Molecular Soil Biology 2025, Vol.16, No.5, 272-286 http://bioscipublisher.com/index.php/msb 282 and retain fertilizer has been enhanced. The 30-year positioning experiment of Zhang et al. (2021) also showed that under the conditions of long-term organic + inorganic fertilization of black soil and straw return to the field, the wheat-soybean rotation system not only has stable yield, but also achieves continuous accumulation of soil organic carbon pool and reduces net greenhouse gas emissions. It can be seen that in the black soil area, returning straw to the field to maintain soil fertility lays the foundation for high soybean yield. In terms of cultivation management, attention is also paid to reasonable rotation and integrated pest and disease control to avoid continuous cropping obstacles and disease outbreaks. Soybean seedlings suffering from root rot often show browning and rotting of the root system, necrosis of the stem base, wilting and even death of the plant (Figure 2). The promotion of the "soybean-corn-soybean" rotation model breaks the pest and disease cycle and reduces the incidence of soybean root rot by 40% (Liu et al., 2025). The typical model in the Northeast Black Soil Area is to combine soybean high-yield cultivation technology with soil fertilization and improvement. Through returning straw to the field and scientific rotation, a virtuous cycle of "improving soil fertility-increasing yield" is achieved, which provides a demonstration for the protection and utilization of black soil. This experience is also of reference significance to other high-fertility soil areas (such as black brown soil areas). Figure 2 Soybean plants with root rot symptoms in the field (Adopted from Liu et al., 2025) 7.2 Huanghuai region: alkaline soil improvement and microbial synergistic root promotion The soil in some areas of the Huanghuai Plain is alkaline and heavy in texture, and the growth of legume crops is often troubled by problems such as iron deficiency, chlorosis, and poor root development. In response to this situation, local demonstrations of combining soil improvement with biotechnology have been carried out. By applying gypsum to improve alkaline soil, the soil pH and exchangeable sodium content are reduced, creating a soil environment suitable for root growth. After applying 3 tons of phosphogypsum per hectare at a certain test site, the pH of the 0~20 cm soil layer dropped from 8.5 to 7.8, the soil became loose, and the average soybean yield increased by 15% after three years. The introduction of microbial agents to promote root growth, such as inoculating a mixed agent of stress-resistant rhizobia and phosphate-solubilizing bacteria, enables legume root nodules to fix nitrogen smoothly in saline-alkali soil and improves nutrient utilization. The study by de Almeida et al. (2022) proved on saline soil that the simultaneous inoculation of rhizobia and growth-promoting bacteria can significantly reduce the growth inhibition of soybeans under salt damage, increase yield and nitrogen accumulation. In a demonstration in Xinxiang, Henan, a multi-strain bio-organic fertilizer was applied when peanuts were planted in alkaline tidal soil. As a result, the root length and number of nodules of peanuts increased by more than 30% compared with conventional treatment, and the pod yield increased by 12% (Zhang et al., 2023). These effects are due to the production of organic acids, plant hormones and other substances by beneficial microorganisms in the rhizosphere, which promote the release of insoluble nutrients and the expansion of the root system (Abulfaraj and Jalal, 2021). In addition, the Huanghuai region also promotes the drip irrigation and fertilization technology of beans, which improves the soil moisture conditions while accurately supplying nutrients to avoid the secondary salinization of the soil caused by traditional flooding. The case of Huanghuai
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