Have you ever driven by and admired a beautiful new house, but then noticed that the older trees around it are looking rather sad? If not, take a closer look next time you drive by a recent construction site. Trees that seem to be suffering are a typical sign of soil compaction, and this is very common in areas that have had recent construction.
Unfortunately, compaction is one of the biggest risks to the long term health and growth of urban trees.
What is soil compaction?
Compaction occurs when excessive weight presses the soil particles together very tightly which reduces the pore space between them. These pore spaces hold air and water which is essential to the healthy functioning of a tree. The roots to take up water in the soil and they need air space in order to breathe.
Signs of soil compaction
If a tree on your property seems to be struggling and you’re concerned that it might be a result of soil compaction, here are some of the signs to monitor for:
- Chlorotic leaves: yellowing leaves that aren’t as deep green as they should be during the season
- Smaller leaf size: the tree’s leaves aren’t growing to a mature size
- Thinning canopy: when you look up into the canopy of the tree it doesn’t seem as full as it should be
- Early fall color: the tree’s leaves are prematurely turning red, orange or yellow in the spring or summer
Causes of soil compaction
Compaction is a result of excessive traffic or activity on the soil around the root zone. This is often caused by:
- Lawn maintenance activities: riding lawn mowers and tractors
- Foot traffic: humans walking in the same areas over and over again
- Vehicles: cars and trucks parked on or driving over the tree root zone
- Lack of drainage: wet soil over the long term can cause it to compact
- Construction activities: large equipment parked on or driving over the root zone, root cutting and disturbance
In all of these cases, the tree’s health will be negatively impacted due to the lack of water infiltration and nutrient flow and the greatly reduced gas exchange in the root system. These issues combine to stress the tree, and if left unchecked could result in girdling roots, increased susceptibility to insect and disease infestation, and in many cases death.
Air spading: The Solution for Compacted Soil
One of the best treatments for soil compaction around trees is Root Zone Aeration which employs the use of an air knife or air spade to loosen the soil around the roots of the tree. This can eliminate compaction, allow for any root pruning that’s needed, and make space for the addition of missing organic material and nutrients back into the soil.
The Air Spade uses compressed air forced through a supersonic nozzle that then loosens and crumbles the compacted soil. This exposes the tree’s root structure with minimal to no damage. Because tree roots are not porous, they are not disturbed by air excavation.
Exposing the roots will allow an arborist to assess the health of the root systems and take the steps necessary to safeguard your tree’s health. Oftentimes it’s necessary to prune away damaged roots. After this step the staff at Eco will also incorporate a high amount of nutrient rich, organic compost mixed with BIO-CHAR into the soil.
After air spading your tree will benefit from increased fine root growth, restored vigor and canopy growth. This process will help you avoid much more costly issues in the future and, more importantly, preserve the trees in your landscape.
Benefits of Air Spading
Now that you know what air spading is, let’s dive a little more deeply into the benefits.
- Soil compaction relief
This is the compaction relief that we mentioned. When construction occurs, soil compaction is a result due to heavy machinery driving over the soil. However, it can be caused by items seemingly as simple as walking. Think fairs with thousands of people walking over the root zones.
With spoke excavation, we air spade “spokes” out from the trunk to loosen the soil and add in nutrient-rich biochar. This increases root respiration and available water and nutrients, and allows soils to drain effectively. Pore space in the soil is created, which allows fine roots to grow into the air spaded areas.
Spoke excavation is especially effective when paired with growth regulator treatment. On their own, soils will take years and years to develop pore space. Air spading can accomplish the same thing in one day.
- Root inspection
Root inspections are important when a girdling root is present. When inspecting your tree, a Certified Arborist may notice a swollen trunk. This can occur when a root is wrapped around the trunk and not allowing water and nutrients to flow. Girdling is especially common in hybrid maples.
- Root barrier installation
We often see trees that are planted too close to patios or sidewalks. The concrete begins to push up and crack.
While this is never an ideal situation, there is a way to prolong the life of your tree by protecting the paved surfaces. By air spading the length of the paved edge, we are able to take a look for any large roots that are growing underneath that area.
The large roots are pruned and a barrier is installed to prevent further interference.
A similar approach can be used for root pruning near house foundations. Again, we suggest pairing this service with a growth regulator treatment in order to slow root growth and reduce overall stress.
- Root flare excavation
Occasionally, trees are planted too deep. While a tree can’t be dug up and replanted (we wish!), it is possible to excavate the soil around the trunk to help the issue. With the help of an air spade, the risk of wounding the trunk or roots with a shovel is avoided.
Prior to air spading, grass or items (eg: mulch or rocks) on are removed to expose the soil surface. Then, high pressure air is utilized to blow the soil away to expose the roots. This process is rather meticulous, though it may not appear that way with dirt flying everywhere! Once completed, the area can be reseeded as a lawn if necessary.
If you suspect compaction to be an issue with one or more of the trees on your property, contact an ISA Certified Arborist to review the site conditions, assess the health of your trees, and inspect the soil around the tree. In severe cases of compaction, the tree can often be saved, and its health improved, with the use of air spading.
If you live in the Madison, WI area, schedule your free consultation with an arborist here.