The Quebec government has established a program to treat industrial and domestic wastewaters. However, this program does make it necessary to dispose of large quantities of sludge. This sludge can be burned or landfilled but such solutions do not properly draw benefit from the sludge's potential as a fertilizer. There is a considerable interest in composting of the sludge. In this study, compost from the composting plant in Plattsburgh was mixed with the growing substrate normally used for the production of containerized jack pine (Pinus banksiana Lamb.) seedlings to determine if the compost could be used for the production in containers of forest seedlings. The growth of containerized seedlings produced with proportions by volume of 80% peat moss and 20% vermiculite was compared to the growth of seedlings when the peat moss (80%) was replaced by different proportions of compost (20, 40, 60, and 80%). After one growing season in tunnel, the best growth rates in terms of shoot height, root-collar diameter, and dry biomass were obtained with the control, followed in decreasing order by the treatments compost 20, 40, 60, and 80%. In this experiment, the use of compost from wastewater treatment plants reduced significantly the growth of jack pine and this can be explained mainly by the lack of nitrogen in the tissues of jack pine seedlings. However, the adjustment of nitrogen fertilization and conditions of cultivation by using compost may permit the production of containerized seedlings having the same dimensions as the controls. The seedling growth parameters when 20% compost was incorporated in the substrate were nearly the same as the control seedling. Key words: sludge, recycling, compost, substrate, container, forest seedlings, jack pine.
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