Introduction to Biofertilizers
Biofertilizers are microbial inoculants or carrier based preparations containing living or latent cells of efficient strains of nitrogen fixing, phosphate is solublizing and cellulose decomposing microorganisms intended for seed or soil application and designed to improve soil fertility and plant growth by increasing the number and biological activity of beneficial microorganisms in the soil.
The objects behind the application of Biofertilizers /microbial inoculants to seed, soil or compost pit is to increase the number and biological / metabolic activity of useful microorganisms that accelerate certain microbial processes to augment the extent of availability of nutrients in the available forms which can be easily assimilated by plants. The need for the use of Biofertilizers has arisen primarily due to two reasons i.e. though chemical fertilizers increase soil fertility, crop productivity and production, but increased / intensive use of chemical fertilizers has caused serious concern of soil texture, soil fertility and other environmental problems, use of Biofertilizers is both economical as well as environment friendly. Therefore, an integrated approach of applying both chemical fertilizers and Biofertilizers is the best way of integrated nutrient supply in agriculture.
Organic fertilizers (manure, compost, vermicompost) are also considered as Biofertilizers, which are rendered in available forms due to the interactions of microorganisms or their association with plants. Biofertilizers, thus include i) Symbiotic nitrogen fixers Rhizobium sp. ii) Non-symbiotic, free living nitrogen fixers Azotobacter, Azospirillum etc. iii) BGA-inoculants Azolla-Anabaena, iv) Phosphate solubilizing microorganisms (PSM) Bacillus Pseudomonas, Penicillium Aspergillus etc. v) Mycorrhiza vi) Cellulolytic microorganisms and vii) Organic fertilizers.
Nobbe and Hiltner (1895, USA) produced the first Rhizobium biofertilizer under the brand name “Nitragin” for 17 different legumes.