Bio fertilizers : Use and importance

Nitin Kumar Pandey
Indian economy is based on agriculture. Agriculture plays a vital role in Indian GDP Indian agriculture has seen major technological advances since late 1960s and has succeeded in enhancing food production and in achieving self-sufficiency. The introduction of high yielding varieties of seed and the increased use of fertilizers and irrigation followed by the pest control measure in a later parts lead to green revolution in Indian agriculture. The total fertilizers requirements in India would be 24 million tones, and against the present consumption level of 14 million tones. Which is beyond any single type of nutrient source to accept the challenge of appropriate nutrient supply. Integrated use of all the sources such as mineral, fertilizers, organic manures, biofertilizers etc. are the only alternate for improving soil fertility.
India is fourth largest user of chemical fertilizers in the world. The strategy for sustaining satisfactory yield levels envisage nutrient balance and efficient nutrient cycling. This can be achieved through integrated use of mineral, fertilizers, compost, organic manures, green manure, and biological inoculants etc. However, such indiscriminate use of chemical fertilizers also led to environmental pollution, erosion of soil quality and contamination of farm produce and ground water by chemical fertilizers residues and consequent health hazards. Chemical fertilizers have affected the environment through nitrate poisoning and experimentation of beneficial micro flora and micro fauna by adversely affecting the physical and chemical structure of the soil. It has been observed that the concentration of chemicals in ground water has reached levels, which are hazardous to human, and live stock population. Post green revolution has experienced continuous decline in food grain production against consumption of NPK. The NPK consumption in India is above the world average consumption, however the average yield per hectare is much below the world average.
The term bio fertilizers or which can be more appropriately called ‘microbial inoculants’ can be generally defined as a preparation containing live or latent cells of efficient strains of nitrogen fixing, Phosphate solubilizing or cellulytic microorganisms used for application of seed, soil or composting areas with the objective of increasing the number of such microorganisms and accelerated certain microbial process to argument the extent of the availability of nutrients in a form which can be easily assimilated by plant. In large sense, the term may be used to include all organic resource for plant growth, which are rendered in an available form for plant absorption through micro organisms or plant associations.
The potentials of biofertilizers for promoting sustainable agriculture have been known for many years. “Microbial inoculants” or culture is the most appropriate name of biofertilizers.
Important microorganisms used as biofertilizers-
Blue Green Algae (BGA)- It is most common species are Anabaena and Nostoc. It can be grow in temperature range of 25 to 450C. Standing water of 2-10 cm in the field is prerequisite for its growth. It fix about 20-45 kg nitrogen per hectare. It grow well in pH 7-8 and soil high in organic matter.
Rhizobium- This is a soil bacterium that fix nitrogen after becoming established inside root nodules of legumes characterized by their unique ability to infect root hairs of legumes and induce effective N2-fixing nodules to form on the roots.
They are rod shaped living plants which exist only in the vegetative growth stage. Unlike many other soil microorganisms’ rhizobia produce no spores and they are aerobic and motile. Symbiotically it fix nitrogen 50-100 kg/ha with legumes like chickpea red gram, pea, lentil, green gram, etc. Oil seed legumes like soya bean and ground nut and forage legumes like berseem and Lucerne.
Azotobacter- Azotobacter is free living aerobic nitrogen-fixing bacteria, which can substitute part of inorganic fertilizers.
(To be contd)