A “flash drought” over most of Missouri and nearby regions is slowing crop growth and killing corn roots unable to get to needed moisture. So say Pat Guinan, University of Missouri (MU) climatologist, and Bill Wiebold, MU agronomist.

Pastures are growing at half-normal rates, adds Rob Kallenbach, MU forage specialist. The only bright side: some high-quality hay was baled early – mostly due to dry weather.

May, usually the wettest month of the year and when corn really begins to grow, looks to end unusually dry. “According to weather records, the Missouri Bootheel has one of the driest April-May periods in 118 years,” Guinan says. Dry conditions look to cover the entire state as Memorial Day weekend approaches. Solar radiation, temperatures, relative humidity and wind have worked to evaporate water from soil and plants.

“It's going to seem more like the Fourth of July,” says Guinan. Temperatures will climb well into the 90s, with low humidity and drying winds, especially in the southern half of Missouri.

“This may be a year with rootless corn,” Wiebold says. Nodal or brace roots, needed to supply moisture for cornstalk growth, are starting to dry up and die. Corn plants in the MU research plots, normally knee-high by now, are only 7” tall, he adds.

The slow start on growth can affect cornstalks all season. “Corn will be shorter and ears will grow closer to the ground,” Wiebold says. “You'll have to aim your combine snout lower this fall.”

If it rains soon, corn plants may be able to put out new roots. But until those nodal roots form, the plant depends on primary roots that grow deeper in the soil from below the seed corn kernel. If primary roots are in dry soil, the plants may die. If secondary roots fail, the plants may lodge.

Guinan hopes a cold front may bring some rain to northern Missouri within the week. “It would be the perfect antidote.”

Corn yields will be hard to predict, Wiebold adds. “In polling my fellow agronomists, I've had estimates of total loss to something just short of a bumper crop.”