Rainfall takes toll on soil

The record rainfall of 2018 combined with ever-heavier harvest and manure application equipment made for excessive compaction on many farms across the state.

In addition, the wet weather meant that fewer acres than normal were planted with a cover crop last fall. Unfortunately, correcting the sins of compaction may require multiple strategies over the course of the growing season.

Compaction has been shown to reduce crop yields by up to a third, and it can take up to 10 years for some top soils to recover from compaction. Once subsoil is compacted, it is extremely difficult to naturally recover. Soils that receive regular tillage are prone to more severe compaction due to the destruction of soil aggregates, while no-till soils become more resistant to compaction with time.

Unfortunately, heavily compacted no-till fields may need tillage to correct the issue as planting and harvest equipment may not be able to traverse rutted areas.

If ruts are present, the soil structure in the bottom of them may be destroyed, resulting in standing water. If so, a subsoiler or chisel plow operated deep enough to fracture the bottom of the ruts may help water percolate into the subsoil. This should occur when the ruts have dried out to promote soil fracturing and avoid further compaction.

A leveling pass should be completed with a tool that leaves surface residue, such as a field cultivator, with a disk being the least preferred option. Tillage of long-term no-till ground can lead to clod problems, loss of soil support, damage to natural root and earthworm channels and increased risk of recompaction. Therefore, you want to limit the intensity of tillage to the bare minimum necessary to restore the soil to productivity.

If rutting is limited to less than 20 percent of the field, localized remediation is enough, and the entire field does not need to be leveled.

Looking long-term, transitioning back to no-till and utilizing cover crops are extremely effective in controlling compaction. No-till allows aggregates to form through wetting-drying processes, fungal hyphae growth and plant organic matter addition and earthworm and root activity create large pores for water and air to move.

Cover crops are also a successful compaction fighting tool as they offer another set of roots to loosen soil in any given year. Some of our best cover crops for fighting compaction include radishes and annual ryegrass. A mix of the two is particularly effective as the taproot of the radish is complimented by deep fibrous roots of annual ryegrass.

Red and sweetclover also grow taproots and can decompact soils.

If ruts persist into the spring, consider growing sorghum-sudangrass crop in affected fields. The crop is especially effective at loosening soils and can be grazed, chopped or baled and wrapped. This warm season grass can be planted later than corn yet still grow large amounts of feed, giving one time to repair ruts in the late spring.

Sorghum-sudangrass can then be followed in the fall with a cool-season cover crop to further correct compacted soils.

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