June 02, 2016 5:11 am •
NASHUA — Repeated bouts of cold weather slowed corn and soybean growth across Iowa.
In northern Iowa, frost injury was present, while excess moisture in the Prairie Pothole region led to replanting some fields.
Sunny skies warmed rows of young corn and soybeans at the Northeast Research and Demonstration Farm west of Nashua as Farm Superintendent Ken Pecinovsky and Extension Field Agronomist Brian Lang walked the test plots May 19.
Most corn plots were in V1 to V2 stage development, and a yellow tint was evident from many days of cool temperatures. Some plants had a frosted leaf or two.
Pecinovsky recalled clear skies during the night of May 14-15. On May 15, a morning air temperature of 29.3 degrees was recorded at the research station, he said.
The 4-inch ground temps fell to 44 degrees that night but reached 60 degrees the following afternoon, Lang said.
“So it didn’t stay cold very long,” he said. “28 degrees is considered a killing frost.”
He explained the corn’s growing point was still below ground, making a yield reduction from lower plant population unlikely.
“I don’t know of anybody needing to replant corn” because of the frost, he said.
Lang had just returned from Lime Springs in far Northeast Iowa, where he saw a soybean field that would need to be replanted due to frost damage.
Even in cases where the beans were killed, it was not uniform. Several factors, including planting date, landform type, soil texture and surface residue, affect susceptibility to frost, he said.
Lang said this frost event should not be cause for caution in the future regarding early planting. Iowa’s crop planting progress was ahead of the five-year average this spring, but it was well within the recommended planting dates for optimum yields, he said.
“Many mid-Aprils the soil is still too cold,” Lang said.
But if you have good planting conditions, there’s nothing wrong with starting early, he said.
Mark Licht, Iowa State Extension cropping systems agronomist, said May 18 cold temperatures were the predominant issues for corn and soybeans fields across the state.
“Obviously, some places are better than others. Generally, the corn crop is still pretty yellow,” Licht said.
After checking fields earlier that day with new crop scouts at Iowa State’s Scout School, Licht said, “We have plenty of soil moisture at a half inch down.”
Now is a great time for beginners and old pros alike to get out and check their fields, Licht said.
By scouting now, growers can establish a baseline of what a stand looks like going into the season and estimate planting rate vs. population, he said.
This will help later in the growing season with knowing where to look for problems and next spring when calibrating planters, he explained.
For the northern portion of Iowa, farmers may want to check to see if things are alive and growing well after the light frost, Licht said.
He described a pattern of warm weather windows when planting occurred, followed by cooler temperatures.
“The vigor and growth of the corn crop is really quite slow,” he said.
Forecasts for a warm weekend May 21-22 would likely “help that crop along quite a bit,” Licht said.
He said emergence issues, like imbibitional chilling injury, likely affected less than 1 percent of the crop.
He had also heard reports of black cutworms but nothing yet that would reach a treatment threshold.
The May 15 frost event hit “largely the northern two tiers of Iowa in the North Central and Northeast,” Licht said.
While this event was cause for concern, Licht said most of the corn statewide appeared to have weathered the frost okay.
He said significant rains in the Prairie Pothole Region of Iowa were causing corn replanting, but statewide this accounted for a small percentage of fields.
“We just need some warm weather to pull us through,” Licht said. “I think it’s more temperature related than anything — temps below 50, corn and soybeans just don’t grow.”
Source: Iowa Farmer Today