The presentation was called Tillage Systems and Residue Management, but it could have easily been titled, "Soil Compaction 101."
Richard Cruse, an agronomist and director of the Iowa Water Center, told an audience of 60 farmers on Dec. 6 that they need to follow their WANTS. if they expect to get good plant growth from their row crops.
And creating compatible root zones, Cruse said, will get the job done.
-Messenger photo by Larry Kershner
Richard Cruse, gesturing in center, sits with farmers after his presentation to discuss how different tillage systems affect soil profiles. “What you do on the surface changes the environment underground,”?Cruse said. Cruse is director of the Iowa Water Center, based on the Iowa State University campus.
"Plants are designed to grow a set mass of roots,"?he said, "whether in shallow or deeper levels.
"You decide where the roots will develop."
Cruse offered the WANTS acronym and said if these aspects are followed, "the roots will respond."
Strength of soil's compaction.
Cruse focused on the compaction component saying that tillage of virtually any kind will cause soil compaction.
He said conventional tillage creates soil that is addicted to tillage.
"Soil strength increases,"?Cruse said, "as tillage intensity increases.
"Under well-managed no-till systems, there is less compaction and less resistance to root growth."
He said that no-till systems work best for good soil managers, but acknowledged that wetter growing seasons are challenging for no-tillers.
However, reduced tillage, he said, increases the soil's water-holding capacity since worm holes, which drain water deeper into the profile, are not destroyed; organic matter increases; and residue cover slows or prevents evaporation from the topsoil.
"My encouragement is don't till and don't remove residue,"?Cruse said. "But if you are tilling, I'd go with strip-till in this area (north central Iowa) but no-till in loess soils."
In general, Cruse said, cornfields can sustain half of the residue being removed from the surface.
He said it's essential to keep something covering the surface to protect from wind and water erosion.
"Your most important soil tool is organic matter," Cruse said.
Organic matter aids in soil retention, holds carbon in the profile and releases plant nutrients as it breaks down.
Quoting a 2007 soil erosion study by Stanford University, Cruse said, ""Data drawn from a global compilation of studies quantitatively confirm ... that erosion rates from conventionally plowed agricultural fields average one to two orders of magnitude greater than rates of soil production."
Setting the current drought period aside, Cruse said the number of one-day, four-inch or more rain and snow events has doubled over the last century.
Cover crops and/or plant residue protects the soil from the pounding of heavy rain and runoff.