Symbiotic Nitrogen Fixers the Rhizobia spp.
Rhizobia (gram negative soil bacteria) are able to enter into symbiotic relationship with legumes (pulses, etc). They fix atmospheric nitrogen and thus not only increases the production in the inoculated crops, but also leave a fair amount of inoculated crops, but also leave a fair amount of  nitrogen in the soil, which benefits the subsequent crop. Following seven groups of Rhizobia have been recognised for inoculating legumes in India : R. leguminosarum, R melilotii, R trifoli, R. phaseoli, R. lupinii, R, japonicum, and Rhizobium spp. The nitrogen fixing ability of legumes inoculated with these rhizobia ranges from 50 kg to 150 kg per hectare. Following efforts are also being made : to increase this ability to fix nitrogen, (i) Efficient rhizobia for different crops and locations, which are tolerant to various stresses (drought, temperature, and high or low pH), are being isolated, maintained and used. (ii) A hup+ gene (uptake hydrogenase) is used, which helps in recycling of H2 produced during nitrogen fixation.

The demand for rhizobia in India during the seventh plan (@ 500g per ha) was estimated to be 7,150 tonnes. However, against a capacity of 2,150 tonnes, only 627.2 tonnes of Rhizobia was being produced towards the end of 1988.

Capacity and present production of Rhizobia culture in India