Explain in detail the role of microbes as biofertilisers. Give suitable examples of free-living and symbiotic nitrogen-fixing organisms and describe how they enrich the nutrient quality of the soil.

Q: Explain in detail the role of microbes as biofertilisers. Give suitable examples of free-living and symbiotic nitrogen-fixing organisms and describe how they enrich the nutrient quality of the soil.

Introduction to Biofertilisers\nBiofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi, and cyanobacteria. Unlike chemical fertilisers which cause pollution and environmental degradation, biofertilisers are eco-friendly and sustainable alternatives in modern agriculture. Role of Rhizobium (Symbiotic Nitrogen Fixation)\nRhizobium is a classic example of a symbiotic bacterium that forms root nodules in leguminous plants (such as beans, peas, and pulses). These bacteria fix atmospheric nitrogen into organic compounds, which is readily used by the host plants as a nutrient. In return, the plant provides shelter and food to the bacteria. Free-Living Nitrogen-Fixing Bacteria\nOrganisms such as Azotobacter and Azospirillum are free-living bacteria residing in the soil. They take up free nitrogen gas from the atmosphere and convert it into nitrogenous compounds, thereby enriching the soil nitrogen content independently without needing a specific host plant. Mycorrhiza (Fungal Association)\nMycorrhiza represents a symbiotic association between fungi and the roots of higher plants. Fungi such as Glomus species form this association. The fungal symbiont absorbs phosphorus from the soil and passes it to the plant. Plants with mycorrhizae show resistance to root-borne pathogens, tolerance to salinity and drought, and overall an overall increase in plant growth and development. Cyanobacteria as Biofertilisers\nCyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments, such as Anabaena, Nostoc, and Oscillatoria. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue-green algae also add organic matter to the soil and increase its overall fertility and moisture-retention capacity.

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Introduction to Biofertilisers
Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi, and cyanobacteria. Unlike chemical fertilisers which cause pollution and environmental degradation, biofertilisers are eco-friendly and sustainable alternatives in modern agriculture. Role of Rhizobium (Symbiotic Nitrogen Fixation)
Rhizobium is a classic example of a symbiotic bacterium that forms root nodules in leguminous plants (such as beans, peas, and pulses). These bacteria fix atmospheric nitrogen into organic compounds, which is readily used by the host plants as a nutrient. In return, the plant provides shelter and food to the bacteria. Free-Living Nitrogen-Fixing Bacteria
Organisms such as Azotobacter and Azospirillum are free-living bacteria residing in the soil. They take up free nitrogen gas from the atmosphere and convert it into nitrogenous compounds, thereby enriching the soil nitrogen content independently without needing a specific host plant. Mycorrhiza (Fungal Association)
Mycorrhiza represents a symbiotic association between fungi and the roots of higher plants. Fungi such as Glomus species form this association. The fungal symbiont absorbs phosphorus from the soil and passes it to the plant. Plants with mycorrhizae show resistance to root-borne pathogens, tolerance to salinity and drought, and overall an overall increase in plant growth and development. Cyanobacteria as Biofertilisers
Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments, such as Anabaena, Nostoc, and Oscillatoria. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue-green algae also add organic matter to the soil and increase its overall fertility and moisture-retention capacity.

MP Board · Class 12 · Biology · Microbes in Human WelfareExplain in detail the role of microbes as biofertilisers. Give suitable examples of free-living and symbiotic nitrogen-fixing organisms and describe how they enrich the nutrient quality of the soil.