Date of Award

8-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Plant and Environmental Science

Advisor

Wells, Christina E

Committee Member

Smiley , Edgar T

Committee Member

Marren , David G

Committee Member

Bridges , William C

Committee Member

Caldwell , Judith D

Abstract

The Root Invigoration process involves soil decompaction with an air tool, amendment with organic matter and prescription fertilizer, and mulching. In the current study, we measured soil chemical and physical properties, tree characteristics, and root system responses to this process and its individual components. Treatments included Root Invigoration (AFM), mulch only (M), fertilization only (F), Airspade® tillage only (A), and an untreated control (C). The experiment was conducted from 2005-2007 at four urban sites: Anderson, SC; Boston, MA; Myrtle Beach, SC and Pittsburgh, PA. Soil strength was initially reduced by Airspade®, mulch and AFM; however only AFM-treated soils sustained this reduction over two seasons. Across all locations, soil organic matter content was increased with AFM and mulching. The levels of six soil nutrients were increased by Root Invigoration, while one nutrient was increased by an individual treatment. Tree condition ratings were significantly higher in AFM trees than control trees by the end of 2007. In two locations, increases in dbh were also greater for AFM trees. At the end of 2006, estimated chlorophyll concentrations were higher in AFM trees than in the A or M treatments. Foliage of AFM trees had higher levels of phosphorus and potassium than foliage of fertilized trees. Mulched soils (both AFM and M) frequently had higher soil moisture content. During a drought period in 2007, pre-dawn leaf water potential was higher for M trees on two dates and for AFM trees on one. Although there were differences in root length density (cm root/cm3 soil) among treatments in 2006, there were none in 2007. Mean root diameter was increased with fertilization. Root lifespan was reduced with M and AFM treatments. Time until root browning was also reduced with A, M and AFM, however AFM merely reflected the influence of the individual treatments. M and AFM shifted a greater proportion of fine roots to the upper 33.3 cm of the soil profile.

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Horticulture Commons

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