Biofertilizers – Introduction, Meaning and Concept
The increasing population puts considerable pressure on land and other natural resources of the country causing damage to the ecological base of agriculture and serious socio-economic problems. The increased crop production over years has accelerated the removal of plant nutrient four times during the last four decades putting four fold pressure on soil resources. The replenishment of nutrients lost in crop removal through the use of chemical inputs is not considerable advisable as their use on a long run has been found to decelerate the biological activities in the soil causing impaired soil health, consequently, increasing awareness is being created in favour of adopting biological routes of soil fertility management for preventing soil degradation and for sustaining optimum crop production. In this context, the production and use of Biofertilizers in agricultures assume considerable importance.
Biofertilizers or microbial inoculants can be generally defined as preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilising or cellulolytic microorganisms used for application to seed, soil or composting areas with the objective of increasing the extent of the availability of nutrient in a from which can be easily assimilated by plants.
Microorganism induce many biochemical transformation in soil. These include mineralisation of organically bound forms of nutrients, exchange reactions, fixation of atmospheric nitrogen and various other changes leading to better availability of nutrients already present in the soil. The group of microorganism responsible for nitrogen fixation, phosphate solubilisation and compost decomposition are being put to beneficial use in the form of Biofertilizers.
Biological nitrogen fixation contributes maximum ( 67.5%) towards enriching earth surface with nitrogen. Microorganism capable of assimilating nitrogen are marked with “ nif” genes. They synthesise nitrogenase enzyme responsible for converting otherwise inert N2 to plant usable NH3. Such common useful organism are Rhizobium, Azatobacter, Azospirillium and Blue Green Algae ( BGA). There are some microorganisms capable of solubilising insoluble soil phosphours while some collect available phosphorous from remote places out of reach of plant root hairs by sending elongated filaments. E.g. Vesicular Arbuscular Mycorrhiza. Few of the heterotropic organisms decompose cellulose rapidly. Such beneficial organisms are domesticated in suitable carriers which on application to soil augment crop growth and yield. These carrier based microorganisms are called Biofertilizers or appropriately called bioinoculants or microbial inoculants or microbial fertilizers.