Iowa Farmer Today
12-30-06
Southwest Iowa field planted to corn for nearly 60 years
By Tim Hoskins, Iowa Farmer Today
As farmers make plans for their crops next year, many are thinking about
increasing their corn acres. That means some ground will be planted to secondyear corn.
However, one Iowa farmer’s family has been planting continuous corn in the
same 11-acre field for nearly 60 years.
Mervin Walter of Prescott may have one of the longest continuous corn fields in
the country.
Some other long-term continuous corn plots are at universities for research. At
the Iowa State University research farm in Ames, one plot had had continuous
corn on it since 1915. That continuous corn plot ended this past year.
Some of the older continuous corn plots in the country include the Knorr-Holden
plot in western Nebraska that was established in 1912 and Morrow Plots on the
campus of the University of Illinois.
The Morrow plots claim to be the longest continuous corn plots in the world.
While Walter’s 11 acres are close to being planted to corn for 60 years, another
four acres of the Southwest Iowa field has grown corn for 40 years.
While there is a lot of talk about more acres being planted to corn next year,
Roger Elmore, Iowa State University Extension corn specialist, says the
situation is like going back to the future.
In the 1950s and 1960s, it was common for farmers to plant continuous corn to
feed livestock on their farms.
While he has grown continuous corn for a number of years, Walter says the
continuous field only out-yielded his corn-soybean rotation one time.
That was a couple years ago, when his continuous field yielded more than 200
bu./acre.
“Your yields (for continuous corn) don’t rebound to first-year corn levels,” Elmore
says.
Generally, second-year and continuous corn will yield less than corn rotated with
soybeans, he notes.
A review of published studies suggest an average 9 percent yield is lost between
continuous and corn planted as part of a rotation. The range was from 2 to 23
percent.
In Iowa, some studies have shown yield loss ranged from 2-28 percent.
Rootworm damage is one immediate concern with multiple years of corn.
Walter says only the second year of continuous corn is the one to worry about
with rootworms.
“It is the second year that they really hit it,” he says.
However, the Adams County farmer now uses Bt hybrids with traits to control
rootworm and corn borers. In the past, he sprayed insecticides to control the
pests.
Walter says the improved genetics in corn hybrids have proven themselves,
particularly this past year.
This past year, he says his area only saw 51⁄2 inches of rain over three months.
“We were dry.”
When he checked yields, the field produced 131 bu./acre. If he had used older
genetics, Walter says the field would have been lucky to have yielded 75 bu.
Elmore says farmers thinking of planting continuous corn should spend time
selecting the correct hybrid.
Farmers should pay attention to defensive traits for disease resistance and insect
resistance when selecting a hybrid, he advises.
Elmore recommends hybrids be rotated in the continuous field. Selecting
different hybrids could help reduce or prevent the build up of disease inoculum in
the soil.
From a long-term agronomic point of view, Elmore says farmers should look at
changing the herbicide mode of action if planting a herbicide-resistant hybrid.
While continuous corn yields will not match that of first-year corn, input costs
could go up, also.
Walter says he uses more nitrogen and lime on his continuous corn field.
Elmore says ISU research by John Sawyer, a soil fertility specialist, found
continuous corn takes about 60 pounds more nitrogen than first-year corn.
Instead of applying lime every six years to the continuous corn field, Walter
applies lime every three years.
In addition, Elmore says farmers should pay attention to their phosphorus levels
when planting continuous corn.
Farmers should consider a few more things when thinking about planting
continuous corn, he notes.
One item is equipment size. With corn and soybeans, Elmore says the planting
and harvesting window is longer.
However, there is a shorter planting and harvesting window when moving to one
crop.
The problem can be solved by the either lengthening the window by planting
and/or combining earlier or later. It also can be solved by using larger equipment
that would cover more acres in the same time.
Another consideration should be crop diseases or pests in other crops. One
suggestion was to plant ground with high soybean cyst nematode (SCN)
populations to second-year corn to help control SCN.
However, Elmore says research shows nematodes can live for many years in the
soil, so planting two years of corn will not rid a field of SCN problems.
While, for most farmers, the decision to plant continuous corn is based on prices,
Walter just wants to keep the continuous field going.
He rents out the continuous corn field. However, he says it is written in the lease
corn will be planted in that field.
“I am trying to keep it continuous corn,” he says. “It is a stubborn streak, I guess.
I hope someone will keep it in corn.”