Question

How do biofertilisers enrich the fertility of the soil?

Answer 1

Biofertilisers are microorganisms that restore soil nutrient levels while maximising ecological benefits and minimising environmental risks. Biofertilizers are mostly derived from bacteria, fungi, and cyanobacteria. Here are some of the biofertilizers and their role in sustaining soil fertility:

1. Free-living nitrogen-fixing bacteria fix atmospheric nitrogen in the soil, making it available to higher plants. The best example is Azotobacter. Apart from Clostridium, Bacillus polymyxa, and Derxia are also known to fix atmospheric nitrogen.
2. Rhizobium is a nitrogen-fixing bacterium that forms an excellent symbiotic association with leguminous plants. It can convert up to 500 kg of nitrogen per hectare of soil and produces nodules on the roots of leguminous plants.
3. Anabaena, Nostoc, Aulosira, Stigonema, and other cyanobacteria that assimilate nitrogen are free-living. Aulosira fertilissimma is thought to be the most active nitrogen fixer in rice fields in India.
4. Nitrogen-fixing cyanobacteria have symbiotic relationships with various plants, including cycad roots, lichens, liverworts, and Azolla (female). Among these, the Azolla-Anabaena connection is very important to agriculture. Anabaena azollae lives in the leaf cavities of ferns. It fixes nitrogen.
5. Fungi can also create symbiotic relationships with plants (mycorrhiza). The fungal symbiont in these partnerships obtains phosphorus from the soil and transfers it to the plant. Plants with such relationships exhibit additional benefits, including resistance to root-borne pathogens, tolerance to salinity and drought, and an overall improvement in plant growth and development.

Answer 2

Biofertilisers enrich the fertility of the soil by using living microorganisms such as bacteria, fungi, and cyanobacteria that increase the nutrient quality of the soil. These microbes convert atmospheric nitrogen into organic forms that plants can absorb as nutrients. For example, Rhizobium bacteria live symbiotically in nodules on legume roots and convert nitrogen, while bacteria like Azospirillum and Azotobacter fix nitrogen freely in the soil. Cyanobacteria in paddy fields add organic matter, further enriching the soil. Thus, biofertilisers enhance soil fertility naturally by increasing nutrient availability, especially nitrogen, thereby supporting plant growth and improving crop yields.