Question

What is the role of micro-organism in increasing the fertility of the soil?

Answer 1

The use of the chemical fertilizers to meet the ever-increasing demand of agricultural produce has contributed significantly to environmental pollution. So, microorganisms help in increasing the fertility of the soil. The microorganisms which are used for increasing fertility of the soil are known as biofertilisers and this type of farming is known as organic farming. Biofertilisers provide optimum nutrients to crop plants. They enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.

1. Bacteria: Rhizobium forms the symbiotic association with root nodules of leguminous plants. These bacteria fix atmospheric nitrogen into organic forms, which is used by plants as nutrients. Bacteria like Azospirillium and Azotobacter can fix atmospheric nitrogen while free-living in the soil, thus enriching the nitrogen content of the soil.
2. Fungi: Fungi also forms symbiotic associations with roots of higher plants, known as Mycorrhiza. The fungal symbiont absorbs phosphorus from soil and passes it to plants. In return, fungi get shelter and food from this association.
3. Cyanobacteria: Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen e.g., Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue-green algae also add organic matter to the soil and increase its fertility.