Establishment of poplars in soils amended with fibercake residuals from paper and containerboard production

Hybrid poplars (Populus sp.) are increasingly implemented in agroforestry systems across the U.S., mainly for their biomass production, carbon allocation, and ecosystem services. While agroforestry systems are usually established on marginal land, soil amendments, such as paper mill fibercake residuals, can provide necessary nutrients such as nitrogen (N) to increase poplar yield. To assess the effects of such amendments on poplar early growth and establishment, three clones (Populus deltoides Bartr. ex Marsh × P. maximowiczii A. Henry ‘DM114’; P. deltoides × P. nigra L. ‘DN170’; P. nigra × P. maximowczii ‘NM2’) were grown in a greenhouse for 35 days in soils amended with fibercake residuals from two northern Wisconsin sources (Expera Specialty Solutions, EXP, Rhinelander, WI; Packaging Corporation of America, PCA, Tomahawk, WI). Trees were grown in eleven different soil treatments (one potting mix control, one nursery soil treatment, and nine nursery soil-fibercake blends), with soils mixed according to tillable depth and N application rates. Expera treatments produced 4–30% greater values for growth parameters (excluding root number) and 2% greater values for biomass parameters (excluding root dry mass and root–shoot ratio) than other treatments containing fibercake (i.e., PCA and combined EXP + PCA treatments). Clone ‘NM2’ produced the greatest values for all parameters tested, while ‘DM114’ and ‘DN170’ values were typically intermediate and low, respectively. ‘NM2’ grown in Expera soils produced the highest values for all parameters, suggesting that ‘NM2’ has potential for greater early growth and biomass production on agroforestry sites amended with Expera fibercake.