Nitrogen leaching greatly impacts bacterial community and denitrifiers abundance in subsoil under long-term fertilization

For surface soil (0–10 cm), the bacterial communities were mostly correlated with electrical conductivity (EC), whereas the bacterial communities in soil below 10 cm showed a highest correlation with nitrate. QPCR revealed that topsoil harbored a greater abundance of denitrifiers than subsoil. Fertilization enriched denitrifiers in most soil layers in the profile.

However, the increase in the range of de-nitrifier abundance did not reach the increase in the range of nitrate. Further analysis found that denitrifier abundance was most positively correlated with soil organic carbon, indicating that the carbon-limit restricts the growth of denitrifiers in subsoil. These results reveal that the vertical separation of bacterial communities is largely controlled by soil resource partitioning, and nitrate leaching greatly contributes to shaping bacterial communities in subsoil in intensive agricultural systems, and further suggest that the impact of long-term fertilization on some microbial functions may be greater in subsoil than in topsoil.