Spring crop planting delayed by cold weather in early April faces more delays by late-April rainfall, says Pat Guinan, University of Missouri (MU) climatologist.

Cool temperatures kept soils from warming and delayed corn planting across much of the state in early April. In Columbia, the first 14 days of April were the tenth coldest for that period in 120 years, says Guinan, a weather specialist with the MU Commercial Agriculture Program. Cool air kept soil temperatures in the 40s, except in the Bootheel.

“We need soil temperatures at least 50° for corn planting,” says Bill Wiebold, MU Extension agronomist. “Warm, moist soils encourage rapid seed germination and plant emergence soon after planting.”

In cool soils, seeds that fail to germinate quickly are subject to rot or insect damage. Spring storms with heavy rains are possible for the last week of April.

“It is an unsettled forecast,” Guinan says. “A Canadian front with below-normal temperatures will meet a moisture-laden air mass from the southeast. The forecast calls for that front to lie from New Mexico through Missouri to Michigan by early in the week of April 27. Heaviest spring storms are forecast over portions of Kansas, Nebraska, Missouri, Iowa and Illinois – a large area of the Corn Belt.”

The front is expected to sag southward into Missouri late Sunday. “Significant rainfall of 2+ in. is possible,” Guinan says.

At Sanborn Field, a research plot on the MU campus, average daily soil temperatures did not reach 50° until April 15. Usually soil temperatures average 50° by April 1, with significant corn planting by April 15.

“Prolonged rainfall adds flood risk to low-lying fields over much of Missouri,” Guinan says. “Streams in much of the Missouri and Mississippi watersheds are running near to above normal. Flood potential exists with added rainfall.”

In addition to cool temperatures, large areas of the central U.S. had near- to above-average rainfall during early April. “Soils are wet from Kansas to Michigan,” Guinan says. “That follows the wettest year on record for Missouri in 2008. We are drought-free.”

For other good news, most of the state has passed the average date of last frost. “Northern tiers of counties and parts of the Ozark plateau have the last frost, usually by the third week of April,” he says. “I wish I could give you more certainty for the rest of the growing season. The long-range outlook from the National Climate Center calls for equal chances of below-normal or above-normal rainfall or temperatures. In other words, just flip a coin.
“We are in a transition period out of La Nina weather. Surface temperatures in the Pacific Ocean at the equator are back to normal, leading to uncertainty about Midwestern weather,” says Guinan.

For more on early planting dates, go to: The Earlier The Better.