Distinct responses of active and total bacterial communities to inorganic fertilization in a 30-year experimental site

Soil microbial communities play a vital role in mediating nutrient turnover, thus enhancing growth and development of plants. Understanding the dynamics of microorganisms in soils can provide insight into the influence of fertilization practices on improving soil fertility and plant growth in agricultural ecosystems. In this study, we compared the abundances and compositions of total (DNA-based, 16S rRNA gene) and active (RNA-based, 16S rRNA) bacterial communities at a 30-year experimental site in different inorganic fertilization treatments with different key elements (nitrogen, phosphorus, and potassium). The inorganic fertilizer amendments did not affect the abundance of total bacteria but significantly affected the abundance of active bacteria due to changes in microbial biomass carbon and NH 4 + -N contents. Cyanobacteria and Proteobacteria , especially for some dominant orders (e.g. Nostocales , Pseudanabaenales and Nitrosomonadales ) were the dominant phyla in the active microbial community and differed proportionally in nitrogen and phosphorus fertilized soil. Soil N speciation (e.g. total N, NH 4 + -N and NO 3 − -N) were the main determinants controlling the Cyanobacteria and Proteobacteria communities. Our results indicated that the unbalanced fertilization could reduce the abundance of active bacteria and significantly changed the dominant phyla compared with balanced fertilization. These findings provided an insight of composition and ratio of nutrient elements including nitrogen, phosphorus and potassium for managing future fertilization regimes in agricultural ecosystem. • The chemical fertilizers obviously affected active bacteria but not total bacteria. • Cyanobacteria and Proteobacteria were dominant in the active microbial community. • N availability was the main driver structuring Cyanobacteria and Proteobacteria . • Active bacteria was more sensitive than total bacteria to environmental change.