Molecular Soil Biology 2025, Vol.16, No.4, 188-198 http://bioscipublisher.com/index.php/msb 1 95 rhizobia in major soybean producing areas in the world. Through continuous innovation and scientific management, engineered rhizobia is expected to become the key biotechnology to promote the green revolution in agriculture and cope with the global nitrogen crisis (Thuita et al., 2011; Abd-Alla et al., 2023; Kolapo et al., 2025). 6 Case Study 6.1 Pilot field trials in different soil types and climate zones Pilot-scale field trials were conducted to assess the field performance of engineered rhizobium strains across a range of soil types (acidic soil, gray terrace soil, loam, and sandy loam) and climate zones (temperate, subtropical, and semi-arid). A randomized block design was used at each location with three treatments: engineered strain inoculation, a commercial inoculant, and a non-inoculated control. Local main soybean varieties were planted at each site. In some locations, engineered strains were co-applied with plant growth–promoting and phosphate-solubilizing bacteria to evaluate synergistic effects (Alam et al., 2015; Igiehon et al., 2019; Shome et al., 2022). In the field experiments in different ecological areas, the engineered Rhizobium strains can stably colonize in soybean roots and induce a large number of effective root nodules. Especially under the conditions of high temperature, drought and low pH, the engineered strains showed stronger environmental adaptability and nodulation ability. For example, in semi-arid areas and acid soils, engineered strains R1 and R3 not only increased the germination rate of soybean seeds, but also significantly increased the number of nodules and nitrogenase activity (Igiehon et al., 2019). In the environment of high nitrate nitrogen, some new strains can still maintain efficient nitrogen fixation, breaking through the limitation that traditional strains are easily inhibited by nitrogen fertilizer (Nguyen et al., 2019). 6.2 Yield gains and reduced nitrogen input The effects of engineered Rhizobium strains on soybean yield and nitrogen input were systematically evaluated in field experiments. The yield of soybean inoculated with engineered strains was significantly higher than that of non inoculated and conventional inoculated groups, with an increase of 15%~40%, and even higher in some regions (Alam et al., 2015; Shome et al., 2022). In the low fertility soils such as gray platform soil and loam soil, the yield increasing effect of engineering strains is particularly prominent. The increase in yield was mainly attributed to the increase in nodule number and nitrogenase activity, which promoted nitrogen accumulation and protein synthesis in Soybean (Alam et al., 2015). The protein content and oil content of soybean seeds in the engineered strain group also increased to varying degrees, and the quality advantage was obvious (Shome et al., 2022). Use of these strains also made it possible to reduce chemical nitrogen fertilizer application. Data from several sites indicated that when nitrogen fertilizer use was cut by half, the engineered strain treatments still matched or exceeded the yields and quality of the full-fertilizer control (Damanhuri et al., 2020; Shome et al., 2022; Abd-Alla et al., 2023) (Figure 2). When co-inoculated with phosphate-solubilizing bacteria, soil nitrogen and phosphorus availability improved further, allowing reductions in both nitrogen and phosphorus fertilizer inputs without yield loss (Shome et al., 2022). 6.3 Farmer feedback and adoption potential On the basis of field experiments, the research team conducted a systematic return visit and questionnaire survey to the participating farmers, and collected farmers' feedback on the application effect, operation convenience and economic benefits of engineered Rhizobium strains. Most farmers reported that after the inoculation of the engineered strain, soybean grew more vigorously, had more nodules, and the yield and quality were improved, especially under drought, barren or high temperature and other adverse conditions (Alam et al., 2015; Igiehon et al., 2019; Shome et al., 2022). Some farmers also noted that the demand for nitrogen fertilizer in soybeans after inoculation with engineered strains decreased significantly, which saved production costs and improved economic benefits (Abd-Alla et al., 2023; Kolapo et al., 2025). In terms of willingness to popularize and apply, farmers generally expressed their willingness to continue to use
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