Engineering Rhizobium Strains for Enhanced Nitrogen Fixation in Soybean

Soybean ( Glycine max ) is an important food and oil crop with a high demand for nitrogen. Long-term reliance on chemical nitrogen fertilizers not only raises production costs but also causes environmental pollution. To address this problem, several engineered rhizobium strains with strong nitrogen-fixing capacity, good stress tolerance, and plant growth-promoting ability were obtained through genetic modification and selection. Field trials were conducted in temperate, subtropical, and semi-arid climate zones, and in various soil types including acidic soil, gray terrace soil, loam, and sandy loam. The results showed that these strains could stably attach to soybean roots and form many effective nodules, maintaining high nitrogen fixation even under adverse conditions such as high temperature, drought, and low pH. Data from the trials indicated that inoculated soybeans yielded 15%~40% more than controls, and even with a 50% reduction in nitrogen fertilizer, high yield and good quality were maintained; seed protein and oil content also increased. In some trials, co-inoculation with phosphate-solubilizing bacteria further reduced nitrogen and phosphorus fertilizer use. Farmers involved in the trials generally found the technology easy to apply and economically beneficial. The study suggests that promoting these rhizobium inoculants can help reduce fertilizer use, lower environmental pressure, and improve the efficiency and sustainability of soybean production.