Describe the role of rhizobium in maintaining soil fertility?

Rhizobium is a nitrogen-fixing bacterium that is able to convert atmospheric nitrogen into nitrates. Nitrogen is an important plant nutrient which is required to make proteins. Rhizobium bacteria live in a symbiotic association within the roots of leguminous plants (pea, pulses, gram, and beans). Rhizobium essentially requires a plant host as it cannot fix nitrogen in its free form. It converts atmospheric nitrogen into absorbable form (nitrates) as the plants are unable to take up and utilise atmospheric nitrogen. The role of rhizobium is highly significant in maintaining soil fertility as the soil never runs deficient in nitrogen and the growing plants remain disease-free.