In spite of March weather that's on track to be the warmest ever in Iowa history, don't expect to see corn emerging from the sun-drenched soil in northwest and north central Iowa anytime soon.
Why not, one might ask, when Iowans have seen daytime highs in 70s and even 80s multiple times this past month?
The answer: It's simply too great a risk because there's too much history on the side of freezing temperatures breaking through sometime yet this month or early in April.
"In northwest Iowa, there's still potential for frost, even in mid-April," said Joel DeJong, a crop field agronomist for Iowa State University Extension in northwest Iowa. "I can remember years of getting snow on top of planted corn ... It's expensive to replant."
Another major consideration for growers is the date crop insurers establish as the earliest planting date; if growers plant prior to that date they would not be eligible for crop insurance for that field.
DeJong doubts he'll see any farmers planting until around April 10.
He does, however, expect farmers to get all of the pre-planting activity like spreading manure, applying nitrogen and tillage work completed early.
Normally, growers in the far northwest corner wait until April 15 or even April 20, but this year could be an exception.
"If it stays this nice, we'll see some planting," DeJong said.
Aside from the frost concerns, DeJong said the pest and weed risks are about the same with early planting as they would be with normal planting dates.
"There are a lot of fields where weeds are starting to grow. From that perspective, if you get most of them growing early and make a tillage pass or apply your weed control, it's more effective." DeJong said.
On the insect side, DeJong said there are some pests that will be present more quickly this year because of the mild winter.
"But they might run out of food before the crop has emerged. They might starve to death before they get a food source to feed on," he said.
Other major pests are basically unaffected by the mild winter. Corn rootworm overwinters in the soil, so above-ground temperatures have little impact.
"Black cutworms never overwinter in Iowa. They fly up from the south in spring, so a nice winter doesn't impact them," DeJong said.
One pest that could be more prevalent is the European corn borer. "They could have higher survivability," DeJong said.
He doesn't expect the corn borer to make a big impact on yields, however, since many varieties of corn seed include Bt traits resistant to that pest.
In years past, an unseasonably warm winter might have caused major pest problems for growers, DeJong said, but most farmers have sophisticated pest management plans in place now.
Studies in the 1980s in Iowa indicated that on average, the best time to plant corn was from April 20 to May 10, according to an Iowa State University Extension release.
More recent studies indicate that the optimum time for planting corn in Iowa still falls between April 20 and May 5.
However, numerous factors influence the decision of when to start planting corn, according to the Extension release.
How early one needs to begin planting corn in order to be completed by mid-May depends on soil conditions, acres planted per day, work days available and total number of acres to be planted.
During late April and early May, only about half the days normally are suited for field work.
Contact Dave DeValois at email@example.com.