Manuers and Fertilizers


Bio-fertilizers are the preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulolyotic micro-organisms used for application to seed or composting areas with the objective of increasing the numbers of such micro-organisms and accelerating those microbial processes which augment the availability of nutrients that can be easily assimilated by plants. Bio-fertilizers harness atmospheric nitrogen with the help of specialized micro-organisms which may be free living in soil or symbiotic with plants. ‘Microbial inoculants’ are carrier based preparations containing beneficial micro-organisms in a viable state, intended for seed or soil application, designed to improve soil fertility and help plant growth by increasing the number of desired micro-organisms in plant rhizosphere.

Microbial Inoculants: - In soil the activities of Nitrogen fixation, mobilisation of plant nutrients and degradation of ligno-cellulotic wastes are being carried out by a large number of micro-organisms. Artificially multiplied cultures of selected micro organisms augment the natural recycling of organic resources. There are different types of microbial inoculants.

A.     Nitrogen fixers

  1. Symbiotic: - Rhizobium, inoculants for


  1. Non-symbiotic: - For cereals, millets, and vegetables.

a) Bacteria:-

i). Aerobic:-Azatobacter, Azomonas, Azospirillum.

ii) Anaerobic:- Closteridium, chlorobium

iii) Facultative anaerobes- Bacillus, Eisherichia

b) Blue green algae- Anabaena, Anabaenopsis, Nostoe

A.     Phosphate solubilizing micro-organisms.

B.     Cellulolytic and lignolytic micro-organisms.

C.     Sulphur dissolving bacteria.

D.     Azolla.

1.Rhizobium Inoculant

Inoculation: - Carrier based inoculants are mixed with little water to form slurry (sugar or gum added to enhance survival of Rhizobia) and seeds are uniformly coated with the inoculant, dried and sown immediately. Other specialized methods include-pelleted seed (for acidic soils), per-inoculated seeds, liquid and frozen concentrates, granular soil inoculants, porous gypsum granules and natural peat granule.

Agronomic importance: - Response to Rhizobium inoculation has been amply demonstrated with most of the legumes-ahar, urd, mung, gram, soybean, etc. Besides, legume cultivation also leaves behind a naturally nitrogen enriched soil for subsequent cultivators...

2.Azotobacter Inoculants

Inoculation: - A slurry of the carrier based inoculant is made with minimum amount of water and seeds are mixed with the slurry, dried in shade and sown; seedling dip (10-13 min) in slurry is done for transplanted crops and planted immediately. For sugarcane etc. secondary inoculation with slurry near the root zone in early stages of plant growth are also recommended. The inoculants can also be mixed with FYM and broadcast near the root zone.

Crop response: - Azotobacter inoculants on onion, wheat, rice, brinjal, tomato, cabbage, sugarcane, oat, barely, maize, potato can increase 7-12 % crop yields. Azotobacter spp. Increase plant yield primarily by fixing molecular nitrogen in soil, but it is also reported to synthesize auxins, vitamins, growth substances and antifungal antibiotics, which have beneficial effects of this bacterium on seed germination etc.

3.Azospirillum Inoculants

Occurrence in soil:- Soil pH in range of 5.6- 7.2 registers Azospirillum activity with optimum at 6.7 to 7.0; below pH 5.6 the soil is devoid of Azospillium and presence of organic matter in soil generally favours multiplication of this bacterium.Powdered and sterilized FYM+soil, FYM alone or FYM+charcoal are used as carriers.

4.Blue Green Algal Inoculants:

The inoculants are specially recommended for paddy crop grown in wet land conditions which also favour the growth of bluegreen algae. These algae also possess photosynthetic activity. Besides they excrete vitamin B12, auxins and ascorbic acid which contribute to growth of rice plants.

5.Azolla- an Organic Manure

Methods of application: - It is applied as green manure prior to rice planting and as dual cropping with rice, when fern grows side by side with paddy.

Crop response: - Soil application is more beneficial than dual culture method; 10 tonnes fresh Azolla/ha is equivalent to 25-30 kg N/ha and increasing application rate from 5-20 tonnes/ha has direct response in grain yield of paddy.