Farm and Field

Hot, dry weather spells trouble for Missouri corn, soybean

Posted: Jun. 10, 2018 12:01 am

Missouri's record-breaking May heat and lack of precipitation set the stage for two unusual conditions in the state's top cash crops -- corn and soybean.

University of Missouri Extension agronomist Bill Wiebold urges farmers to look for rootless corn syndrome and heat canker in soybean, conditions that result from drought and heat effects on seedlings and young plants.

Corn plants produce two root systems. The first consists of roots that emerge from the seed and nourish the seedling. The second contains adventitious (nodal) roots that form at stem nodes below and above the soil surface.

"This is the main root system of the corn plant," Wiebold said. "Plant health and yield is closely tied to the health and function of these roots."

Corn nodal roots form near the soil surface and depend highly on soil moisture there. In most years, precipitation keeps the soil wet enough for roots to grow, but early-season drought can dry soil to a point where roots cannot grow. Root growth is inhibited and even prevented by dry soil, and a syndrome called rootless corn may occur.

Affected seedlings grow normal primary roots but lack adventitious roots. "These plants may appear normal but begin to lodge when plants are about 15 inches tall because they are weakly anchored," Wiebold said.

Most Missouri corn is well beyond any concern, but late-planted corn, including replanted fields, may be vulnerable to rootless corn syndrome if the soil surface is unusually dry.

Heat canker in soybean also ties to soil surface temperature.

Emerging soybean seedlings up to V2 are vulnerable to heat canker. Young cells in the region where the hypocotyl touches the soil surface cannot tolerate high temperatures and die.

"Hundreds of thousands of Missouri soybean acres have been planted during dry, hot weather," Wiebold said. "Heat canker could be more widespread and affect a larger portion of seedlings than usual."

No-till fields have an advantage. It is rare to see heat canker in no-till fields because previous crop residue that remains on the soil surface reduces water evaporation and slows the rise in soil temperature.


Short grass

Hot, dry weather with short grass growth slowed bidders at the spring sale of Show-Me-Select replacement heifers, held June 2 in Palmyra.

The 134 calving-ease bred heifers averaged $1,598 in the final of four spring sales in the state.

"Many farmers have depleted hay supplies. Short rainfall set the tone," said Daniel Mallory, coordinator and regional University of Missouri Extension specialist based in New London.

Top average price per consignor was $1,723 to MU Greenley Center, Novelty. The center's top price was $1,800.

While bidders were slow, they will be pleased with calf prices next spring. "Those fall calves next spring might bring what buyers paid for these heifers," said Zac Erwin, MU Extension specialist in Kirksville.

It's not the market but the feed supply that reflects bidder worries. "Low hay supply, low hay yield and little rain doesn't make anyone excited to own anything bred right now," Erwin said.


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