Temporal variation of diazotrophic community abundance and structure in surface and subsoil under four fertilization regimes during a wheat growing season

•Depth is the strongest factor influencing diazotrophic community size and structure.•Diazotroph abundance were related to bacteria in subsurface but not surface soil.•Abundant nifH genes could also be present in the deep soil layers.•Fertilization effect on diazotrophic community was significant but inconstant.