Many farmers insist on tilling in the fall, despite evidence it could do more harm than good, according to an Iowa State University soil management expert.

“They’re hurting themselves environmentally and economically,” said Mahdi Al-Kaisi, an associate professor in Iowa State’s Department of Agronomy. “You can present all the data and findings, and explain why there is no legitimate reason to do it and they agree, and then they go out and do it anyway.

“It drives me nuts. But I guess there’s the human element of ‘my father did it and my grandfather did it.’”

Al-Kaisi said he doesn’t encourage any form of tillage because of the damage it can do to the soil. Tilling destroys the residue and cover, leaving the soil vulnerable for an extended period, he explained, adding it puts the soil at risk for erosion and the loss of phosphorous and potassium.

“I tell them, if they don’t need to till, then don’t do it. You can also lose a significant amount of organic matter, which is bad for the soil,” he said.

Fall tillage doesn’t make sense economically either, Al-Kaisi noted. It can take approximately 4.1 gallons of fuel to till an acre, and usually, any yield gains are minimal and probably offset by the cost to till, he said.

“You look at the cost versus the yield and they’re definitely ahead with no-till. Not only is there a cost in fuel, but there’s the cost of equipment, wear and tear on the equipment and your time,” he said.

According to a report from Purdue University, from 2000-09, average yields for corn following soybeans after fall chisel plowing were 204 bushels an acre. Yields following fall moldboard plowing averaged 202 bushels an acre, while yields with untilled ground were 201.

The only time Brent Minett, agronomy coordinator with Beck’s Hybrids of Atlanta, Ind., recommends fall tillage is when there’s a wet fall, as there was in 2009. The wet weather causes soil compaction and even taking into consideration the cost of fuel, fall tillage is worth it during those circumstances, he explained.
Farmers who think fall tillage is beneficial in normal weather conditions might not have done enough research on the cost versus reward, Minett said.

“There’s maintenance, the cost of fuel. I don’t know that they always assign enough expenses to how much it costs to plow. It could cost $30 to $35 an acre, especially if they’re doing deep plowing,” he said.

Even though many agronomists in the private sector and in academia tend to agree on the issue of fall tillage, many farmers still believe in it, he noted: “The subject is a hot one, and probably will be until we switch to no-till or less till.”

Farmers who do fall tillage seem to like how their fields look, said Fabian Fernandez, a soil fertility specialist and assistant professor at the University of Illinois at Urbana-Champaign.

“There’s an aesthetic component to tillage, seeing your field nice and black and tilled,” he noted. “Also, you don’t have to worry about residue, and it’s a lot easier to plant in a clean field.”
Fernandez doesn’t recommend fall tillage in fields that have a potential for erosion, although he said it has benefits in cases of soil compaction.

“During wet falls, some fields become heavily compacted, and you need to go in and try to break some of that,” he added. “In those circumstances, you want to till to shatter the clumps, not just try to turn the soil.”