Yield and Seed Quality of Faba Bean ( Vicia faba L. var. minor ) as a Result of Symbiosis with Nitrogen-Fixing Bacteria

Faba bean is a high-protein legume that can be successfully grown in most climates around the world. It is one of the most popular pulses cultivated in Poland. Its seeds are a source of plant protein, used most often in feed production. Field experiments and laboratory seed analyses were carried out in 2022 and 2023 to assess the effect of the application of nitrogen-fixing bacteria on the yield and seed quality of a low-tannin faba bean cultivar. The factor was tested at four levels: control, seed inoculation with Rhizobium leguminosarum bv. viceae , foliar spraying with Methylobacterium symbioticum , and seed inoculation and spraying (double application). The application of N-fixing bacteria had a positive effect on faba bean seed yield. In 2022, plants responded most effectively to a double application, increasing seed yield by 25.4%, while, in 2023, the highest seed yield was obtained after inoculation (12.3% increase). Although the single application of bacteria caused a decrease in seed protein content, the double application (inoculation and spraying) significantly enhanced seed protein content. The protein productivity per hectare was compensated by the higher seed yield and increased by 41.7% in 2022 and 14.9% in 2023 compared to plots where N-fixing bacteria were not applied. This work shows that it is possible to use different strains of N-fixing bacteria in faba bean cultivation and this can significantly improve yields while reducing the need for synthetic nitrogen fertilizers, which supports sustainable production.