'Flash drought' hurts young corn plants

COLUMBIA, Mo. – “Call it a flash drought,” said Pat Guinan, University of Missouri climatologist. The fast developing drought slows growing crops.

No rain and high temperatures cover most of Missouri and nearby regions. Abnormally dry weather covers much of the mid-western Corn Belt.

Soil moisture reserves are drawn down by high evapotranspiration rates. That's a combination of solar radiation, temperatures, relative humidity and wind to evaporate water from soil and plants.

“Those combined with many cloudless days in May to hasten loss of soil moisture,” Guinan said.

May, usually the wettest month of the year and when corn really begins to grow, is on track to be abnormally dry. “According to weather records, the Missouri Bootheel has one of the driest April-May periods in 118 years,” Guinan said.

Those unusually dry conditions affected only the Bootheel in early spring, but cover the entire state as Memorial Day weekend approaches.

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

The drought already causes death of corn roots, Bill Wiebold, MU agronomist, told regional extension specialists on a weekly teleconference.

“This may be a year with rootless corn,” Wiebold said. A set of roots extending from the first node of the corn stalk will dry up and die if they do not find moisture.

Those nodal roots, sometimes called brace roots, supply needed moisture for cornstalk growth. Some corn plants in MU research plots are just seven inches tall. “Usually corn would be knee-high by now,” Wiebold said. “While they are called brace roots, the nodal roots supply moisture for the growing plant. Without water, the plant cells don't elongate.”

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

Corn plants might overcome the initial lack of root growth, if rain falls soon. “The corn plant keeps trying to put out new roots,” Wiebold said.

Until those nodal roots form, the plant depends on primary roots, which 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 fall over from lack of support.