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Linda Geist
Senior Information Specialist
University of Missouri Cooperative Media Group

September 25, 2019

Weather challenges still plague Missouri farmers (PART 1/2)

COLUMBIA, Mo. - Most soybean and corn likely will yield less than normal this year due to late planting and unfavorable weather during critical grain-fill periods, says University of Missouri Extension soybean specialist Bill Wiebold.

According to a Sept. 4 USDA Farm Service Agency report, wet and flooded fields kept Missouri farmers from planting 750,000 acres or 21% of corn and 480,000 acres or 9% of soybean.

Farmers planted most intended acres, but after the optimal time. USDA's National Agricultural Statistics Service (NASS) says about 50% of planted corn emerged after May 26. Half of soybean emerged after June 23.

Yield depends largely on weather at certain growth stages-July and August for corn and August and September for soybean. Temperature and rain during grain fill affect yields greatly.

Wiebold recently studied Missouri Mesonet weather data and crops over four months at five Missouri locations to look at 2019 crop potential.

He explains that nighttime temperatures affect yield due to respiration rate. Higher temperatures cause faster respiration and raise the potential for yield loss. High nighttime temperatures respire away sugars needed for yield.

In a nutshell, night temperatures below 65 F are good for yield and above 75 F are bad for yield, he says.

Wiebold found nights during June were unusually cool in much of Missouri. At Novelty and Columbia, temperatures dropped below 65 F more than two-thirds of the nights. Cool nights decreased growing degree day accumulation and slowed corn development in June. "Late-planted corn would have benefited from warmer than normal daily minimum temperatures in June," he says.

NASS reported that 80% of Missouri's corn crop reached silk stage by Aug. 1, about two weeks later than normal. As a result, most corn grain fill occurred in August. Temperatures fell below 65 F most nights and only rose above 75 F occasionally. This should help yields, Wiebold says.

Minimum temperatures during August should help soybean yield also, he says. Due to late planting, more than 50% of Missouri's soybean crop flowered after Aug. 1.

Continue with Part 2 of this story HERE.

Photo available for following caption Photo credit: Source: Missouri Mesonet.

Temperature parameters for four months at five locations within Missouri in 2019.

Source: William Wiebold, 573-882-0621

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