The optimization of sewage sludge and effluent disposal on energy crops of short rotation hybrid poplar

An experiment was set up to test the effect of sewage sludge application and waste water irrigation on the biomass production of two poplar varieties, Populus trichocarpa x P. deltoides “Beaupré”, and Populus trichocarpa “Trichobel”. Three sludge applications were examined factorially with two irrigation regimes (with and without), over the two final years of a three-year rotation. The effects of treatment on soil and soil water were monitored, and the amount of heavy metals removed in the biomass was quantified. Irrigation had a significant effect on biomass of both poplar varieties, with Beaupré yielding more than Trichobel. Sludge application was not effective in increasing biomass yield, but the experiment was valuable in identifying that modest amounts of sludge (approximately 100 m3 ha−1 yr−1) were acceptable environmentally and did not compromise biomass production. Cadmium uptake was detected in the poplar biomass, but the amounts were small and insufficient for poplar to be used in phytoremediation of metal-contaminated land.