Effect of solid residues from the cellulose industry on plant growth

An alternative use of solid organic and inorganic residues as fertilizers from a Kraft pulp industry was studied. Residues of inorganic nature, such as ashes, fly-ashes, dregs, grits, as well those rich in organic matter, primary sludge and brown stock rejects, were examined for plant growth enhancement. These residues, all alkaline in nature, used in different concentrations together with soil, bark, organic soil or mixed with a nutrient solution, were tested on the growth of Monterey pine (Pinus radiata), Eucalyptus globulus, rice (Oryza sativa cv. 'Diamante'), and duckweed (Lemna minor) under greenhouse and in-vitro conditions, respectively. Responses varied according to plant species, type, and waste content in combination with substrate. For Monterey pine, substrates including ash, fly-ash, and dregs promoted growth; in Eucalyptus seedlings dregs and fly-ash were also beneficial. Primary sludge and ash were favorable for rice growth. Duckweed increased frond number and plant biomass when grown in water containing fly-ash and primary sludge extracts, combined with nutrient salts.