MP Board · Class 12 · Biology · Microbes in Human WelfareExplain in detail the role of microbes as biofertilisers and biopesticides in sustainable agriculture. Discuss specific examples such as Rhizobium, Mycorrhiza, and Bacillus thuringiensis.

Introduction to Microbes in Agriculture\nMicrobes play an indispensable role in maintaining soil fertility and controlling plant pests without causing environmental degradation, making them crucial components of sustainable agriculture. Unlike synthetic chemical fertilizers and pesticides that lead to water pollution, soil toxicity, and resistance development in pests, microbial agents are eco-friendly, target-specific, and promote long-term ecological balance.

Microbes as Biofertilisers\nBiofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers include bacteria, fungi, and cyanobacteria.

• Nitrogen-Fixing Bacteria: Organisms like Rhizobium form symbiotic associations with the root nodules of legumes. They fix atmospheric nitrogen into organic compounds, which is readily usable by plants. Free-living bacteria like Azospirillum and Azotobacter also enrich the soil nitrogen content.
• Fungal Associations (Mycorrhiza): Many fungi form symbiotic associations with roots of higher plants, known as mycorrhiza. Glomus species are prominent examples. The fungal symbiont absorbs phosphorus from soil and passes it to the plant. Plants having mycorrhiza show resistance to root-borne pathogens, tolerance to salinity and drought, and overall an increase in plant growth and development.
• Cyanobacteria: These are autotrophic microbes widely distributed in aquatic and terrestrial environments, many of which can fix atmospheric nitrogen, e.g., Anabaena, Nostoc, Oscillatoria. In paddy fields, cyanobacteria serve as an important biofertiliser, increasing the organic matter of the soil.

Microbes as Biopesticides\nBiopesticides are certain types of biological pest control applied in a manner similar to chemical pesticides.

• Bacillus thuringiensis (Bt): Dried spore powders of Bacillus thuringiensis are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and kills the larvae. The bacterial disease gets into the caterpillars, effectively controlling pests without harming other insects.
• Nucleopolyhedrovirus (NPV): These are pathogens that attack insects and other arthropods. The majority of NPVs used as biological control agents are in the genus Baculovirus. They are excellent candidates for species-specific, narrow-spectrum insecticidal applications and have no negative impacts on plants, mammals, birds, fish, or even non-target insects.

Conclusion\nThus, integrating biofertilisers and biopesticides into farming practices reduces dependency on harmful chemicals, restores natural soil ecosystems, and ensures high agricultural yields sustainably for future generations.