Rhyzobium (RHZ): These inoculants are known for their ability to fix atmospheric nitrogen in symbiotic association with plants forming nodules in roots (stem nodules in sesabaniamrostrata).RHZ are however limited by their specificity and only certain legumes are benefited from this symbiosis.
Azotobacter (AZT): This has been found beneficial to a wide array of crops covering cereals,millets, vegetables, cotton and sugarcane. It is free living and non-symbiotic nitrogen fixing organism that also produces certain substances good for the growth of plants and antibodies that suppress many root pathogens.
Azospirillum (AZS): This is also a nitrogen-fixing micro organism beneficial for non-leguminous plants. Like AZT, the benefits transcend nitrogen enrichment through production of growth promoting substances.
Phosphate solubilizing micro-organisms (PSM) are a group of microbes capable of solubilizing inorganic phosphorus from insoluble sources. In alkaline and acidic soils, the availability to phosphorus is low.
These microbes can be useful to reverse this process. PSM when used with rock phosphate can save about 50% of the crop requirement of phosphatic fertilizer like single super phosphate.
Acetobacter is an obligatory aerobic, nitrogen-fixing bacteria that is known for producing acid as a result of metabolic processes. While all nitrogen-fixing bacteria contain nitrogenase in order to utilize atmospheric nitrogen gas as a source for metabolic biosynthesis, different nitrogen-fixing microorganisms protect the oxygen-sensitive micro-organisms from oxygen exposure in different ways. Acetobactor is useful in sugar cane production.