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When it comes to posting the highest average corn yields in the state, several Northwest Iowa counties are often near the top of the list, but the title tends to move around the state depending on growing season weather.
In 2015, Cherokee County led the state with an average 209.6 bushels per acre. Pocahontas County was second with 205.5 and also placed fifth in 2012 with 165.3 after dry conditions lowered yields statewide.
But O’Brien County, taking third in 2015 with 205.2, has maintained the highest average yields over the past decade, putting up a 10-year average yield of 184 bushels per acre, according to the USDA National Agricultural Statistics Service’s Iowa Office.
On the soybean side, Sioux County is on top with a 10-year average of 57 bushels per acre — leading the state for highest soybean yield averages for the past three years in a row. In 2015, Sioux County’s average soybean yield was 64.1 bushels per acre.
Joel DeJong, Iowa State Extension agronomist for Cherokee, Lyon, O’Brien, Osceola, Plymouth, Sioux and Woodbury counties, said several factors contribute to the region’s big yields.
“We’ve got a lot of deep loess soils that hold a lot of water and yet, internally, are very well drained,” DeJong said.
Historically, Northwest Iowa was among the driest parts of the state, but the amount of average annual rainfall has increased in recent years, he said.
Very timely planting is also a local advantage in many years.
“We haven’t had excess water in many years,” DeJong said.
John Schott, who farms in Pocahontas County, echoed DeJong’s appraisal.
“The first thing is we’ve got good deep soils that can take us through the stressful times of the year,” Schott said.
He said farmers in his area have also taken advantage of grid sampling and use variable rate fertility programs.
“I think that pays off in the long run,” Schott said.
But even in good, deep soils, crop variety selection is still important, he said.
“The last couple of years. The later the variety of corn, the better it yields. That’ll change from year to year,” Schott said.
Schott agreed that more rainfall, especially in the critical July/August period, has also made a difference for corn yields.
DeJong said many Northwest Iowa soils don’t have a restrictive layer stopping downward root movement.
“We’ve done lots of root pits and found corn roots 7, 8, 9 feet deep. Five foot (deep) is normal for Iowa,” DeJong said. “We have a lot of livestock production here, which means we utilize manure a lot. Some data says that can be a benefit.”
Compared to Southeast Iowa, Northwest Iowa also seems to have less disease pressure in many years, DeJong said.
Schott said disease pressure is something growers watch closely. He said some corn varieties may respond better to fungicide treatments.
As for his approach to high yields, Schott said it’s the same all across Iowa.
“I have friends from Southeast Iowa to Northwest Iowa, everybody is striving to do the same thing — make sure the costs you put on the land are going to give you a return,” he said.
“With the inputs that we have and tight margins, you are definitely trying to do as many things right as you can. Every year is different, and you have a lot of different factors that go in to making a good year.”
The cheapest seed might do well one year, but may end up costing you another year, he explained.
Schott expected Pocahontas County to have “very, very good” yield averages again this year.
DeJong said O’Brien County had some planting delays last spring and areas to the west with better drainage might claim the top spot this year.
“We’re fortunate to be farming the soils we are farming. We need to take care of them to keep them,” DeJong said. “The soils still are very productive. They are some of the youngest soils in the state.”
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