Rhizobia take water and nutrients they need to live from rhizobia cells, which can fix free nitrogen and synthesize nitrogenous compounds. The symbiosis between legumes and rhizobia results in high yields due to the availability of nitrogen; at the same time, due to the shedding of rhizomes, the root system or stumps with rhizomes are left in the soil, which increases the fertility of the soil.

According to the species of symbiotic bacteria in rhizosphere, rhizosphere can be divided into 3 major categories: rhizobial rhizosphere, cyanobacterial rhizosphere, and actinomycete rhizosphere. Rhizobial rhizomas are mainly found in legumes, but also in elms; cyanobacterial rhizomas are found in very few plants such as Stachybotrys; and actinomycete rhizomas are mainly found in woody plants.

Rhizobia, scientific name Rhizobiaceae, is a collective name for microorganisms of the phylum Aspergillus, order Rhizobia, family Rhizobiaceae. Rhizobia is a group of rod-shaped bacteria that live in symbiosis with legumes, forming root nodules and fixing nitrogen in the air for plant nutrition. They are Gram-negative symbiotic nitrogen-fixing bacteria with irregular shapes, and the isolated bodies from rhizobia are also called bacteroid. Rhizobacteria can not fix nitrogen when they are free in the soil, but only when they form rhizobia with legumes can they fix nitrogen. Rhizobia have specificity, such as soybean rhizobia can only be symbiotic with soybeans, peanut rhizobia can only be symbiotic with peanuts. It can convert the nitrogen in the air into ammonia, and in addition to its own needs, its excess can be absorbed by plants. The rhizobacterial agent is low cost, good effect, no pollution, it is worth to promote the use of “green fertilizer”.