November 30, 2022

Variable rainfall impacts corn yields

BOONE, Iowa — Variability is one way to describe the 2022 growing season.

“It’s really the story of variability because it depends on where you’re at and if you were lucky enough to catch some rains,” said Jared Goplen, agronomy manager at Wyffels Hybrids, from the company’s booth at the Farm Progress Show.

“If you caught the rains, your crop looks pretty good,” Goplen said. “There is some tip back in areas where there was warm weather around pollination, but if you have the water, kernels are filling out pretty nicely.”

However, it’s a different story for the crops that did not receive adequate rainfall.

“Silage harvest is starting to kick off in South Dakota and western Iowa, so that tells you it’s been pretty dry in some of those areas,” Goplen said.

Wyffels manages an extensive corn rootworm trapping network.

“The corn rootworm pressure was a little lower than normal,” Goplen said.

“Diseases have also been relatively quiet, but there is some tar spot in a pocket of north-central Iowa,” he said. “For most areas it seems like the disease hasn’t been a huge issue and maybe that’s related to the drier weather.”

As harvest approaches, Goplen encourages farmers to watch fields that have not received adequate rainfall during the season.

“We have some concerns about stalk integrity and the ability for the ears to hang onto the stalks,” he said. “We need to make sure we get out there soon enough if we have late season integrity issues.”

Parts of Iowa and Minnesota were impacted by high wind events in early July.

“There was a little green snap in areas and just recently in western Iowa there was wind that caused some corn to go down in areas that were droughty,” Goplen said. “When it’s dry, the stalk starts to cannibalize itself because it is trying to put everything it can into the grain.”

Although planting was delayed with wet conditions in the spring, Goplen said, a lot of Iowa and Illinois are at or above average for growing degree day accumulation.

“Harvest will be close to normal because some of that hot weather put us back in the normal range,” he said.

If water is short through the rest of the grain fill period, that will speed up maturity.

“I talked to a number of guys from Illinois today and there are areas with significant tip back and other areas there isn’t,” Goplen said.

Some of the yield loss from tip back can be recovered if there is good grain fill weather.

“The ears will fill with larger kernels than normal,” Goplen said. “Obviously, it’s not all the yield potential that was there.”

Farmers should record information about their crops each year, Goplen recommended, especially when there are different weather events.

“Think about how you can use that information,” he said. “Maybe you will change your variable seeding prescription, do something different with fertility or do more grid sampling.”

If farmers think their corn may have stalk issues, Goplen said, they should not be afraid to start harvesting the field early.

A Grain Drying Calculator is available on the Wyffels Hybrids website to help farmers make this decision.

“It puts economics to harvesting earlier because there’s some yield loss as the corn dries in the field,” Goplen said.

“You plug in what the early harvest moisture might be and the calculator factors in research we’ve done over the years on harvest timing,” he said. “It is not quite two bushels per day on average that you lose per point of moisture lost when you let it field dry.”

That reduction in yield is due to shattering losses and losses out the back of the combine.

“Then you put in your grain drying cost and it calculates if there’s a net positive return of drying it in the dryer or in the field,” Goplen said. “More often than not, if you have a grain dryer, it pays to harvest earlier to minimize some of the losses.”

Several other calculators are available on the Wyffels website for farmers to use, including a Growing Degree Unit Calculator, Corn Replant Calculator and Yield Calculator.

Martha Blum

Martha Blum

Field Editor