Organic Mulch and Grass Competition Influence Tree Root Development

Abstract

Root density, soil moisture content and soil oxygen diffusion rate (ODR) were measured under three soil surface treatments—grass, organic mulch and bare soil. Seven tree species were tested, green ash, little-leaf linden, pin oak, red oak, sugar maple, red maple and Norway maple. All trees were approximately 20 years old. Elimination of the grass resulted in consistent increases in tree root density at the 0 - 7.5 cm depth, except for the oaks. Application of mulch increased root densities in the soil beneath it. The layer of decomposing organic mulch also provided additional medium for root growth. When compared to the grass treatment, total root surface area was increased up to 195 percent by the mulch treatment and up to 113 percent by the bare soil treatment. Soil moisture was significantly higher in the mulch and the soil beneath it and lowest in the grass treatment. ODR was unaffected by the treatments.