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Tree Growth in Potting Media Made with De-inked Paper Sludge




De-inked paper sludge from a newsprint mill was evaluated as a substitute for softwood bark in container media. Whips, 1.2mtall, of 'October Glory' red maple (Acerrubruml), European birch {BetulapendulaMh), and 'Royalty'crabapple [MalusL.)were planted in 15-L plastic pots that contained potting media amended with 0%,20%, 40%, 60%, 80%, or90% paper sludge and 80%, 60%, 40%, 20%, 0%, or0%, respectively, bark (by volume). All media contained 10% sand. After 22weeks, plant heights, trunk diameters, and shoot dry weights were determined. Initial pH of media increased as the amount of paper sludge in the media increased, with the 90% sludge mix having pH 7.2. Paper sludge had a low initial CEC. Physical properties of all sludge-amended media were suitable for tree growth, but media containing 80% ormore paper sludge shrank in volume by 10% to 12% by the end of the study. All maple and crabapple trees grown in all sludge-amended media grew aswell asthose in 80% bark (control mix). In fact, mapleand crabapples trees in40% sludge produced at least10% and 36% more total shoot biomass, respectively, than trees in80% bark. Although birch trees grown in40% or60% paper sludge grew as well as control plants, those grown in 80% ormore sludge were at least 11% shorter and produced 24% less total shoot biomass (leaves, stems, and trunk dry weight) than control trees. These results demonstrated that de-inked paper sludge was a worthy substitute for upto 40% of the bark in a container medium for the three species tested.

Keywords: Oftwood bark plant heights dry weights initial CEC

Libraries: Floriculture

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