Question

How do biofertilisers enrich the fertility of the soil?

Answer 1

Biofertilisers are micro-organisms that restore soil nutrients while maximising ecological advantages and minimising environmental dangers. 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 bacteria that forms an excellent symbiotic association with leguminous plants. It can fix 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 fix 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 fem. 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.