A common stressor for plants and trees growing in yards is compacted soil. Soil compaction, one of a handful of potential soil problems, discourages root growth and prevents water, air, and necessary organisms from being spread out through the ground and available to plants. Trees growing in compacted soil have limited access to water, especially since rain will run off (and perhaps flood lower parts of the yard) instead of filtering down into the soil. In addition, these trees have a greater risk of succumbing to injuries, infections, and infestations, since they are already under stress.
Soil compaction does sometimes occur due to normal rainfall, but it is also caused by frequent pressure on the ground. Areas where people or animals often walk may become compacted over time, and the passage of cars, large mowers, and heavy machinery can compact soil very quickly. Improper or badly-timed tilling can disrupt otherwise healthy soil, and completely collapse soils that are more prone to settling, including the many clay-heavy soils we have locally. Bare areas are more at risk of compaction than spaces with ground cover.
You can avoid causing soil compaction in your yard by making sure you have growth or mulch over the ground, walking as little as possible in areas that you want healthy growth, and ensuring that you don’t work the soil too often or when it is too wet or dry. If you have work done in your yard, you can ask your contractor to use the lightest vehicles possible to safely complete the job, and to put down plywood to protect the soil.
When you have compacted soil, there are a variety of ways to fix it. Adding organic material to your soil, such as compost, can change the composition of the soil so that it will better hold its structure. You can cover the compacted soil with a new layer of good, loose soil in places where you only intend to grow small plants with shallow roots; with time, earthworms and other creatures will loosen the soil below these areas and slowly undo compaction. Large lawn areas may benefit from aerators.
Over time, one of the best ways to decompact soil is to keep a layer of 3” of mulch on top. The natural breakdown of the mulch will support beneficial fungal growth which will naturally decompact the soil. For more information see: https://cuttree404.wpengine.com/benefits-wm-128.
If you have a lot of compacted areas, especially if your trees’ health is already suffering, it would be prudent to consult an arborist. A trained expert can discuss how to support your trees and avoid opportunistic infections while you are dealing with the soil problems, as well as advise you on how best to treat the compacted soil.