Chemical and bioassay characterisation of nitrogen availability in biochar produced from dairy manure and biosolids

► 6 M HCl acid hydrolysable forms of N in biochar were investigated. ► Influence of pyrolysis temperature on these forms also investigated. ► C and N cycling in biochar from different pyrolysis temperatures were studied. ► Modified C/N ratio for estimating net N mineralisation in biochar was proposed. ► Extraction of N with 6 M HCl could be used to estimate labile N in biochar.