The microorganism which can fix atmospheric nitrogen in the soil is bacteria. Several species of bacteria are capable of fixing nitrogen, but the most widely known species are Acetobacter and Rhizobium.
- Nitrogen fixation has also observed between termites and fungi. In addition, some of these nitrogen-fixing bacteria form symbiotic relationships with plants, more specifically, legumes.
Rhizobium is the bacteria that live in symbiotic association with the root nodules of the leguminous plants. Fixation of nitrogen cannot be done independently. That is why rhizobium requires a plant host. Rhizobium is a vital source of nitrogen to agricultural soils, including those in arid regions.
Few species of Rhizobium bacteria include:
- Rhizobium leguminosarum
- Rhizobium alamii
- Rhizobium lantis
- Rhizobium japonicum
- Rhizobium trifolii
- Rhizobium phaseolii
- Rhizobium smilacinae
Specific strains of Rhizobium are required to make the nodules functional to carry out the process. This increases the yield of the crops. Legume inoculation has been an agricultural practice for several years and has constantly improved over time.