How are microbial innoculants used to increase the soil fertility?

Explanation

(i) Biofertilizers are defined as preparations containing living cells or latent cells of efficient strains of microorganisms that help crop plants uptake of nutrients by their interactions in the rhizosphere when applied through seed or soil.
(ii) Biofertilizers are also called as microbial cultures, bioinoculants, bacterial inoculants or bacterial fertilizers.
Advantages:
(i) They are efficient in fixing nitrogen, solubilising phosphate and decomposing cellulose.
(ii) They are designed to improve the soil fertility, plant growth, and also the number and biological activity of beneficial microorganisms in the soil.
(iii) They are ecofriendly organic agro inputs and are more efficient and cost effective than chemical fertilizers.
Examples:
Rhizobium:
(i) Bio-fertilisers containing rhizobium bacteria are called rhizobium bio-fertilizer culture.
(ii) They are symbiotic bacteria living inside the root nodules and convert the atmospheric nitrogen into a bio available form to the plants.
(iii) This nitrogen fixing bacterium when applied to the soil undergoes multiplication and fixes the atmospheric nitrogen in the soil.
(iv) Rhizobium is best suited for the paddy fields which increase the yield by 15 - 40%.
Azolla:
Azolla is a free-floating water fern that fixes the atmospheric nitrogen in association with nitrogen fixing blue green alga Anabaena azolla. It is used as a bio-fertilizer for wetland rice cultivation and is known to contribute 40-60 kg/ha/ crop.
Arbuscular mycorrhizae:
(i) Arbuscular mycorrhizae (AM) is formed by the symbiotic association between certain phycomycetous fungi and angiosperm roots.
(ii) They have the ability to dissolve the phosphates found in abundance in the soil and provides necessary strength to resist disease, germs and unfavourable weather conditions. It also assures water availability.