Long-term manuring facilitates glomalin-related soil proteins accumulation by chemical composition shifts and macro-aggregation formation

Glomalin-related soil proteins (GRSP), derived from arbuscular mycorrhizal fungi (AMF), contributes significantly to soil stability and carbon sequestration. However, the responses of GRSP accumulation and associated AMF community and diversity to long-term fertilization regimes remain unclear. Here, we investigated the dynamics of GRSP contents, AMF biomass and diversity based on a 29-year fertilization experiment (including control, mineral fertilization, manuring and straw returning treatments). Results showed that GRSP contents increased over years across fertilization treatments. Compared with no fertilization, long-term manuring and straw returning significantly increased bulk soil GRSP by 100% and 80%, respectively, and altered the chemical composition of GRSP by increasing the recalcitrant (aromatic) C proportion. The proportion of aromatic C in GRSP was positively correlated with AMF biomass and diversity (Shannon and Chao1), indicating that the chemical composition of GRSP could be regulated by AMF community and diversity. Moreover, manuring facilitated the formation of macro-aggregates (>250 mu m), thus increasing the physical protection of GRSP. The structural equation modeling further demonstrated that GRSP content was positively regulated by soil macroaggregates, AMF biomass and diversity and their linkage with GRSP chemical composition. Collectively, longterm manuring could facilitate GRSP accumulation by shifts in AMF-mediated GRSP chemical composition (aromatic C) along with enhanced protection of macro-aggregates. This study highlights a feasible way forward for soil quality improvement and carbon sequestration for sustainable agriculture.