The use of fertilizers is mainly adopted in arid regions to improve the soil carbon (C) pool and crop productivity. However, the mechanisms underlying improvements in dryland wheat field soils related to microbial metabolic activity and community structure remain poorly understood. Therefore, a field experiment with four fertilization treatments and no fertilizer as the control (CK) was conducted for 10 years in a semi-arid region of China. The results revealed that the combined application of chemical and organic fertilizers (fermented chicken manure) clearly increased the levels of soil organic carbon (SOC), dissolved organic carbon (DOC), and light-fraction organic carbon (LFOC) by 13.54–16.72%, 6.96–9.01%, and 11.00–13.51%, respectively, compared to the sole use of chemical fertilizers (FP treatment). Moreover, the combined treatment not only enhanced the metabolic activity of microorganisms concerning carbon source utilization but also increased the diversity of the bacterial community. This caused noticeable changes in the composition of the bacterial community. A Mantel test analysis revealed that Bacteroidetes and Mortierellomycota significantly enhanced the metabolic activity associated with carbohydrate, amino acid, and carboxylic acid C sources. Actinobacteria, Bacteroidetes, and Mortierellomycota facilitated the accumulation of active C and particulate organic carbon (POC), whereas Mortierellomycota specifically promoted the accumulation of heavy-fraction organic carbon (HFOC), thereby collectively influencing the SOC content. The combined application of chemical and organic fertilizers increased the abundance of Bacteroidetes and Mortierellomycota. This enhancement improved the metabolic utilization of carbohydrates, amino acids, and carboxylic acids, resulting in alterations in the types and quantities of soil metabolites. Consequently, these alterations ultimately affect the composition and quantity of the SOC pool in arid agroecosystems. In conclusion, the combined application of balanced NPK fertilizers and organic fertilizers has a strong positive effect in improving soil microbial activity and the soil C pool.

Fertilization alters crop yield, soil aggregation, and carbon sequestration potential. However, the specific effects and interactive mechanisms of long-term fertilization on soil organic carbon (SOC), aggregate-associated organic carbon (OC), and yield in dryland wheat fields remain poorly understood. Therefore, a field experiment with local farmer fertilization (NP), measured and controlled fertilization (NPK), chemical fertilizer plus organic fertilizer (NPKM), chemical fertilizer plus bio-organic fertilizer (NPKB), and no fertilizer (CK) was conducted for 10 years in a semi-arid region of China. We examined the characteristics of crop yield, SOC stock, and soil aggregate under different fertilization methods to explore the carbon sequestration mechanisms associated with increased yield. The results revealed a significant positive linear correlation between carbon sequestration and carbon input, with a carbon sequestration efficiency of 27.4%. Different fertilization treatments increased the proportion of macroaggregates (>0.25 mm) and significantly improved the water stability of soil aggregates, with the combined application of organic–inorganic fertilizers (NPKM and NPKB treatments) showing the most pronounced effect. A redundancy analysis revealed that carbon input was the most important factor affecting aggregate stability. Partial least squares path modeling revealed that SOC content was enhanced primarily because of the increase in macroaggregate-associated OC and carbon input, which in turn led to higher wheat yields. Our findings indicate that macroaggregate-associated OC and carbon inputs have significant implications for SOC sequestration in dryland fields. Thus, we suggest the integrated application of organic fertilizers with balanced NPK fertilizers to promote SOC accumulation, improve aggregate stability, and enhance crop yield.

The Yellow River Basin (YRB) is an important ecological security barrier in China, playing an irreplaceable role in soil and water conservation, climate regulation, and biodiversity maintenance, and it is related to the stability and security of the ecosystem. Exploring the spatial correlation networks and factors influencing ecological security in the YRB can provide new ideas for cross-domain collaborative governance, promote efficient cooperation among regions, and optimize resource allocation. Using a quantitative approach to assess the YRB’s ecological security, we employed an adjusted gravity model, social network analysis, and quadratic assignment procedure analysis to understand the spatial connection dynamics. The results indicate the following: (1) Ecological security in the YRB continued to improve from 2005 to 2019, but the overall level was low. The degree of the dispersion of the ecological security status among cities constantly increased, and there were significant regional differences in the level of ecological security in the YRB. (2) From 2005 to 2019, the number and density of network connections among cities within the YRB increased significantly, and the ecological security links gradually strengthened. The Shandong Peninsula city cluster and the Hubao–Eyu City cluster are not only located at the core of the network but also play the role of “bridge intermediary”, exhibiting strong control. (3) Among all variables, economic development and geographic proximity increased significantly in terms of their correlation with the YRB’s ecological security. The study of spatial connectivity networks and their influencing factors in the YRB provides new ideas for inter-regional collaborative governance.