Last week's cool, wet weather statewide kept farmers from doing any fieldwork. Farmers are anxious about the soggy spring and the delay for the start of corn planting.
If you like to get started planting by April 15 to 20, is that the ideal date? Not if soil conditions are too wet and too cold to plant. There's still time to plant corn without losing yield potential, says Iowa State University Extension corn agronomist Roger Elmore.
"In Iowa, historically, we've never had more than 6% of the state's corn planted by April 15," he notes. "Normally, we run 0% to 3% of the corn acreage planted at that point. In 2005, we had 6% planted by April 15." He adds, "If you look at corn yield responses in our ISU studies, planting early doesn't really increase yields compared to planting a few weeks later. In fact, we can go until about May 10 before we start reducing yield potential on corn in Iowa."
Corn rooting problems hurt yield
"Don't mud it in," says Elmore. "The worst case is to plant a lot of acres when it's cold and wet. You'll end up with rooting problems on those seedlings; poor root distribution, rootless corn, sidewall compaction, etc. That results in more plant-to-plant variability. Plant-to-plant variability reduces yield potential."
Watch the weather forecast if you are looking at planting early. Another possible situation you want to avoid is planting corn in warm conditions if you know the weather is going to turn cold within a week. Elmore says that's worse than planting when it is slightly cold and you know the weather is going to warm up within a week.
"In other words, the soil temperature at planting depth has to be on a positive upward trend to get the corn really up and growing well," notes Elmore.
Take a cue from corn yield contest winners and what they do to get their corn up and off to a fast start. "They do all the little things it takes to get a good uniform stand of corn," notes Elmore. "One thing that seems to be consistent with getting high corn yields, and I'm convinced of this when I walk fields and look at the stands each year, is that every plant needs to look like every plant. Good uniformity of stands is what you need."
Need uniformity of growth stages
It is important that the corn plants in a field are uniform in terms of growth stages. They should all be in the three-leaf stage, for example. Or they are all at 10th leaf stage simultaneously.
"If the growth stages aren't uniform, the plant that is behind ends up acting like a weed, using moisture and nutrients and competing with the other corn plants," he explains. "If you have a two-leaf difference in half the plants out there, for example, that's about a 6% yield loss. With today's high corn yields and high prices, 6% is a big number."
Farmers can't control Mother Nature but they can control their planting management. That means farmers should be looking at the right timing for planting and being ready to plant when soils are warming up and conditions are improving.
"If you had a perfect week to plant corn in terms of timing, and if soil conditions are favorable, it would be the last week of April," observes Elmore. "Of course if you have a lot of acres to plant, you have to start planting earlier and you'll likely have to go later than the last week of April, but the main point is, you don't want to mud the crop in. A good goal in Iowa is to try to finish corn planting by May 10."