The mechanisms through which different types of exogenous carbon enhance the soil organic carbon sequestration rate (C_seq), nitrogen use efficiency (NUE), and corn yield (CY) in rainfed farmland on the Loess Plateau remain inadequately elucidated. This study established a four-year fixed-site experiment in the context of organic materials to increase soil organic carbon storage and enhance corn yield in the dry-farmed areas of the mountainous southern Ningxia region. The research investigates the effects of adding different types of exogenous carbon materials on C_seq, NUE, and CY. The soil type at the experimental base is loessial soil (Huangmian soil), with a soil pH of 8.28 and a baseline organic carbon content of 8.20 g kg⁻¹. The main crop cultivated in this area is corn. The experimental treatments were as follows: (i) N, no fertilization; (ii) CK, 100% nitrogen, phosphorus, and potassium fertilizers; (iii) C, 50%CK + corn straw (pulverized); (iv) M, 50%CK + fermented cow manure; (v) C/M, 50%CK + fermented cow manure + corn straw (1:1). The results show that compared with the CK treatment, the C_seq of C, M, and C/M treatments increased by 488.89%, 355.56%, and 527.78%, respectively. Compared with the CK treatment, the NUE of C, M, and C/M treatments increased by 15.04%, 7.70%, and 12.20%, respectively. Compared with the CK treatment, the CY under the C, M, and C/M treatments were increased by 7.91%, 19.10%, and 11.59%, respectively. The linear regression results show that the C_seq had a significant positive effect on CY (R² = 0.37) and NUE, R² = 0.39) (p < 0.0001). The TOPSIS (technique for order preference by similarity to ideal solution) evaluation results indicate that the C/M treatment was the optimal measure for achieving increased corn yield while enhancing Cseq and NUE. Therefore, incorporating a 1:1 mixture of corn straw and cattle manure in rainfed farmland in the mountainous area of southern Ningxia may be the best strategy to improve C_seq and NUE.

Irrigation-silted soil in Ningxia represents a unique, anthropogenically modified agroecosystem, beneficial for regional food security. Yet, how different agricultural management techniques influence soil microbiome diversity remains poorly explored. Full-length amplicon sequencing (16S rRNA and ITS) was applied to assess the effects of vegetable and maize cultivation, relative to an uncultivated wasteland control, on soil bacterial and fungal community. Cropping patterns significantly influenced microbial alpha diversity, with contrasting effects on bacterial and fungal communities. Specifically, bacterial diversity peaked in vegetable fields, while fungal diversity was highest in maize fields. Both the bacterial and fungal community structures differed markedly among the three land-use types (p < 0.01). Although Pseudomonadota (among bacteria) and Ascomycota (among fungi) were the dominant phyla across all soils, each land-use type harbored distinct biomarkers. For example, vegetable fields facilitated the enrichment of the genus Fusarium, whereas maize fields were characterized by both Pseudomonadota and diverse saprotrophic fungi. Based on functional prediction, sulfur oxidation and cellulose decomposition were enhanced in soil with vegetable cultivation, while maize cultivation promoted relatively broader metabolic activity and enriched arbuscular mycorrhizal fungi compared with the control. Agricultural practices act as selective filters shaping soil microbial assembly and function, which provide a theoretical foundation for sustainable management strategies aimed at preserving soil health.