| This study included a literature review, a greenhouse experiment, and a field installation to quantify the effects of municipal and industrial by-products on forest soils and tree growth. The literature review synthesized information on the benefits and hazards of boiler ash, biosolids, and paper mill residuals application and summarized recommended application rates for forest soils. The 15-week greenhouse study indicated that by-products [biosolids, boiler ash, and their coapplication] enhanced the growth of hybrid poplar clone NM-6 (Populus nigra x Populus maximowiczii) as much or more than inorganic fertilizers. Poplar biomass increased with increasing biosolids rates, and none of the poplars amended with by-products had metal concentrations greater than those amended with inorganic fertilizers. The installation of a long-term field study was documented in which aspen (Populus tremuloides Michx.) seedlings were planted on two northern Minnesota sites that were amended with the same by-products used in the greenhouse study. |
