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Bio-inoculants are living organisms containing strains of specific bacteria, fungi, or algae which:

- take nitrogen from the air and make it available to plants- reducing the need for nitrogen fertilizer.

- make inorganic phosphate and micronutrients soluble and available to plants.

- collect and store available nutrients.

- enhance plant uptake of phosphorus and zinc.

- provide physical barriers against pathogens.

- stimulate plant growth.

- decompose organic residues.

Biological nitrogen-fixation

Atmospheric nitrogen is taken from the air-or "fixed"-by micro-organisms which live on some leguminous and non leguminous plants.


These bacteria live in nodules on the roots of legumes. Legume seeds can be inoculated to encourage the growth of nitrogen fixing nodules.


- meet 80 to 90 percent of the nitrogen requirements of legume crops.
- increase production of legume crone.
- benefit successive crops.
- minimize the chance of crop failure.
- increase soil fertility.
- are cost effective.
- are pollution free.

Nodules on a legume plant

About 200 g of good quality rhizobium culture is enough to

An, treat 12-15 kg of seed. There are specific cultures for different crops. You can buy rhizobium inoculant from agricultural extension centres, agricultural universities, private dealers, and the National Biofertilizer Development Centre, Ghaziabad, Uttar Pradesh.

Azotobacter and Azospirillum

These bacteria fix atmospheric nitrogen in cereal crops. Azotobacter produce antifungal compounds against many plant pathogens and control nematode diseases. Azospirillum increase germination and improve vigour of young plants. One kg of seed needs 5 g of inoculant. This will fix 30 kg/ha of nitrogen per year.

Blue-green algae

Blue-green algae can fix 25-30 kg/ha of nitrogen per year. A paddy crop needs 10 kg/ha of algal powder, available from the National Biofertilizer Development Centre. Algal powder is not required after 3-4 years of continuous use in the field.

Blue-green algae in a paddy crop:

- produces 25-30 kg nitrogen (equivalent to 55-65 kg urea) per ha, and enhances yield 10 to 12 percent.

- is cost effective and pollution free.

- provides more oxygen to paddy roots.

- benefits the next crop.

Algae production

1 Prepare shallow trays (2 m x 1 m x 20 cm) of galvanized iron sheet. The size can be increased if more material is to be produced.

2 Spread 8-10 kg of soil and mix well with 200 g of super phosphate.

3 Add water to the trays (5 to 15 cm deep) depending on the rate of evaporation. The soil should be about neutral. If it is acidic, add lime.

4 After the soil has settled, sprinkle the algal culture on the surface of the standing water. Keep the trays in the open air, in direct sunlight.

5 Growth of the algae will be rapid in the hot summer months and in about 7 to 10 days they will form a thick mat. If the daily rate of evaporation is high, add water regularly. When the algal growth becomes sufficiently thick, stop watering.


Azolla is a floating fresh water fern. It grows in stagnant water. The fern forms a green mat over the water surface. It readily decomposes to ammonia which is available to rice plants. Apply 10 kg of powdered, dry azolla fern per hectare.

Application Seed treatment-Rhizoblum and Azotobacter Top dressing-Rhizoblum, Azotobacter, PSM Crops Legumes-Rhizablum + PSM Cereal-Azotobacter + PSM Legumes mixed with nonlegumes-Rhizoblum + Azotobacter + PSM

For more information contact the National Biofertilizer Development Centre, CGO Complex 11, Ghaziabad Uttar Pradesh 201002, India.


Mycorrhiza are fungi which live in association with the roots of crops. The fungi stimulate plant growth, help the plants use phosphate, and protect the plants from disease. One kg of crop seed needs 7-10 g of inoculant, available from Mycology and Plant Pathology Division, Indian Agricultural Research Institute, and the Department of Botany, Delhi University.


Phosphate solubilising micro-organisms (PSM) convert soil phosphorus into forms that plants can use. To use PSM, mix 3 kg of PSM, 50 kg of farmyard manure, and the crop seed. Drill them together.

Methods of application

Bio-inoculants can be used two ways: as seed treatment and as top dressing in the soil.

Seed treatment

Moisten the seed and sprinkle the inoculum at a rate of 5-10 g per kg of moist seed. Mix thoroughly and dry in the shade for an hour. Sow the inoculated seed immediately.

Top dressing

For legumes, mix 1.5 kg rhizobium or 0.5 kg Azotobacter or 3 kg PSM in 50 kg of farmyard manure or compost. Top dress.

For cereals and millets, use 2 kg of PSM.


Mix 3 kg of PSM with 100 kg of farmyard manure and broadcast the granular mixture. Can be broadcast in a standing crop seed treatment

Source: Dr. W. R. Deshpande