Are your soils compacted?

01/19/2012 @ 10:13am

If your soils are frozen and hard as a rock, this may not be in the cards for you just yet. But, if your temperatures are around the freezing mark, one way to stave off winter cabin fever and improve your crop potential this coming spring may be to get out in the field and do some soil sampling, namely to see if your fields have compaction issues.

You can learn a lot by simply probing your soil this time of year, says DeAnn Presley, Kansas State University Extension soil management specialist. There's a lot you can't do anything about -- like topsoil depth and soil textures -- but taking samples right now can help you note those things you can improve upon in time for this spring's planting.

"If you have never done so, you can learn something about the soil profile. How many inches of topsoil do you have? At what depth do you encounter changes in soil textures? Topsoil thickness and soil texture are two properties you can’t really control, at least not in the short term," Presley says. "One thing you can certainly look for and work on improving, however, is the density of your soil and whether there are any layers of compaction."

There are a couple of ways to see if your soils are compacted. First, you can take the "scientific approach" that measures soil density by finding the dry mass through a series of lab procedures. Find out more about this approach here.

"In scientific research, this method is used to analyze the effects of different management practices on soil quality, the differences between soil types, and other factors," Presley says. "It can also be used to quantify the differences in soil density at various depths within the soil, which helps in research on soil compaction."

A less precise but more practical method is what Presley calls the "hands-on" approach. This comprises simply noting any compaction by taking a soil profile with a spade, tile probe or soil probe. Even in a vertical soil sample, compaction isn't too tough to find.

"One approach is to dig a small hole about a foot deep, as if you were digging a post hole. You can take a knife and poke into the side of the hole, feeling for layers that seem denser, or that have a platy, compressed soil structure," she says. "Use a tape measure to determine the depth at which the dense layers occur. Then walk to a nearby fence row or waterway and do the same thing. Does this soil look and feel different? How does this compare to the endrows?"

If either of these methods turns up compaction, make sure any action you take addresses the specific area where you've got problems. For example, if you're finding compaction in the top 3 inches of the soil, Presley says it's likely a traffic issue. "Running properly inflated tires, using floatation tires, and having more tires in general helps to decrease surface compaction. Of course it will also help to keep traffic off the soil as much as possible when the soil is wet," she says.

If you find compaction deeper than 6 inches -- something it's important to distinguish between changes in soil texture, Presley says -- tillage with a moldboard plow or subsoiling may be necessary to break it down. To avoid future subsoil compaction is to change to a system of controlled traffic lanes in your fields. In a conventional system, as much as 90% of the field's surface sees tire tracks at some point during the crop year. Moving to a controlled traffic lane system can not only minimize surface compaction, but also improve machinery efficiency and floatation.