This article throws light upon the five main functions of micro-organisms present in soil.
1. Organic matter decomposition (By this process, plant and animal residues are broken down by micro-organisms into more simpler compounds, other slimy compounds, other slimy intermediate products organic acids and more resistant compound humus. All these products combinedly influence the physical and chemical properties of soil and hence the plant growth).
(a) De-nitrification process carried out by a particular micro-organisms and causes loss of gaseous nitrogen
(b) Development of various plant diseases
(c) Production of antibodies and other toxic substances.
(d) Competition for nutrients.
2. Inorganic transformations
(These processes are carried out by different groups of soil micro-organisms. Through this process organic form of different essential plant nutrients like N, P, S, Fe etc. are transformed into their respective inorganic forms and plants are able to absorb for their growth and development and so this process has of vital importance).
3. Fixation of Nitrogen
(i) Bacteriaâ€”Symbiotic nitrogen fixing bacteria e.g. Rhizobium
Non-symbiotic nitrogen fixing bacteria, e.g. Azotobacter, Azospirillum, Clostridium etc.
(ii) Cyanobacteria e.g. Nostoc, Aulosira, fertilisima Anabaena etc.
(iii) Actinomycetes e.g. Frankia
4. Formation and Development of soil
(i) Decomposition of rocks and minerals
(ii) Improvement of soil structure and stability of soil aggregates
(iii) Movement of soil materials etc.
5. Production of soil enzymes (stimulates the activity as well as increases the microbial population e.g. hydrolysis of urea by urease enzyme).