Abstract The aim was to assess the effect of straw biochar on microbiomes along the depth (30–80 cm) of two coarse sandy subsoils. We hypothesized that biochar modifies extracellular enzyme activities (EEA), and diversity and structure of microbiomes across the subsoil depths. Two subsoils were amended with straw biochar (0%–4% w/w) and incubated for 16 months in a column experiment with two cultivations of spring barley. EEA were assessed using fluorogenic assays, while the prokaryotic and fungal communities were…