Wood Chips and Compost Improve Soil Quality and Increase Growth of Acer rubrum and Betula nigra in Compacted Urban Soil

Abstract

Tree growth is negatively impacted by the removal of topsoil and compaction of subsoil associated with site development in urban landscapes. A research plot with 60 Acer rubrum and 60 Betula nigra was created, mimicking the typical urban landscape disturbance. Wood-chip mulch (WC), compost (COMP), inorganic fertilizer (FERT), aerated compost tea (ACT), a commercial biological product (CBP), and a water control (NULL) were assessed for their impacts on soil quality and tree growth after five years. The WC treatment significantly decreased bulk density and increased soil moisture, organic matter, and microbial respiration. The COMP treatment increased soil moisture, organic matter, microbial respiration, pH, N, P, and K. Soil P increased with the FERT treatment. Tree growth was significantly increased with WC, COMP, and FERT treatments. No significant changes in soil properties or tree growth were observed with ACT or CBP compared to NULL; and, compared to background soil levels or other treatments (e.g., COMP and WC) ACT and CBP supply relatively minimal amounts of microbes and nutrients. This research shows strong evidence that COMP topdressings and WC mulches are effective and also cost-efficient methods for improving soil quality and stimulating tree growth in compacted urban landscape soils.