Biofertilizers: Yesterday, Today and Tomorrow

Abstract

India, being an agriculture-based country, there has always been a concern about crop improvement here. Chemical fertilizers increased crops yield, but eventually leached out soil, polluted water basins, degraded ecosystems, reducing soil fertility and thus causing damage to overall environment. Organic fertilizers are costlier and they released nutrients in the surrounding environment thus degrading soil and water quality and human health. Thus came into picture the use of GM crops which have beneficial effects but their prevalent usage has ethical concerns and controversies. In the development and implementation of sustainable agriculture techniques, biofertilization (an alternative to mineral fertilizers) is of great importance in order to alleviate deterioration of natural and environmental pollution. Bacterial inoculants that help in plant growth are generally considered to be of two types: (a) symbiotic and (b) free living. Beneficial free-living bacteria referred to as PGPR are found in the rhizosphere of the roots of many different plants. PGPR are free-living, soil-borne bacteria that colonize the rhizosphere and, when applied to crops, exert a beneficial effect on plant growth, its yield and productivity. PGPR can act beneficially on plant growth directly (biofertilization, stimulation of root growth, rhizoremediation, and plant stress control) or indirectly (antibiosis, induction of systemic resistance, and competition for nutrients and niches). PGPR that have been successful in promoting the growth of crops such as strawberry, canola, soybean, lentil, pea, wheat and radish have been isolated. N₂-fixing and phosphate solubilizing bacteria, including Bacillus sp., Azotobacter sp., Azospirillum sp., Beijerinckia sp., Pseudomonas sp. are also widely used in organic plant growing. This review surveys the advances on biofertilizers based on plant-PGPB interaction research focusing on the principles and mechanisms of action of PGPB, both free-living and endophytic bacteria, and their use or potential use for the biological control of plant diseases.