Biofertilizers – A Key to Sustaining Agricultural Productivity: A Review

Abstract:

The application of mineral fertilizers is the most advantageous and the fastest way to increase crop yields. In the last few decades, the rate of Nitrogen (N), phosphorous (P), and potassium (K) or NPK fertilizer application has tremendously increased in crop production. The excessive use of synthetic agrochemicals in crop production and in soil fertility management causes residue toxicity and environmental pollution. This is due to the low use efficiency of externally applied fertilizers by the plants, long-term application, leaching, and evaporation to the atmosphere. Therefore, the reduced use of synthetic agrochemicals in crop production and maintaining soil fertility by alternative means is the subject of investigation. The challenge is to continue sustainable agricultural crop production through minimization of the harmful effect of fertilization. Among the different alternatives, researchers hypothesized that bio fertilizers could be a substitute for these. The term bio fertilizers or 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 cellulolytic microorganisms. Bio fertilizer, also known as a living fertilizer, is composed of microbial inoculants or groups of microorganisms which are able to fix atmospheric Nitrogen, the microorganisms are known as biological nitrogen fixers. They are grouped into free-living bacteria (Azotobacter and Azospirillium), Blue-green algae, and symbionts such as Rhizobium, Frankia, and Azolla. They are used for application on seed, in soil, or composting areas with the objective of increasing the numbers of such microorganisms and accelerate certain microbial processes. These, in turn, augment the extent of the availability of nutrients in a form that can be easily assimilated by plant. In the larger sense, the term may be used to include all organic resources (manure) for plant growth which are rendered in an available form for plant absorption through microorganisms or plant associations or interactions of 0.050. According to an estimate, 240 million tons of food grains will be required to feed about 1 billion expected populations by 2000 A.D. in India, and to achieve this milestone, a sizable quantity of mineral fertilizers will be required. The total fertilizer requirements of our country would be 23 million tons as against the present consumption level of 13 million tons per annum. The problem is so acute that it is beyond any single type of nutrient source to accept the challenge of an appropriate nutrient supply. Integrated use of all the seeds, such as mineral fertilizers, organic manures, bio-fertilizers, etc., is the only alternative for improving soil fertility. The use of organic manures and mineral fertilizers is in practice, but bio fertilizer in agriculture is not very popular. Hence, there is a need to make its use popular. The increased cost of fertilizer production, coupled with progressively increasing use of chemical fertilizers particularly needed by High Yielding Varieties (HYV), are adding to the cost of cultivation of crops and causing a nutritional enhancement in Indian agriculture. The vast gap cannot be filled up merely by producing synthetic nitrogenous fertilizers due to scarcity and the high cost of raw materials such as fossil fuels. Biological nitrogen fixation is the key to sustaining agricultural productivity, and the application of bio fertilizers in the field is a viable alternative