Frosty temps on the way to the Corn Belt
A freeze warning is in effect for parts of the Corn Belt through this weekend, and if the forecasted temperatures in the 30s are realized, it could mean trouble for still-green soybeans in the region.
Frost advisories blanket the weather forecast for this weekend in much of the northern region of the nation's midsection, according to Freese-Notis Weather, Inc. Friday morning's Freese-Notis forecast calls for frost and freeze warnings in parts of South Dakota, Iowa, Minnesota, Wisconsin, Illinois and Missouri.
"One can assume correctly that the cold Saturday morning that we have long been expecting is still very much on track to occur," according to Freese-Notis on Friday. "We should find several locations [in the central and northern Corn Belt] with low temperatures down to 27 to 28 degrees, so it looks like we are going to see a legitimate 'freeze' tonight for some locales."
Temperatures will likely sink the most in Iowa, north of Highway 30, which bisects the state in central Iowa, according to QT Weather meteorologist Allan Motew. This will likely amount to record lows that comprise z "once-in-25-years" weather event.
"The most damage will occur Saturday morning across northern Iowa and southwestern Wisconsin," Motew said Friday morning. "This means 10% of Iowa's prime acreage and 14% of Illinois' is in the center of harm's way for damage. This does not include the millions of acres elsewhere in Minnesota, Wisconsin, Iowa and Illinois, which will experience record frost and some damage."
What will this mean to the corn and soybean crops in the region? Severe damage requires other conditions in most cases, Motew says, but moderate damage can occur with the temperatures forecast alone.
"A frost of 30 degrees (Fahrenheit) or lower will cause damage to stems and green pods. Beans in the upper part of the plant that are still green and soft will shrivel. Upper stems will rapidly turn dark green to brown and will not recover. Soybeans in lower pods that are filling should mature normally. Some of the uppermost pods may abort after the frost. Top yields, however, can be lost in most damaged fields. Some delays in maturity may occur," Motew said. "Corn usually is severely damaged by temperatures at 29 degrees or lower. Colder temperatures will kill the entire stalk. If only leaves above the ear are frosted by temperatures of 30 to 32 degrees, which is a light frost, then kernel development will continue. If the entire stalk, ear shank and leaves are frozen, kernel development will cease and soft, shriveled corn will result."
Other conditions, including wind speeds and the duration of the freezing temperatures, will often dictate the amount of damage freezing temperatures will do to maturing crops.
"Usually a two- to four-hour duration of a critical low temperature will cause damage," Motew says. "Two other factors that influence critical frost temperatures are soil moisture and wind velocity. When soil moisture is higher, frost injury is somewhat reduced due to heat slowly being released from the stored heat in the soil within a plant canopy."