Aiming at the problems of serious soil desertification, increased soil and water loss, and reduced soil-available nutrients in the agro-pastoral ecotone in Northeast Inner Mongolia, this study took corn variety A6565 as the planting crop and analyzed seven different tillage measures, deep tillage, deep loosening, shallow tillage, rotary tillage, heavy harrow, no-tillage, and control, combined with straw returning at an experimental field in Arong Banner. The analysis results are as follows: the urease activity and microbial biomass nitrogen content of the tillage method combined with straw-returning treatment were higher than other treatments. Compared with the seedling stage, the alpha diversity index of bacteria increased in the harvest stage, while that of fungi was the opposite. β diversity comparison showed that sampling time was the main factor affecting the bacterial community and composition. It was found that the dominant bacteria were Proteobacteria and Actinomycetes, and the dominant fungus was Ascomycetes. Conservation tillage combined with straw-returning treatment has a positive impact on soil microbial diversity, which is more helpful for improving soil-available nutrients and soil quality. All the findings in this study may contribute to restricting a series of important factors affecting sustainable agricultural development, such as soil degradation.

Tillage practices can disrupt soil surface, creating loose, erodible soil layers. This significantly impacts soil organic carbon (SOC) fractions, including microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), readily oxidizable organic carbon (ROC), and heavy fraction organic carbon (HFOC). SOC fractions may depend on soil aggregate size. However, the variation patterns of SOC fractions under different soil aggregate sizes and tillage practices remain unclear. The objectives of this study were to assess the impact of tillage practices on SOC fractions (MBC, DOC, POC, ROC, and HFOC) within soil aggregates and to quantify the relationship between aggregate size and these SOC fractions. Seven treatment combinations were selected: two conventional tillage practices of rotary tillage (RTS) and plow-tillage (PTS) with 100% harvest maize stover mulching, and five conservation tillage practices of subsoiling+100% mulching (STS), no-tillage+30% (NTS1) and 100% (NTS2) mulching, and no-tillage & ridging+30% (NTSR1) and 60% (NTSR2) mulching. Results showed that tillage practices significantly impacted SOC fractions and maize yield (P < 0.05). Specifically, conservation tillage outperformed conventional tillage in enhancing SOC and its labile labile organic carbon (LOC, including MBC, DOC, POC, ROC) by retaining crop residues, increasing carbon inputs, and reducing mechanical disturbance. Mineral-associated organic carbon (MAOC) and heavy fraction organic carbon (HFOC) are classified as stable SOC fractions, and conservation tillage also promoted the accumulation of stable SOC. NTS2 was optimal for SOC accumulation in the 0-20 cm soil layer. STS promoted root carbon input in the 20-40 cm soil layer. Maize yield was the highest under STS and the lowest under RTS. Particularly, ROC (2 mm, 2-0.25 mm) remarkably affected maize yield. Overall, this study demonstrates that the STS treatment can provide an optimal pathway for achieving both high SOC sequestration and maize yield. Future research should further elucidate the coupling mechanism between microbial functional redundancy and carbon turnover dynamics under long-term tillage practices to provide theoretical support for precision agricultural management.

Protein content (PC) stability is crucial for wheat quality. This study utilized partial least squares regression and structural equation modeling to distinguish the physiological effects of “thermal intensity” versus “thermal accumulation” on spring wheat PC across Inner Mongolia. Environmental factors were the dominant drivers of variation. Notably, the Erguna region achieved the highest PC (18.53%) despite recording the lowest total growing degree days. Structural equation modeling analysis revealed that thermal intensity during heading-to-anthesis exerted a strong positive effect on PC (path coefficient = 0.965), likely by enhancing nitrogen remobilization kinetics. Conversely, excessive thermal accumulation and sunshine duration during grain filling negatively impacted PC via a carbohydrate-driven “dilution effect”. These findings suggest that superior PC formation requires a specific spatiotemporal coupling: high thermal intensity prior to anthesis to prime nitrogen transport, combined with low thermal accumulation post-anthesis to restrict carbon dilution. This study provides a physiological basis for optimizing wheat quality zoning by decoupling heat magnitude from duration under future climate scenarios.