Fertilization enhances mineralization of soil carbon and nitrogen pools by regulating the bacterial community and biomass

Abstract

The stability of soil organic matter is a key predictor of changes in management practices due to the progressive decomposition of organic compounds. However, the dynamics of soil compounds and to what extent the composition of microbes controls the process are still unclear. Black soils from Northeast China without fertilizer (CK), soil treated with chemical fertilizer (NPK), NPK plus maize straw (NPKS), and NPK plus cattle manure (NPKM) were collected and separated into the labile fraction (macroaggregates > 150 μm) and the recalcitrant fraction (microaggregates 150 μm) for a 14-day incubation. The net carbon (C) and net nitrogen (N) mineralization potentials of the labile fraction were 15.87–26.11 and 0.74–1.48 mg kg−1 soil day−1, respectively, which were between 1.4 and 2.3 times higher than those of the recalcitrant fraction. Compared with CK, NPKS and NPKM significantly increased C and N mineralization in the labile fraction but not in the recalcitrant fraction. Boosting regression tree analysis suggested that total nitrogen (TN), microbial biomass nitrogen (MBN), and bacterial abundance accounted for 48.9%, 31.7%, and 14.0% of the total net C mineralization, respectively. Additionally, soil organic carbon (SOC), microbial biomass carbon (MBC), and bacterial abundance accounted for 39.4%, 37.3%, and 22.1% of the total net N mineralization, respectively. Path analysis showed that TN, MBN, and Brevundimonas positively influenced soil net C mineralization. SOC and MBC positively affected soil net N mineralization, whereas unclassified Comamonadaceae had a negative impact. The mineralization of soil C and N was affected by the inputs of external inorganic nutrients and organic materials and was attributed to the bacterial community, in which Brevundimonas positively responded and contributed to mineralization, while unclassified Comamonadaceae responded negatively.