Soil glomalin-related protein affects aggregate NO fluxes by modulating denitrifier communities in a fertilized soil.

Agricultural ecosystems contribute significantly to atmospheric emissions of soil nitrous oxide (NO), which exacerbate environmental pollution and contribute to global warming. Glomalin-related soil protein (GRSP) stabilizes soil aggregates and enhances soil carbon and nitrogen storage in agricultural ecosystems. However, the underlying mechanisms and relative importance of GRSP on NO fluxes within soil aggregate fraction remain largely unclear. We examined the GRSP content, denitrifying bacterial community composition, and potential NO fluxes across three aggregate-size fractions (2000-250 μm, 250-53 μm, and <53 μm) under a long-term fertilization agricultural ecosystem, subjected to mineral fertilizer or manure and their combination. Our findings indicated that various fertilization treatments have no discernible impact on the size distribution of soil aggregates, paving the way to further research into the impact of soil aggregates on GRSP content, the denitrifying bacterial community composition, and potential NO fluxes. GRSP content increased with the increase in soil aggregate size. Potential NO fluxes (including gross NO production and NO reduction and net NO production) among aggregates were highest in microaggregates (250-53 μm), followed by macroaggregates (2000-250 μm) and lowest in silt + clay (<53 μm) fractions. Potential NO fluxes had a positive response to soil aggregate GRSP fractions. The non-metric multidimensional scaling analysis revealed that soil aggregate size could drive the denitrifying functional microbial community composition, and deterministic processes play more critical roles than stochasticity processes in driving denitrifying functional composition under soil aggregate fractions. Procrustes analysis revealed a significant correlation between denitrifying microbial community, soil aggregate GRSP fractions, and potential NO fluxes. Our study suggests that soil aggregate GRSP fractions influence potential nitrous oxide fluxes by affecting denitrifying microbial functional composition within soil aggregate.