Close up of soil compaction in harvested corn field
RUT ROW: Wet fields and farmers trying to harvest crops led to a lot of compaction in fields. Planning and good crop rotations can help solve these compaction problems.

Compaction happened, now it’s time to fix it

Don’t just rip. Figure out how deep compaction is and have a good plan.

By Tom Kilcer

The soggy conditions that started in mid-July continued through harvest across most of New England, the Mid-Atlantic and the upper Midwest.

Corn silage was too dry to harvest, and fields were too wet to drive in. Dump wagons off-loading at the edge of the field, tractors pulling trucks as the chopper filled them, broken chains and cables were common sights. The result was a tremendous amount of soil compaction across all soil types.

It happened. Now we need to move forward.

Work in Canada has found that some damage from compaction — greater than 20 inches — is permanent. The ruts in your field may not be that deep, but the damage starts at the bottom of the rut and goes down from there.

Before you start ripping and tearing, you need to understand what is going on in the soil.  

See where compaction is
Hooking up to a deep ripper and blowing a lot of black smoke is not removing compaction. In New Zealand, researchers say: "Deep tillage without a change in the rest of the tillage/planting system is a waste of time."

If you don't have the deeper layers dry and friable, deep tillage will make the damage many times worse. Not only will you have vertical compaction, but if the tillage unit is working in wetter subsoil, this will also lead to lateral compaction. You will basically be turning the lower soil structure to the consistency of cement blocks. Continuing to plant corn and simply running a deep ripper through it will leave your soil permanently crippled and yield limiting.

Dig a hole before you rip and see where the compaction starts and finishes. The deep tillage needs to be 1 to 2 inches deeper than the compaction to lift and shatter the profile. In my field tests, anything less will just cut a compacted groove in a compacted layer. Check around the field as wetter areas may be deeper and drier areas may be shallower.  

Don't count on frost
Research has found that frost will not remove compaction. What is lifted by the frost settles to the same density after thaw.

A more effective system is a holistic approach with a mix of prescription tillage and fibrous deep-rooted crops. The latter is critical. If you loosen the soil and plant corn, there is nothing to stabilize it, and the structure will collapse again worse than before.

Lifting the soil to reduce compaction will simply collapse, especially with the next pass, unless you are doing something to hold it open. It needs to be a process over multiple steps, integrated with deep-rooted crops that will sustain the tillage.

The stabilizing crop bridges the gaps and helps to hold open the voids you created.

Work ground when friable
Unless your area has a very dry spring, you will not be able to remove any compaction early next spring. As soon as the ground is friable, work the top 6 to 7 inches with a chisel and plant.

Resist the temptation to run the chisel as deep as it can go. First, the lower layers are likely still too wet, and you will enable the lower layers to laterally compact even if the top looks nice. Second, when you operate deeper than the vertical portion of the curve of a chisel, you are now pushing down and out, not lifting up. This compacts the soil further, and I have seen it make compacted curled bricks of the field.

I would not use a disk to finish behind the chisel as this will leave a root-limiting disk pan at 4 inches. Most farmers I work with have switched to levelers attached to the chisel for one-pass preparation.

Repeat treatments
You will not remove compaction in one swoop. It will take a repeated treatment over time.

Rotation is a big help, as perennial crops' roots will grow in times when the soil is softer. Don't think that by simply planting a few months of tillage radish this is going to magically cure all your issues. On the flip side, rotations do not mean taking your corn

ground out for 10 years of hay. You need to maintain your diverse forage system. Short-term rotations will allow you to target compaction to damaged fields while simultaneously maintaining the quality and quantity of forage needed.

Plan good crop rotations
The most critical part is to plan a system for removing compaction. Sod-type crops alone will not remove compaction.

We dug in an alfalfa timothy stand that had been grown for 15 years. We could still see the plow marks, and there were no roots below 7 inches.

You still need to grow corn for energy. Swap out sod fields for corn as they hopefully were not compacted and rutted during harvest. They will also give 15% to 20% higher yield than corn after corn.

One system for very damaged fields is to leave them until after first-cutting hay. Usually, the soil is much drier then. Try some deep tillage and then plant BMR brachytic dwarf-type sorghum in narrow — 15-inch or drilled at 8 to 10 pounds of seed per acre — rows. Sorghum has a very different root system than corn. They excel at penetrating deep into the soil profile to give stability to the recently loosened soil. As this crop can come off earlier than corn, you can deep till again at a slight angle and plant a winter forage. Winter forage yield has actually doubled where we have done this. The following spring, you can either go back to corn or no-till a hay crop.

If sorghum is not your choice, then plant a shorter-season corn so it is harvested early. You can then till in late August or early September, and then plant winter forage 10 days to two weeks before wheat planting date. This will produce good fall root mass that will follow the newly created voids deep in the soil.

Try winter forage
Winter forage is one of the best crops to rapidly improve soil structure. Work in the Carolinas' coastal plain found that the roots penetrating the ripped voids leave a coating of organic matter that keeps it from reconsolidating in a compacted mass.

In the spring, after the winter forage is harvested, no-till alfalfa or red clover for 2 to 3 years of perennial forage. Not only do they stabilize the deep-tilled soil in a less-dense condition, but the perennial roots grow when the ground is soft and can continue to penetrate any small cracks.

Kilcer is a certified crop adviser in Kinderhook, N.Y.

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