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MADISON

During the 2016 harvest season for corn and soybeans since early September, many Wisconsin farm fields are sporting ruts that were created by equipment used during those harvests.

How to assess those ruts and what to do about them was the subject of a recent advisory by University of Wisconsin Extension Service soil scientist Francisco Arriaga and biological systems engineer Brian Luck.

In addition to sharing tips about how to reduce rutting during periods of soil saturation, the advisory described follow-up measures for the fields where ruts have been created. Arriaga and Luck emphasized that the presence of those ruts does not necessarily equate to soil compaction.

On what seems to be counterintuitive, the subsoil is less likely to suffer compaction when its pores are filled with water than when there's a portion of empty pores — a condition that's more accommodating to soil compaction or consolidation, Arriaga and Luck said.

Soil compaction check

To check on whether soil compaction occurred, use a penetrometer to determine the depth at which it exists, the advisory indicated. The follow-up corrective action would depend on whether the compaction is shallow (less than at 6 inches) or deeper in the subsoil (more than 6 inches).

For shallow compaction, Arriaga and Luck mentioned the possibility of planting a cover crop such as cereal rye with perhaps a legume mix — an option for which the remainder of the growing season is probably already too short in much of Wisconsin. They added that freeze and thaw cycles during the winter could alleviate shallow compaction but cautioned that this is not a guarantee.

If the compaction is deep, Arriaga and Luck suggested sub-soiling or deep strip tillage. They pointed that both the freeze/thaw cycle and trying to grow a cover crop in compacted subsoil are not likely to help in this situation.

Check for compaction both this fall and in spring to determine if a deep tillage operation is needed, Arriaga and Luck said. A demonstration on how to use a penetrometer is available on YouTube at https://youtu.be/Zq_785JqRq8?list=PLF17555C62D9A378B.

Seedbed preparation

In many fields, the saturated soils led to rutting and smearing the surface during the crop harvests in recent weeks, Arriaga and Luck observed. A minimum of light tillage — either before the winter freeze or after the thaw in the spring — will be needed in many cases.

Confine that tillage to the areas where there was considerable rutting or smearing, Arriaga and Luck continued. In those cases, a grass specie cover crop such as cereal rye could develop a fibrous root system that would improve the condition of the soil surface.

No till-fields are not likely to have suffered as much rutting or other soil damage as conventionally tilled fields, the advisory suggested. It added that, in the long term, soils in no-till fields have a greater ability to “bounce back” without a tillage intervention.

It will take the cooperation of the weather before soils freeze, but in all cases, soils need to dry before any remedial tillage occurs, Arriaga and Luck stressed. They can be reached by email to francisco.arriaga@wisc.edu and bluck@wisc.edu.

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