Growth and biomass of Populus irrigated with landfill leachate

Resource managers are challenged with waste disposal and leachate produced from its degradation. Poplar (Populus spp.) trees offer an opportunity for ecological leachate disposal as an irrigation source for managed tree systems. Our objective was to irrigate Populus trees with municipal solid waste landfill leachate or fertilized well water (control) (N, P, K) during the 2005 and 2006 growing seasons and test for differences in tree height, diameter, volume, and biomass of leaves, stems, branches, and roots. The trees were grown at the Oneida County Landfill located 6 km west of Rhinelander, Wisconsin, USA (45.6°N, 89.4°W). Eight clones belonging to four genomic groups were tested: NC13460, NC14018 [(Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh) × P. deltoides ‘BC1’]; NC14104, NC14106, DM115 (P. deltoides × Populus maximowiczii A. Henry ‘DM’); DN5 (P. deltoides × Populus nigra L. ‘DN’); NM2, NM6 (P. nigra × P. maximowiczii ‘NM’). The survival rate for each of the irrigation treatments was 78%. The total aboveground biomass ranged from 0.51 to 2.50 Mg ha−1, with a mean of 1.57 Mg ha−1. The treatment × clone interaction was not significant for tree diameter, total volume, dry mass of the stump or basal roots, or root mass fraction (P > 0.05). However, the treatment × clone interaction was significant for height, total tree dry mass, aboveground dry mass, belowground dry mass, and dry mass of the leaves, stems + branches (woody), and lateral roots (P < 0.05). There was broad clonal variation within the BC1 and DM genomic groups, with genotypes performing differently for treatments. In contrast, the performance of the NM and DN genomic groups was relatively stable across treatments, with clonal response to irrigation being similar regardless of treatment. Nevertheless, selection at the clone level also was important. For example, NC14104 consistently performed better when irrigated with leachate compared with water, while NC14018 responded better to water than leachate. Overall, these data will serve as a basis for researchers and resource managers making decisions about future leachate remediation projects.