Trees and shrubs suffering from shallow soil compaction (typically due to pedestrian use or vibrations caused by vehicular traffic,) or lacking vigorous root growth due to poor topsoil quality (lack of organic matter, nutrients, beneficial organisms, or aeration) are ideal candidates for air tilling. Since most of a tree’s roots proliferate near the surface where they have the best access to oxygen and nutrients, air tilling is excellent at promoting robust and uniform root growth. If it’s necessary to affect soil to a depth greater than 6-8 inches (15-20 cm), then it’s possible to combine air tilling with other methods such as radial trenching or vertical mulching.
While the tree health benefits of air tilling alone (decompaction and aeration) are significant, this method is often used for soil augmentation as well. Air tilling is a preferred method to make organic topsoil amendments, including nutrients and beneficial organisms, due to the uniformity of treatment. Often referred to in the industry as root invigoration, this type of soil enhancement has been proven to increase root development and lead to overall improvements in tree health. As with all tree health-care applications, one size does not fit all. Collaboration between the landscape architect and certified arborist, as well as other professionals such as soil scientists, is vital to determine the best course of action.
Air tilling is typically applied around tree trunks in a radius ranging from five feet to near or well beyond the dripline. The larger the area, generally, the more effective the treatment. The process starts with the removal of any turf or mulch within the specified treatment area. The soil is then tilled using an AirSpade. The operator can work in circular or linear patterns, moving the AirSpade at one to two feet (0.3- 0.6 m) per second until the soil is visibly loosened. Several passes may be required if the soil is heavily or deeply compacted. The tool is held vertically, directing the airflow straight down. If the tip of the tool is kept beneath the soil surface, noise can be greatly reduced. After the initial tilling, the specified soil amendments can be applied evenly over the decompacted soil. The amendment is then blended into existing soil using an AirSpade in the same way and to the same depth that the soil was originally tilled. Finally, organic mulch (often wood chips are preferable) is applied to the surface in a layer 2-4 inches (5-10 cm) thick. After air tilling, continued monitoring and irrigation may be required since the soil is very porous and can dry out quickly
Technical Applications Bulletin
To learn more about performing air-spading procedures, tree health care and preservation read the full article below.