Previous research indicated that plant height and tillering contributed to the yield of switchgrass (Panicum virgatum L.) transplants that were spaced at distances of 30 to 107 cm. In Quebec, applications of 20 t ha(-1) biochar to a sandy soil increased switchgrass biomass fertilized at 100 kg N ha(-1). Therefore, the research objectives of this study were to determine whether or not (i) 10 t ha(-1) soft wood biochar affects traits that contribute to dry weight of fertilized switchgrass; (ii) these traits are affected by: a bacteriocin of Bacillus thurigiensis NEB17 (thuricin 17), a lipochitooligosaccharide of Bradyrhizobium japonicum 532C, and an experimental bio-fertilizer; and (iii) the path modeling of treatment effects change over time. The experiment was arranged as a randomized complete block design with 11 treatments. For the establishment year, semi-Markovian path models built on rank-transformed data indicate that biochar increased dry weight of the aboveground portion of biomass (b(Biochar, DW) = 0.20 +/- 0.15). The data from subsequent years indicate that the stems count per plant directly affected fresh weight (b(Stems,) (FW) = 0.65 +/- 0.09 in 2014 and 0.56 +/- 0.11 in 2015), which in turn directly affected dry weight (b(FW, DW) = 0.89 +/- 0.03 in 2014 and 0.83 +/- 0.05 in 2015). Thuricin 17 increased the switchgrass height (b(T17, Height) = 0.26 +/- 0.10 based on 2014 and 2015 combined data). In conclusion, biochar can increase switchgrass height and dry weight in the establishment year, thuricin 17 can increase plant height in post-establishment years, and therefore the effects change over time.
