Range analysis of Eucalyptus globulus bark low-temperature hydrothermal treatment to produce a new component for growing media industry

Abstract

The use of industrial Eucalyptus globulus bark residues for organic growing media formulation was studied. Hydrothermal treatments were tested using Response Surface Methodology approach. Model design consisted of twelve combinations of temperature (T: 60-140 °C) and residential time (t: 20-60') to evaluate the effect on bark properties. Temperature had a significant effect in C mineralization and N immobilization rates, where the lowest responses (111.8 mmol CO₂ kg^-1 d^-1 and NIR = 4.1 mmol N kg^-1 d^-1, respectively) compared to IEB (214.6 mmol CO₂ kg^-1 d^-1 and 8.9 N kg^-1 d^-1, respectively) were suggested after modeling at 40 °C during 70'. Industrial bark was phytotoxic and treatments were effective for phytotoxicity removal. Industrial bark presented high air content but low water availability; treatments had no effect on bark physical properties and the use of demineralized water may have leached nutrient content. Results from pot experiment recommend the use of 25% (v v^-1) of treated barks in future growing media formulations.

Keywords: Forest residues; Growing media; Hydrothermal treatment; Microbial activity; Phytotoxicity.