Rhizobia are naturally occurring soil-borne bacteria, which fix nitrogen in symbiosis with legumes. In beans, an additional inoculation of seeds with such bacteria can increase nitrogen fixation. Rhizobia - based solutions are commercially available and are included in the authorized list of inputs for organic agriculture (https://www.inputs.eu/input-search.html). How to test the positive effect of nitrogen fixation by Rhizobium? Compare the following treatments (T) with each other for the biomass produced, yield of seeds or growth of the plants at a given stage: - T0: plants are not inoculated and not fertilized with nitrogen - T1: plants are not inoculated, but fertilized with nitrogen - T2: plants are inoculated and not fertilized with nitrogen For each treatment, use an individual pot or planting container or make sure to have enough space between the differently treated plants. This will prevent the spread of Rhizobia or nitrogen leakage, which could influence the results.