Molecular Soil Biology 2025, Vol.16, No.5, 272-286 http://bioscipublisher.com/index.php/msb 276 response to the problem of nutrient imbalance, soil testing and formula fertilization should be implemented to replenish the deficient nutrients in time and avoid excessive fertilization to maintain the dynamic balance of soil nutrients (Ren et al., 2022). The stress of salinized soil on the growth of legume crops should not be ignored. Excessive salt can cause osmotic stress and ion toxicity, reduce the germination rate of legume seeds and the survival rate of seedlings, make the plants short, and the leaves turn yellow. In severe cases, no grains can be harvested. A field experiment showed that when soybeans were planted on saline-alkali land, the plant height, number of pods, and grain yield were 25%, 26.6%, and 33% lower than those in normal soil, respectively (Ren et al., 2023). Salt-alkali stress can also destroy the living environment of rhizobia, inhibit their infection of legume roots, and thus weaken the nitrogen fixation ability of legumes (de Almeida et al., 2022). To alleviate the harm of salinity, soil salt concentration and exchangeable sodium content can be reduced by adding soil, washing salt and using improvers (such as gypsum) to create a suitable root zone environment. At the same time, breeding salt-tolerant varieties and inoculating salt-tolerant and efficient rhizobia are also effective measures (Gao et al., 2022). In recent years, functional microorganisms that promote plant salt tolerance have received widespread attention. For example, certain Streptomyces can increase the survival and yield of soybeans in soda saline-alkali soils. In response to nutrient imbalance and saline-alkali stress, comprehensive soil improvement and cultivation management methods are needed to ensure that legume crops obtain a balanced nutrient supply and a suitable rhizosphere environment to achieve normal growth and development. 4 Targeted Soil Management Measures 4.1 Tillage methods to improve soil structure Good soil structure is the basis for high yields of legume crops. For soils with poor structure, the tillage method can be adjusted to improve it. For heavy and compacted soils, deep plowing and deep loosening are one of the common measures. By increasing the tillage depth (such as >25 cm) and breaking the plow bottom layer, the soil bulk density can be significantly reduced, the macroporosity can be increased, and thus the ventilation and water permeability can be improved (Wang et al., 2020). Experiments in the Huanghuaihai Plain have shown that compared with traditional plowing, deep loosening rotation can reduce the soil density of the 0 cm-20 cm soil layer by about 0.1 g/cm³, increase the root depth of soybeans by 15%, and increase the final yield by about 8%. No-tillage straw mulching is also an important method of conservation tillage, which is suitable for soils with high organic matter. For example, the promotion of no-tillage mulching technology in the black soil area of Northeast China can reduce soil disturbance and maintain aggregate structure, which can improve soil stability and erosion resistance in the long run. Studies have shown that after 8 years of straw mulching and no-tillage on sloping farmland, the water-stable aggregates of black soil > 0.25 mm increased by more than 10%, the soil infiltration rate increased, and the rainfall utilization efficiency and yield of soybean planting increased. Reasonable crop rotation can also help improve soil structure. The rotation of legumes and grasses can improve the pore distribution of the soil layer by utilizing the root characteristics of different crops. The deep roots of legumes loosen the soil, and the fibrous roots of grasses increase viscosity. Alternating the two can fertilize the soil and increase organic matter (Chalise et al., 2019). For example, the rotation of soybeans and corn not only increases the organic carbon content in soil aggregates, but also reduces the compaction of shallow soil, which is conducive to the rooting of subsequent soybeans (Zhang et al., 2021). Selecting appropriate tillage systems according to soil structure conditions, such as deep ploughing and loosening, no-till mulching, and crop rotation, can significantly improve the physical structure of the soil and create good conditions for the growth of legume roots. 4.2 Soil organic matter improvement strategy and green manure utilization Increasing soil organic matter content is one of the effective ways to enhance soil fertility and stabilize soil structure. To this end, soil organic matter can be continuously supplemented by increasing the application of organic fertilizers, planting green manure crops, and returning straw to the field. Practice has shown that long-term application of organic fertilizers can significantly improve soil carbon and nitrogen conditions and microbial activity, which is beneficial to the nutrient acquisition and yield increase of legume crops (Yao et al., 2020). In a four-year experiment in the dry land of Northwest China, the introduction of legume green manure (such as pea green manure) and wheat rotation not only improved the organic matter and total nitrogen levels of
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