When corn growers attended the recent "Corn University" put on by the Wisconsin Corn Growers Association, they had the chance to see something unusual.
Part of the program involved a visit to a soil pit in a test plot in one section of the University of Wisconsin Arlington Agricultural Research Station.
"When they dug this pit it felt like they were ripping my heart out," said Joe Lauer, the UW's corn specialist as he showed growers how the pit had been dug into a crop rotation experiment that's been going on for decades. "But it turned out to be really cool."
The pit gave growers an unusual chance to see the difference between soils that had been treated differently for generations.
One section of the pit showed the soil profile for a plot that had been conventionally tilled and planted from 1983 through 2013. Another section had been roto-tilled since 1984 to keep weeds down between the test plots.
A third section had been no-till from 1986 through the present and a grass alley also contributed to the soil profile. It has been essentially a grassy lawn for 30 years.
For Lauer this is a favorite part of the research farm, just north of DeForest. It's where agronomists have been doing crop rotation trials since before he was part of the university. (He came on board in 1994.)
The trials started in 1983 and no-till plots were added in 1987. The complicated plots involve numerous treatments for both tillage and no-till each year.
"One data point equals 10 years," Lauer said. "You have to get the entire rotation - five years of corn and five years of soybeans - to get a data point.
"It's kind of like time within time to get these rotations."
The purpose of the trial is to look at the effect of crop rotation over time.
Before soybeans were added to the rotation, it was a continuous corn plot and earlier agronomists tracked the yields of corn as the crop was planted year after year.
The trials have shown that by year three, after the rotation back into corn, that yields are basically at the 30-year continuous corn level, he said.
Lauer said the trial began including genetically engineered crops in 1998.
The seed varieties that are planted in the trial are chosen from the UW's hybrid trials. "Hybrid development is always going on. We manage the trials to produce the highest yields."
The long-term trial has shown that conventional tillage always out-yielded no-till plots. But the differences are becoming smaller. "Last cycle the difference was only three percent."
Corn that follows beans probably doesn't need a lot of tillage but continuous corn plots need a little bit of tillage to overcome the effects of that long-term planting, he noted.
The researchers have found that when they add a third crop to the rotation "it benefits all the crops," said Lauer. Talking to growers at the seminar, he sounded amazed by the longevity of the research trial.
"Thirty years of time, that could be a career for a farmer," he said.
Francisco Arriaga, who has been a soil management specialist with the UW-Madison for about a year, is a native of Puerto Rico where he noted that the soils are really red. "These soils are amazing," he said as he showed corn growers the soil pit at the Arlington farm.
The limestone-sand mixture makes up what is called Plano silt loam, a soil that is very forgiving, he said.
Before he came to Madison, Arriaga worked with the U.S. Department of Agriculture in southeast regions of the United States. "Those guys are farming dirt. These soils here developed under a prairie system for thousands of years."
As agriculture was introduced on the Arlington prairie it brought with it a lot of tillage which introduced air into the soil and began to oxidize the prairie soils. "As that organic matter oxidizes, carbon dioxide leaves the soils."
Using water percolating through the various soil profiles exposed by the pit, Arriaga showed how the no-tilled soil was much softer and the tilled plot had a compaction layer.