The majority of a tree’s important fine fibrous roots are distributed throughout the upper soil layers. These roots and their soil are the most critically sensitive area for a tree, with many of trees’ important biological processes and interactions with microbes, occurring in the soil immediately surrounding these roots. This makes trees incredibly vulnerable to soil compaction, which forces the air out of the soil, suffocating fine roots and affecting porosity and water movement through the soil. It also impoverishes the root/soil microbiome. Soil compaction is probably the single biggest killer of trees.
Soil compaction occurs from trampling (animal and human), movement and parking of vehicles, etc. It occurs much more readily when soil is wet and on soils with a higher silt and clay content, but all soil types can become compacted. Compaction damage occurs much more readily than most people realise.
It is therefore important to remediate compaction when it has occurred within a tree’s rooting area to restore root/soil ecosystem function and health. It will also be important to take steps to prevent soil compaction happening again in the future.
There are several ways soil compaction can be remediated, but best practice is always to use the least invasive method that will deal with the level of compaction found. This is because the more invasive the method used, the more potential there is to cause some fine root damage. Choice of de-compaction method is therefore an important decision, made by carefully assessing and weighing up the costs and benefits of treatment.
We use one or a combination of the following methods, choosing the most appropriate method/combination for the soil conditions found in the detailed soil investigation:
- Harnessing the power of earthworms! (least invasive).
The simplest solution to low to moderate levels of compaction is to take steps to encourage increased earth worm activity. Earthworms are nature’s soil de-compactors, playing a vital role in soil ecosystems.There are a number of ways of achieving this, the method we use will depend on the specific situation we find in the detailed soil and tree assessment.
- Decompaction with compressed air using the VOGT geo-injector (medium invasive).
If there is moderate to heavy compaction, and particularly if deeper soil levels are affected, then we might opt to use the VOGT, which injects compressed air into the soil, creating fissures in the soil, thus aerating it. Then an amendment would be injected into the newly created fissures to prevent them from settling and closing again. The artificial fissures aerate the soil enough to facilitate increased aerobic microbiological activity again, paving the way for earthworms to come in and disperse the amendments through the soil over time. This restores soil microstructure, improving water movement through the soil and restoring a favourable, aerobic rooting environment.
- Remediating severely compacted soils with an Airspade (most invasive).
There are a number of different techniques that we can use with the Airspade, depending on how deep the compaction goes and other site-specific details. As always, the technique used will be dictated by what we find in the detailed soil and tree investigation.