Soil Microbial Community Stability Is Regulated by Soil Bulk Density and pH Under Contrasting Long‐Term Fertilization

ABSTRACT Fertilization management changes soil quality, as well as the microbial community structure and its stability. However, little is known about how the temporal stability of the soil microbial community responds to soil quality in agroecosystems. To fill this knowledge gap, this research was implemented based on a long‐term field experiment (1982–2015; 33 years at the time of sampling in 2015) with the following treatments: no fertilization (NF), natural regeneration (NR, no fertilization and no tillage), mineral fertilization (NPK), and mineral fertilization combined with either wheat straw (WS) or cow manure (CM) returned to croplands, and selected 14 soil parameters for soil quality calculation. By analyzing microbial community stability with seasonal changes using co‐occurrence networks, we found that the temporal robustness, vulnerability, and composition stability of soil bacterial and fungal communities did not correlate with soil quality. Soil quality was closely related to fertilization regime ( F value = 156.01, p < 0.001) but not to seasonal changes. Among the soil quality parameters, soil bulk density was important as well as soil pH and microbial diversity, but its direct contribution to the bacterial (19.3%) and fungal (−15.1%) composition stability was more than the bacterial Shannon index (7.4% and −6.5%) and dissolved organic carbon (8.8% and −9.9%). These results indicate that high soil quality does not necessarily imply a higher temporal stability of the soil microbial community. Soil bulk density, as well as soil pH and microbial diversity, should be considered in future analyses of microbial community stability in agroecosystems.