428 Hascher and Wells: Effects of Soil Decompaction and Amendment Arboriculture & Urban Forestry 2007. 33(6):428–432. Effects of Soil Decompaction and Amendment on Root Growth and Architecture in Red Maple (Acer rubrum) William Hascher and Christina E. Wells Abstract. The TerraventTM soil injection device (Pinnacle Concepts, Ltd., Cornwall, UK) uses compressed nitrogen gas to fracture compacted soil and permits the subsequent injection of liquid amendments. In the current study, we measured fine root growth and architecture in soil that had received one of four treatments: 1) Terravent injections, 2) Terravent injections followed by liquid amendment (MycorTree Injectable; PHC, Inc., Pittsburgh, PA, U.S.), 3) addition of amendment only, and 4) an untreated control. The experiment was conducted on ten red maples (Acer rubrum) growing on a moderately compacted urban clay soil next to a busy road on the Clemson University campus. Treatments were applied in April 2002. Seven weeks later, soil cores were pulled from locations adjacent to the injection sites, and fine roots (less than 2 mm [0.08 in] in diameter) from each core were washed free of soil. A variety of root parameters were measured, including length, surface area, diameter distribution, and mass. Terravent treatment had no effect on any root parameters measured. Appli- cation of MycorTree was associated with small, statistically significant reductions in root diameter, root mass density (mg root/cm3 soil), and root surface area density (cm2 root/cm3 soil). Key Words. Acer rubrum; root growth; soil decompaction. Urban soils experience significant compaction as a result of mechanical disturbance and grading during construction. Later, these soils may be further compacted by pedestrian, equipment, and vehicular traffic. Consequently, urban soils frequently exhibit significant resistance to root penetration, reduced water infiltration, and low rates of oxygen diffusion, all of which can impair the growth and function of tree roots (Patterson and Mader 1982; Day and Bassuk 1994). Pneumatic injection devices for the mitigation of soil com- paction around urban trees were first introduced in the early decades of the 20th century. These devices injected pressur- ized air into the soil to fracture compacted layers and improve root growth conditions. Some were fitted with a hopper from which dry fill material could be released into the fracture planes to hold them open (Smiley et al. 1990). Research has not demonstrated a consistent benefit to soil treatment with pneumatic injection devices. Air injections have sometimes improved soil physical properties, but these results have been highly dependent on location and soil type (Smiley et al. 1990; Rolf 1994; Smiley 1994, 2001). Air injection treatments had no effect on trunk diameter growth in four tree species (Smiley 1994), and similar results were re- ported for shoot growth, plant height, and aboveground dry mass in five tree species (Rolf 1994). To date, no research has addressed fine root growth re- sponse to soil injection treatments. Injection treatments have the potential to reduce mechanical impedance and increase root elongation in compacted soils. Furthermore, the opening ©2007 International Society of Arboriculture of cracks and fissures may increase water and oxygen avail- ability in the root zone, stimulating root growth and activity. In this experiment, we evaluated a relatively new soil in- jection device, the TerraventTM (Pinnacle Concepts, Ltd., Cornwall, UK), for its ability to increase fine root length density of red maple (Acer rubrum) growing in moderately compacted urban soil. The Terravent injects high-pressure nitrogen gas through a perforated steel pipe that is driven into the soil. Previous work has shown that the resulting fractures occur approximately 23 cm (9.2 in) below the soil surface and are horizontal to convex with widths up to 56 cm (22.4 in) (Smiley 2001). After the initial high-pressure nitrogen injections, liquid amendments may be released into the fractures. In this ex- periment, a commercial liquid soil amendment containing mycorrhizal inoculum and numerous other ingredients (My- corTree Injectable; PHC, Inc., Pittsburgh, PA, U.S.) was tested with and without initial Terravent injections. MATERIALS AND METHODS Site Characterization The study was conducted on ten red maple (Acer rubrum) trees growing along a busy road at the Clemson University campus in Clemson, South Carolina, U.S. The trees ranged in diameter from 28 to 66 cm (11.2 to 26.4 in) and had canopy diameters ranging from 6 to 9 m (19.8 to 29.7 ft). The larger
November 2007
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
