Inorganic amendment can delay the degradation of organic amendment by enhancing its resistance and mitigating microbial activities in saline–alkali soils

Soil organic matter (SOM) plays a crucial part in improving soil quality, promoting soil microbial activities, and buffering salt stress, in saline-alkali region. Organic amendment effectively improves the quality and C storage in saline-alkali soil, while it still remains tenuous that how can inorganic amendment affects SOM composition and microbial characteristics when applying organic amendment. An 800-day incubation experiment in saline-alkali soil were conducted with treatment of organic amendment (furfural residue) and a mixture of organic amendment and inorganic amendment (furfural residue and mineral amendment, 4:1). Our results showed that adding mineral amendment based on furfural residue 1) increased the contents of particulate organic carbon, total lignin phenol, cellulose, humic acid (HA), HA-C, and silt-clay-C by 17.64 %, 20.28 %, 168.32 %, 27.62 %, 28.15 % respectively; 2) improved the aromaticity of solid-state SOM and HA, reduced the potential transformation of HA (especially lignin-like compounds), and increased newly generated lignin-like and condensed aromatic-like compounds in HA; 3) reduced microbial biomass and necromass C respectively by 40.08 % and 15.58 %, changing C-degrading enzyme activities and bacterial communities. These findings indicated that extra additive inorganic amendment can reserve plant-derived C and slow microbial-derived C formation by mitigating microbial activities and protecting degradation reactants and products in HA (especially lignin-like and condensed aromatic-like compounds). This study provides direct experimental evidence for the sustainable development of inorganic amendments in the remediation work of saline-alkali soil.