Years of employing the “one-shot” fertilization practice have led to low nutrient utilization efficiency and the degradation of soil structure in the black soil region during crop cultivation. Replacing a portion of chemical fertilizers with microbial agents can effectively solve these issues. In this study, we conducted a field plot experiment comparing eight different treatment combinations to investigate the effects of combining microbial agents with varying amounts of chemical fertilizers on black soil nutrients, soil ecology, and maize yield. The high-throughput absolute quantification 16S rRNA sequencing method was utilized to further investigate the effect of the various treatments on soil bacterial community structure and elucidate the interactions between environmental factors and microbial communities. The results showed that MC80 increased maize yield by 5.76% compared to RC, with an input–output ratio of 1:1.58. Additionally, soil nutrient levels in MC80 were higher than those in RC, increasing nutrient utilization efficiency, activating soil nutrients, and enhancing soil fertility. Meanwhile, the absolute quantification data of bacteria also indicated the highest bacterial abundance and diversity in MC80 samples. Among these, Acidobacteria was the main contributor to the changes in the bacterial community, showing significant enrichment in MC80. RDA and Spearman correlation analyses indicated that soil nutrients are the key factors influencing the bacterial community in this ecosystem, while the microbial community plays a crucial role in nutrient transformation processes. Principal component analysis (PCA) was used for comprehensive evaluation and ranking. Overall, the soil under the MC80 treatment was most conducive to microbial survival and maize growth. This study provides a high-yield and sustainable fertilization method for maize and offers a theoretical basis for applying microbial agents in sustainable agriculture.

Soil salinization is closely related to land degradation and is presumed to exert a significant effect on the preservation of soil organic carbon (SOC). However, the salinization-induced changes in SOC accumulation over the application gradient of amendments remain unclear. To evaluate the potential for salinization elimination and C sequestration, incubation experiments with four straw addition levels and six aluminum sulfate (Al³⁺) gradients were conducted in a soda saline–alkali soil, followed by the analysis of partial least squares path models (PLS-PM). The results showed that combined applications significantly reduced soil salinity and sodicity. The C sequestration performance under coapplications was greater than that under individual applications. The SOC and heavy fraction OC (HFOC) contents under the coapplication of 1.6% Al³⁺ and 10% straw were greater than those under the individual applications of either 1.6% Al³⁺ or 10% straw by 231.08% and 149.86%, and 9.70% and 18.78%, respectively. Coapplications significantly increased macroaggregates and aggregate-associated SOC levels. PLS-PM demonstrated that Na⁺, Ca²⁺ and HCO₃⁻ were important environmental factors associated with C sequestration. Overall, our results suggest that Al³⁺ and straw enhanced C sequestration by regulating salt ions and increasing soil aggregates and that 10% straw combined with 1.6% Al³⁺ had a greater effect on soda saline–alkali soil. Our study is highly important for the utilization of saline–alkali land and C sequestration in western Jilin Province.

Saline–alkali soils suffer from severe deficiencies in available phosphorus, and externally added phosphorus is readily immobilized by metal ions in the soil. Therefore, activating inorganic phosphorus in the soil represents a significant challenge. In this study, 35 salt–alkali-tolerant bacteria were isolated from rhizosphere soils (pH 9.20–9.68). Three phosphate-solubilizing strains (HA2, HPA5, and KA1) capable of growing under severe saline–alkali stress conditions (pH 10, 5% NaCl) and possessing multiple plant growth-promoting traits (nitrogen fixation, potassium solubilization, siderophore production, and IAA secretion) were screened and co-cultured to form the microbial consortium HHK. It was hypothesized that this consortium might exhibit synergistic effects, resulting in significantly higher phosphorus solubilization capacity compared to individual strains. The results showed that under saline–alkali stress, the phosphate solubilization capacity of HHK (484.59 ± 15.79 mg/L) was significantly higher than that of any single strain (285.59 ± 12.60 mg/L). Non-targeted metabolomics and enzyme assays indicated that HHK solubilizes P via organic acids (e.g., citric, L-malic acid) and synergistically modulates core metabolic pathways, including ABC transport, TCA cycle, and glycolysis, alleviating oxidative damage and maintaining cellular homeostasis. Short-term soil incubation confirmed that HHK significantly increased available phosphorus (53.67%) and soil fertility, indicating its potential as a biofertilizer.

Organo-mineral complexes are intimately involved in protecting the stability of soil organic carbon (SOC), as they are influenced by environmental factors such as pH and redox conditions, as well as by the implementation of appropriate management practices. Nevertheless, the mechanism between environmental factors and the fractions of organo-mineral complexes, as well as their response to tillage practices, remain poorly understood. This study investigated the effects of rotary tillage (RT), plow tillage (PT), and no-tillage (NT) on organo-mineral complexes (water-dispersible G0 fraction, sodium-dispersible G1 fraction, grinding-dispersible G2 fraction) and their organic carbon (OC) in the black soil region of Northeast China in 2002 and 2022. Compared to 2002, the content of organo-mineral complexes and their OC in 2022 increased by 5.54% and 3.15%, respectively. Relative to PT, RT and NT increased the organo-mineral complex content by 0.39% and 8.40%, and increased the OC content by 9.41% and 20.56%, respectively. Between 2002 and 2022, tillage measures led to greater contributions of organo-mineral complexes to soil carbon sequestration. RT and PT primarily enhanced the contribution rate of the G0 fraction, whereas NT resulted in enhanced contribution rates for both the G0 and G1 fractions. This suggests NT is most conducive to transforming SOC into stable organo-mineral complexes. Redundancy and correlation analyses identified exchangeable Ca²⁺ in G1, pH, clay, TP, along with iron and aluminium oxides, as key environmental factors influencing the transformation pathways among the complexes fractions.

Organo-mineral complexes are intimately involved in protecting the stability of soil organic carbon (SOC), as they are influenced by environmental factors such as pH and redox conditions, as well as by the implementation of appropriate management practices. Nevertheless, the influencing factors of organo-mineral complexes, as well as their response to tillage practices, remain poorly understood. This study investigated the effects of rotary tillage (RT), plow tillage (PT), and no tillage (NT) on organo-mineral complexes (water-dispersible G0 fraction, sodium-dispersible G1 fraction, grinding-dispersible G2 fraction) and their organic carbon (OC) in the black soil region of Northeast China in 2002 and 2022. Compared to 2002, the content of organo-mineral complexes and their OC in 2022 increased by 5.54% and 3.15%, respectively. Relative to RT, PT and NT increased the organo-mineral complex content by −0.39% and 7.98% and increased the OC content by −8.60% and 10.19%, respectively. Between 2002 and 2022, tillage measures led to greater contributions (78.71%) of organo-mineral complexes to soil carbon sequestration. In 2022, the NT treatment showed significantly higher exchangeable Ca²⁺ content than both the RT and PT treatments by 17.35% and 24.16%, respectively. Relative to RT, the PT treatment resulted in decreased levels of free and crystalline oxides of iron and aluminum, alongside increased levels of amorphous and complexed forms. By contrast, the NT treatment displayed a reverse trend. Redundancy and correlation analyses identified exchangeable Ca²⁺ in G1, pH, clay, and TP, along with iron and aluminum oxides, as key environmental factors influencing the transformation pathways among the complex fractions.