By Sjoerd Willem Duiker
Last fall was dry after a terribly wet year, and this fall has again been dry in many parts of the state. This presents an opportunity for subsoiling to alleviate soil compaction.
Soil compaction is the ‘silent thief’- it often causes small yield reductions, but these can last for many years. Subsoil compaction is the most pernicious, because it typically does not decrease yields by much, but the effects can last many years. In a multi-national soil compaction research project, surface compaction effects had disappeared a few years after the compaction event, but subsoil compaction effects below 12” depth, though small, were still observable 10 years after the compaction event that causes them. Subsoil compaction can be caused by very heavy axle loads (>10 tons per axle), by repeated tillage to the same depth, and can also be the result of natural soil forming factors. We saw a corn yield improvement of 11% by subsoiling a soil with a shallow fragipan, showing that subsoiling can benefit crops under certain conditions. We also saw significant yield improvement on severely compacted soils by manure hauling traffic on wet soils. But we did not see yield improvement from subsoiling on soils without naturally compacted layers that were not compacted by heavy traffic.
If you determine that subsoil compaction is a problem on your soil, this might be a good fall to alleviate it with a subsoiling operation. Although some parts of the state (primarily the southeastern part of Pennsylvania) received more rainfall, and soils might not be in the right condition to be subsoiled, dry soil conditions in most of the state present a good opportunity to remediate compaction. To determine if the soil is suited to be tilled, use the ’ball test’, by grabbing a handful of soil, kneading it, and if does not ball up, you are good to go. The aim is to improve soil physical conditions to stimulate biological activity, such as earthworm activity and root growth. Therefore, you don’t want to use a subsoiler that inverts the soil or leaves it so rough that secondary tillage is needed to create a level soil surface devoid of any cover. Instead, use a subsoiler with narrow shanks that are not parabolic and have attachments that help to keep residue in place. Residue cover is your protection from erosion, and also an essential food source for deep-burrowing earthworms. For maximum fracturing below the soil, use a subsoiler with large winged points, or a paratill subsoiler with bent-leg shanks. After the subsoiling operation, prevent recompaction by managing your field operation to dry soil conditions, keeping axle loads, and contact pressure low. Also, plant a cover crop after subsoiling to start rebuilding soil structure and stabilize the cracks you created in the subsoiling operation.
Source : psu.edu