| Abstract |
A sustainable practice for Eucalyptus globulus bark valorization applying circular economy approach - a valuable waste stream from industrial pulpwood production in temperate regions - might be this fiber conversion into a new raw-material component for horticultural substrate industry. Forest-based materials, as alternatives to peat in growing media, are associated with inherent biological and chemical limitations, such as the presence of phytotoxic substances in fresh biomass and high microbial N immobilization. This study evaluates E. globulus bark aging treatment over successive periods of time (at 0, 4 and 12 weeks), and the effect of an initial amendment (220 mg N L-1), regarding substrate biological, chemical and physical properties. Fresh bark (FB) was phytotoxic: cress seed germination rate (GR) and root index (RI) were close to 0%, compared to peat control (GR and RI of 100%). Aging gradually removed the toxic effect; after 4 weeks FB showed GR=85% and RI>80%. On the 4th week of aging period FB chemical properties fitted within the recommended range for substrate use, excepting mineral N content. The aging process may promote N immobilization, however, and therefore initial substrate amendment is required prior to potting, thus providing enough nutrients according to plant needs. After seven days of incubation, aged bark pre-amended led to a lower N immobilization rate (0.02 mmol N L-1 day(-1)) than aged bark without N-supplement (0.29 mmol N L-1 day(-1)). The gradual addition of bark enhanced substrate aeration while water availability decreased. However, compaction risk may be reduced. Aged E. globulus bark can be blended up to 25% with peat and produce plants as good as in commercial peat-based substrates. |
