

Rains in the second week of June drenched a large portion of Missouri where the rootless corn syndrome was developing, Wiebold said.

There are areas, particularly in the clay-pan regions of northeast Missouri, where the problem may occur. The problem also may develop in east-central Missouri where corn planting continues because of the rain delays, Wiebold said.

The heavy rains that caused problems for wheat producers brought relief to corn farmers.