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Corn+Soybean Digest

Planting Corn Late Can Cause Big Yield Loss

“Planting corn late can get you into a lot more trouble than planting early.” That’s the opinion of Paul Jasa, University of Nebraska agricultural engineer and no-till specialist who is a firm believer in getting corn in the ground ASAP. “The penalty for planting one week early is usually a lot less than planting late,” says Jasa, whose regimen of no-till production at the university’s research farm east of Lincoln paints a picture of what growers can expect from their crops under various conditions.

New hybrids on the market enable growers to plant corn earlier, in cooler conditions, he says. They can help growers offset problems from weeds, not enough growing days and further hurdles if harvest is delayed – all potential problems associated with late planting. Better seed treatments and traits can also protect corn against seedling diseases and early insect problems.

Different parts of the country suffered through delayed planting in 2009. Some were three weeks to a month late. Others stretched to about June 1. “We were fortunate,” says Jasa, “because we have so much no-till production, we got about 80% of our corn planted on time. Those without no-till were still waiting for the soil to dry up enough to till, then plant.”

Ideally, growers over much of the Corn Belt see late April as a perfect time to plant corn. “Here in eastern Nebraska, it’s about April 25,” says Jasa. “You should try to have two-thirds of your crop planted by that date to reduce problems if finishing planting is delayed.”

Peter Thomison, Ohio State University Extension agronomist, adds that having to delay planting into June is where growers get into trouble.

“It’s when corn planting drags into June that the crop could be subjected to problems later in the season,” says Thomison, who saw many Ohio growers struggling to plant well into May in 2008 and 2009. “Late-planted corn is more sensitive to drought stress, more vulnerable to stalk quality issues and more prone to disease and insect problems.”

Reduced yields can often be seen once planting is delayed past mid-May, says Jasa. “Research indicates that you’ll typically start seeing yield losses on corn planted after May 15,” he says. “It can go down 1% for every day after that.”

He points out that one particular field in northeast Nebraska was severely hampered by lateness in 2009. “It was planted 10 days late,” he says. “With that pressure and the pressure from standability problems and a later harvest due to fall rains, yields dropped by one-third.”

Jasa stresses that getting corn planted late deprives the plant from one of its major ingredients for producing high yields: sunlight. “We try to harvest as much sunlight and carbon dioxide as possible,” he says, adding that even shorter-season hybrids can’t handle the late-season stress caused by the lack of sufficient sunlight.

Late-planted corn also misses out on the full advantages provided by spring rains.

“Corn planted in April usually goes into soil that has a complete soil profile,” says Jasa. “It’s already growing and can take advantage of soaking rains that normally come in later April and May.

“But if corn is planted well into May, when the soil profile is already full, rains are not absorbed by the soil or used by the plant,” he says.

Weed pressure can hit late-planted corn from different angles. Jasa points out that weeds can get a jump on late-planted corn, particularly in no-till.

“A lot of growers don’t think about weeds as a problem for late-planted corn,” he says. “But when weeds are a foot tall in May, that’s a big problem for young corn plants. Also, weeds are not uniform, so they can be more difficult to control.”

Thomison says poor growing conditions can hurt late-planted corn. “Many times late-planted corn is associated with lower yields because the crop is subjected to less favorable growing conditions, such as high temperatures and less moisture during grain fill,” he says.

“This puts more stress on the crop and hurts yield potential. Much of what impacts the crop has more to do with what corn experiences later in the season than conditions at the time of planting.”

Jasa discounts old-school thoughts that early planting hurts yields. “Some say that if you plant too early, the plant grows more slowly,” he says. “Well, I think that slower top growth enables photosynthesis to go to root growth. It helps you develop a better root system.

“Later-planted corn may come up quicker, but it can become taller and skinnier. Plants can be 10-12 ft. tall and see issues with sturdiness,” he says.

Corn planted late will usually mature late and face cool temperatures and potential wet fall weather, says Jasa. “Also, the test weight can be lower if frost hits because of the delayed maturity,” he says. “Some say early season corn will offset late planting, but 90-day corn may not be able to handle heat stress like 110-day corn. Yet, a trade-off as harvest may not be delayed.”

Thomison says growers who are steadily concerned about drying down corn may look at shorter-season hybrids. “One argument for switching to shorter-season hybrids is concern about drying down corn,” he says. “Shorter-season hybrids can help reduce drying costs. However, for the most part, growers are better off sticking with the hybrids they have now.”

Jasa suggests that growers consider planting deeper as well as getting the crop in early. “I like to plant deeper, 2½-3 in. deep, compared to 1½-2 in. that many growers go by,” he explains. “It helps prevent damage from a late-spring frost and you can also get a more uniform stand.”

Spreading out planting among corn and soybeans can help growers get their corn in sooner. “Growers could plant a few of their soybean acres in early April before starting their corn panting,” says Jasa. “That can help you get the corn in without having to worry about all of your soybeans being planted late after corn.”

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