Question

Name the different types of microorganisms used as bio-fertilizers in organic farming and explain how each contributes to soil fertility.

Hint:

Glomus = Phosphorus. Rhizobium = Nitrogen. Always link the specific microbe to the specific nutrient it provides.

Answer 1

Step 1: Understanding the Concept:
Different microbes have specialized roles in nutrient cycling within the soil.
Step 2: Detailed Explanation:
1. Bacteria: \textit{Rhizobium} forms symbiotic associations with legume roots to fix atmospheric nitrogen. Free-living bacteria like \textit{Azotobacter} and \textit{Azospirillum} also fix nitrogen directly into the soil.
2. Fungi: Fungi form symbiotic associations with plants called Mycorrhiza (e.g., genus \textit{Glomus}). The fungus absorbs phosphorus from the soil and passes it to the plant. It also provides resistance to root-borne pathogens and salinity.
3. Cyanobacteria: Blue-green algae like \textit{Anabaena}, \textit{Nostoc}, and \textit{Oscillatoria} can fix atmospheric nitrogen. In paddy fields, they serve as an important bio-fertilizer and also add organic matter to the soil.
Step 3: Final Answer:
Microbes include bacteria (fix nitrogen), fungi (absorb phosphorus), and cyanobacteria (fix nitrogen and add organic matter).