Soil Repair

Soil Repair

The most significant threat to tree health in an urban setting is soil compaction.Often times construction, pedestrian traffic, new landscaping, and an array of other things can lead to soil compaction. Soil conditions are extremely important to root development and are usually a direct reflection of a tree’s health. Nutrient rich un-compacted soils have an abundance of open spaces and small voids within the soil structure. These voids and spaces are commonly referred to as pores. These pores are where fibrous roots develop and thrive. The fibrous roots of a tree are responsible for up to 90 % of the tree’s nutrient and water uptake. Roots breathe and absorb water and nutrients through these pores. When compaction occurs it reduces and sometimes completely eliminates pore space in the soil. As a result, the roots are suffocated and unable to transport water and nutrients to the tree. In most cases the tree will be sent into a mortality spiral and die.

The following are services that can assist in alleviating compaction and restoring tree health. All services are performed with our specially designed air tool that utilizes compressed air to gently remove soil from around the roots without damaging them.

Root Collar Excavation (RCX)

Root-Collar-ExcavationA root collar excavation is a simple process that is performed with our specially designed air powered excavation tool. The tool uses compressed air about 90-120 PSI to fracture soil clumps and compacted layers within the soil. Once the soil has been excavated to a depth of 6-12 inches the root collar will be exposed. This process is not only a great way to help reduce compaction, it is also a method that allows us to inspect the root collar of a tree for defects. Most root collar excavations are only done in the immediate area of the tree trunk. This is where the root collar is found.

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Radial Trenching

Radial TrenchingRadial trenching uses the same basic air powered extraction methods as a RCX. The key difference between a RCX and radial trenching is the area in which the soil extraction is focused. A RCX removes all of the soil surrounding the trunk of a tree1-4 feet from the trunk. Radial trenching utilizes channels that extend out from the trunk to the edge of the tree’s canopy or dripline. Trench patterns can be compared to bicycle spokes. The spacing between the trenches as well as their length is dependent upon the severity of the compaction or reason for the trenching. Trenches may be spaced 8-10 feet apart or more on a site where only minor damage has occurred and can be as close as one foot apart on severely compromised sites.

Soil Amendments

Soil AmendmentsAlmost as important as the aeration process is the reinstallation of amended soil. After excavating compacted soil it is important to make the necessary amendments to the soil structure and profile. A good healthy soil is comprised of 5% organic material, 50% pore space, and 45% minerals such as sand, dirt, clay, and rocks. Taking a soil sample to analyze the nutrient content is always recommended. Once the soil analysis is complete, a custom blend of nutrients can be added to the soil along with beneficial fungi and microorganisms such as mycorrhizae. Our certified arborists are experts in identifying soil deficiencies and making the necessary repairs.


It is important to install a fresh layer of organic mulch after the aeration and amendment processes. Mulch helps trees in so many ways. When properly installed, mulch will help tree roots retain moisture, assist in moderating temperature extremes, provide nutrients, reduce future compaction, and so much more. Mulch should usually be spread no more than 3 inches deep.

Recent Soil Repair Project

Here is a video of a recent soil repair project that we performed for a client:

We were recently contacted by one of the area’s premier builders to evaluate damage to a historic white oak on one of their new home sites. Prior to the building process, the contractor had retained our services to install a tree protection zone around a 175 year old white oak. The tree protection zone remained in place throughout the construction of the home and great care was taken to protect the tree. Unfortunately, in the eleventh hour the landscape contractor mistakenly removed the tree protection fence and installed sod up to the base of the tree. The soil within the tree’s critical root zone was tilled and leveled during the process and the pore space was compacted. The tilling removed some of the tree’s roots and the equipment compacted the soil. As mentioned earlier, compacted soil reduces a tree’s ability to uptake water and nutrients.

After inspecting the area we were able to formulate a strategy to help this tree survive. We performed the following steps:

The first step in the process was to delicately remove the sod that had begun to root.

After the sod was removed, we performed a RCX to aerate around the trunk and inspect the anchoring and buttress roots for damage. We found one root that was severed and performed a root pruning and bark tracing to assist the wound in closing.

We then started the radial trenching process. Because the area was so large, additional trenches were installed laterally between the main trenches. All main trenches were placed 3 feet off center.

The soil was amended with a custom blended solution that included a fertilizer high in phosphorous and mycorrhizae to promote root development.

We installed a layer of organic mulch and watered the tree to help with the stress associated with exposing roots to open air.

The tree is doing fantastically and is expected to make a full recovery. Hopefully it will live another 200 years.

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