Arboriculture & Urban Forestry 37(6): November 2011 Arboriculture & Urban Forestry 2011. 37(6): 293–300 293 Evaluation of a Soil Decompaction and Amendment Process for Urban Trees Kelby Fite, E. Thomas Smiley, John McIntyre, and Christina E. Wells Abstract. Researchers investigated the effects of a soil decompaction and amendment process (AFM) and its individual components (air till- age, fertilizer, and mulch) on soil properties at four urban sites: Anderson, South Carolina; Boston, Massachusetts; Myrtle Beach, South Caro- lina; and Pittsburgh, Pennsylvania, U.S. At each site, 50 red maples (Acer rubrum) were growing on compacted and/or nutrient-poor soils whose pre-treatment bulk densities ranged from 1.14 to 1.74 g/cm3 . Treatments were applied in the autumn and winter of 2005–2006, and measurements were taken through the end of 2008. The AFM treatment significantly reduced soil strength relative to control at all sites in 2006. There were sig- nificant treatment × location interactions in all years, with higher bulk density sites (Anderson and Myrtle Beach) showing the greatest magni- tude and duration of response. The AFM and mulch treatments generally increased soil organic matter content, while air tillage alone signifi- cantly lowered soil organic matter content in Pittsburgh. At most sites, the AFM treatment was more effective than surface fertilizer application at improving soil fertility. AFM and mulched plots had significantly higher soil water content than other plots during periods of summer drought. Overall, AFM was effective in improving soils beneath established trees, and mulching was the most beneficial of the individual treatments. Key Words. Acer rubrum L.; Air Tillage; Decompaction; Fertilizer; Mulch; Organic Matter; Soil Strength; Urban Soils. Urban soils are a challenging medium for tree root growth. Construction activities and soil compaction create a below- ground environment that is resistant to root penetration, low in fertility, and prone to extremes of both drought and anoxia (Al- berty et al. 1984; Day and Bassuk 1994; Watson et al. 1996). Loss of topsoil and removal of fallen leaves limit the devel- opment of the upper organic horizon in which fine roots typi- cally proliferate (Fraedrich and Ham 1982; Harris et al. 2004). Successful strategies for the decompaction and amendment of urban soils would be useful to homeowners, municipalities, and tree care companies. Unfortunately, few effective options ex- ist. While soil compaction can be offset by mechanical tillage prior to planting, traditional tilling would cause significant root damage if performed beneath the canopy of established trees. A variety of pneumatic injection devices have been developed to physically fracture compacted soils with high-pressure air or nitrogen (Smiley et al. 1990). Such injections have seldom im- proved soil physical properties, and results have been highly de- pendent on location and soil type (Smiley et al. 1990; Rolf 1994; Smiley 1994; Smiley 2001). Air injection treatments had no ef- fect on trunk diameter growth in four tree species (Smiley 1994), and similar results were reported for shoot growth, plant height, and aboveground dry mass in five tree species (Rolf 1994). Vertical and radial mulching represent another approach to soil improvement. Vertical mulching involves drilling a series of shallow holes in the root zone and filling them with compost, per- lite, fertilizers, or other materials. Few studies have examined its benefits. In one report, roots avoided the perlite-filled holes (Ka- lisz et al. 1994); in a second report, tree growth responded as well to empty holes as it did to those filled with fertilizer (Smith 1978). Replacing larger soil volumes in radial trenches, pits, or nu- merous small holes has shown greater promise. Research by Watson et al. (1996) and Watson (2002) reported deeper rooting and denser root growth in the amended fill soil of radial trenches, as well as larger growth rings following soil replacement. These results suggest that the magnitude of the replaced soil volume may be critical in determining the success of the treatment. Recently, a process designed to decompact a portion of the root zone while simultaneously incorporating organic matter and fertilizer into the soil was tested. Reported here are chang- es in soil chemical and physical properties associated with the decompaction and amendment process (AFM) and its indi- vidual components (air tillage, fertilizer, and mulch) beneath red maples (Acer rubrum L.) at four urban locations. Specific objectives of the study were 1) to test whether soil strength, organic matter, fertility, and water content would be improved by the AFM treatment, and 2) to determine whether any indi- vidual component produced results similar to the full process. MATERIALS AND METHODS Site Characterization The study was conducted on 200 red maple trees at four loca- tions: Anderson, South Carolina (city park and recreation fa- cility); Myrtle Beach, South Carolina (street tree plantings); ©2011 International Society of Arboriculture
November 2011
| 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
