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Spring a good time to assess soil compaction in your fields

Spring is often the perfect time to examine soils for evidence of compaction, said DeAnn Presley, Kansas State University Research and Extension soil management specialist. It also happens to be a time when soils are often vulnerable to compaction.

"Fields should be assessed when the soil is at or near field capacity, the point at which the entire soil profile is moist, but not saturated. These conditions typically occur in the spring, although topsoils in much of Kansas are very dry so far this spring," she says.

Compaction occurs when soil particles are pressed together, limiting the space for air and water. The amount of soil water present is a critical factor in soil compaction potential.

If compaction is suspected, it can be confirmed by using a shovel or soil probe, Presley says.

"With a shovel, look for either a surface crust, or for platy soil structure (soil structure that resembles a stack of dinner plates). With a soil probe, push the probe into the soil slowly, and feel for a layer of increased resistance. Quite often, if a compacted subsurface layer is present, you can punch through the tillage pan, and the soil beneath it will have less resistance," she says.

Cone penetrometers may also be used to locate compaction, Presley adds.

"Penetrometers need to be used in combination with some device to assess soil moisture and texture, like a soil probe. Readings should be taken when the whole profile is at or near field capacity, approximately 24 hours after a soaking rain. If the soil is too wet, compaction could be underestimated because the soil water acts as a lubricant. If the soil is too dry, compaction could be overestimated because roots will be able to penetrate the soil when it re-wets," she says.

The idea behind using the penetrometer at field capacity is that this is the best-case scenario to mimic the penetration power of roots, she says.

"If using a penetrometer, push or drive it into the soil at a rate of 1 inch per second. Record the penetration resistance at each depth increment. Note the depths at which the penetration resistance exceeds 250-300 pounds per square inch (psi), a range that is root-limiting when the soil is moist," Presley says.

Spring is often the perfect time to examine soils for evidence of compaction, said DeAnn Presley, Kansas State University Research and Extension soil management specialist. It also happens to be a time when soils are often vulnerable to compaction.

The best cure for soil compaction is by not working or driving on soils that are too wet, Presley says.

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