Combined Inoculation of Rhizobium and Nitrogen Fertiliser Application on Nitrogen Fixation in Soybean (Glycine max L.) at Central Vietnam

The use of soybeans (Glycine max L.) as a food and animal feed has grown dramatically throughout Vietnam in recent years. Relatively few studies have examined the relationships between rhizobium inoculation and nitrogen application on soybeans in Central Vietnam. The study aimed to evaluate the responses of rhizobium inoculation and split N fertiliser application on nodule and N₂ fixation in coastal sandy soil at Hue city, Central Vietnam.

Field experiments were conducted in coastal sandy soil in two cropping seasons of 2025. Six treatments with two factors including split times of N fertiliser application in combination with and without inoculation of rhizobium which were laid out in a split plot design with three replications. Data was collected as nodule number, fresh and dry weight and nitrogen fixation efficiency.

The obtained results showed significant differences (p<0.05) in nodules characteristics, N uptake and N fixation between inoculated and no inoculated treatments combined with split times of N fertiliser application. The three times of N fertiliser application and rhizobium inoculation was shown the best in all parameters. Further study will be considered on how the N₂ fixation related with soybean yield and N use efficiency.