Ferrie: Freezing and Thawing Cycles Can Help Or Hurt Compaction
It's beginning to look a lot like spring across much of the Midwest, and that’s not necessarily good news for fields going into corn and soybeans.
Fields would fare better if more freezing and thawing cycles occurred this winter to help reset soil density and kill a few more bugs, according to Ken Ferrie. He recently answered a farmer’s question about the value of such cycles.
“The grower heard us say during Corn College that freezing and thawing will not take out compaction layers,” says Ferrie, Farm Journal Field Agronomist and owner of Crop-Tech Consulting, Heyworth, Ill.
“In one of his college classes, they told him that the freezing-thawing process would take out compaction layers, so he's kind of wondering which way it really is.”
Ferrie says while freezing and thawing can help reset soil density, the process does a poor job of removing compaction layers. In some situations, the freezing-thawing process can make compaction even worse.
“I know that sounds wrong, but a sudden change in soil density can cause problems with root growth and water movement in the soil,” he says.
Soils Can Permit Or Restrict Root Growth
Loose soil at a field’s surface allows for the corn root system to get larger in diameter, from the start of growth. If the soil slowly tightens the roots will adjust to that tightening, and they will move on down into the soil.
“But if the soil suddenly gets tighter at a horizontal layer, the roots don't have time to adjust and they're going to turn and grow along the top of that layer,” Ferrie says.
Furthermore, the compaction layer creates a barrier that moisture won’t penetrate well.
“When we get rain, it soaks into the soil and it's going to stop at that compaction layer,” Ferrie explains. “The moisture is going to build up above that compaction layer because it's held up.”
Once winter freezes occur, the soils sitting above the compaction layer with water stored in them will expand at a much higher rate compared to the soil in and below the compaction layer. Those areas often contain reduced moisture levels.
Don’t Be Deceived By Appearances At The Field Surface
What often results from the moisture sitting on top of the compaction layer are ideal growing conditions at the soil surface, Ferrie notes. But the compaction problem remains, sometimes for years.
“I've personally found plow soles that were 20 years old and still restricting root systems and water movement,” he says. “This was in northern Iowa where it gets a lot colder than it does here in central Illinois.”
When farmers are able to till up compaction layers, freezing and thawing can be effective at expanding in all directions and start to rebuild and homogenize soil density.
Bottom line, Ferrie says, the freezing-thawing process is important to crop production but there are some things that it just can't do.
For more details on identifying compaction and addressing them, check out the following articles. Also, you can listen to this week's entire Boots In The Field podcast at the link below.
Do You Have Soil Compaction and Density Changes That Impede Roots and Water? Here’s How to Find Out
Shatter Your Yield Barriers One Layer At A Time
Ferrie: Does Spring Or Fall Horizontal Tillage Cause More Density Layers?
4 Stories to Learn More About a Vertical Tillage System
