Miscanthus biochar promotes growth of spring barley and shifts bacterial community structures including phosphorus and sulfur mobilizing bacteria

•Biochar soil amendment significantly promoted growth of spring barley.•Biochar soil amendment significantly altered bacterial community structures.•S and P mobilizing bacterial abundances significantly increased with biochar addition.•Stepwise regression attributed 74% of plant growth to P and S mobilizing bacteria.•Pyrolysis of Miscanthus grass produced biochar with sulfate ester as main S source.