Agriculture and Farming Technology Updates

Blue-Green Algae: A great option for organic fertilizer growers to increase yield and earnings

Blue green algae is such an organic fertilizer that keeps the soil fertile for years


Blue-Green Algae (Cyanobacteria) are a special type of moss or aquatic vegetation. This is a great organic fertilizer. Farmers can grow it easily and adopt it as an additional source of income. Blue-green algae are free-living bacteria that absorb atmospheric nitrogen while photosynthesizing like plants. That is why blue green algae are grown regularly and it is used as organic manure. It is also used to treat acidic and alkaline soils.

Blue green algae are a special group of aquatic plants. It is also called ‘cyanobacteria’. It is a single-celled bacterium and is shaped like algae. That is why it is also called blue-green algae. By spraying it, the most important nutrient i.e. nitrogen in the soil of the fields is replenished. The nitrogen cycle is strengthened by blue-green algae. This leads to the stabilization of nitrogen in the soil.

Benefits of using blue-green algae

Blue-green algae are mainly put in the paddy fields, because the paddy field is always full of water. Due to this, blue-green algae get a favorable environment for continuous growth and development in the paddy fields. By its use, about 20 to 40 kg per hectare of nitrogen is fixed to the paddy crop. The use of blue-green algae increases the amount of organic matter and other nutrients in the soil like oxin, gibberellin, phyridoxine, indole acetic acid etc.

The use of blue green algae not only increases the yield of paddy, but also benefits from increased nitrogen and other nutrients in the soil for post-paddy rabi crops. All these nutrients help in seed germination and cropping and growth is also better. In this way, the use of blue green algae gives immediate as well as far-reaching benefits. If this organic manure is used continuously for 3 to 4 years in the field, then there is no need to treat the soil with algae for the next several years, because the fertility of the soil remains intact.  

Treatment of blue-green algae in paddy field 

According to the experts of Microbial Research and Production Center of Jawaharlal Nehru Agricultural University, Jabalpur, the soil should be treated by sprinkling 10 kg dry powder of blue green algae in the entire field in 6 to 10 days from the planting of plants in the paddy field. Not only should the field be filled with 8 to 10 cm of water before treatment, but after spraying this organic manure, the field should also be filled with water for at least the next 20 days. Due to this, the growth and dispersal of blue green algae is done very well. This growth and spread of algae helps to fix atmospheric nitrogen.

In the field treated with blue green algae, any crop can be grown in the next season. Experts have found that gram cultivation after paddy on treated land proves to be very beneficial. That is why this organic manure is a cheap and easy alternative to nitrogenous chemical fertilizers. The names of the species of blue green algae are – Nostak, Anabaena, Calothrix, Cytoma, Tolipothrix etc.  

How to Produce Blue Green Algae? 

  • In any open place away from the shadow, where the water source is near, prepare a pit 5 to 10 meters long and 1 to 1.5 meters wide and about 15 cm deep as per your requirement. Keep the soil removed from the pit on a pail around the pit, so that the depth of the pit increases further. Be sure to leave a space of about two feet between two such pits for monitoring and movement. 
  • Keep filling this pit with water continuously for 2-3 days. Due to this there will be a time when the speed of seepage of water from the pit will be very slow. 
  • After this, sprinkle super phosphate or rock phosphate at the rate of 100 grams per square meter according to the volume of the pit in the very wet soil of the pit and mix it well with the soil by hand. If the field is of black soil, then lime should also be added at the rate of about 25 grams per square meter. 
  • Then fill the above pits with water up to 15 cm and sprinkle 250 grams mother culture of blue green algae in it. To get the mother culture, one should contact any other blue green algae grower or your nearest Krishi Vigyan Kendra or agriculture officials. 
  • Along with sprinkling the mother culture of blue green algae in the pit, apply one ml of Malathion or Carbofuran @ 3 grams per square meter to kill the seasonal insects. 
  • Now the mother culture of blue green algae will continue to grow. Just keep in mind that the pit never dries up. If there is a shortage of water in the pit, then fill it with enough water in the morning or evening so that its water level must be maintained up to 10-15 cm. 
  • If the pits are carefully observed after 3-4 days, the colour of the surface of water will start to change. This change of colour is a symbol of growth of blue green algae. In the next 10-15 days a thick layer of blue green algae will be seen floating on the water. 
  • Collect this floating blue green algae culture in a vessel. This product will not contain any traces of clay. Therefore, it can be used again as a mother culture for another pit. 
  • The blue green algae culture produced in the pits is extracted in two ways. First, the pit should be allowed to dry completely for two days and then from there the dried crust of blue green algae is collected and kept in clean bags. Another method is to remove the thick layer of blue green algae in a wet state with a sieve, dry it completely and then collect it in bags. 
  • This dried blue green algae culture is the organic fertilizer for which all the above exercise was done to find it. In this way the dried manure can be sprayed in the field. 
  • Blue green algae culture grows well in neutral or slightly alkaline soils. 

Precautions for the use of blue green algae

  • The field in which this organic manure is to be applied should be filled with water and special care should be taken that the field does not dry up after spraying blue green algae.
  • Apply full amount of phosphorus while preparing the field for transplanting paddy because the presence of phosphorus in the soil is very important for the growth of blue green algae.
  • Use necessary insecticides in case of aquatic pests in the field. Pesticides do not adversely affect the growth of blue green algae.
  • If green fibrous local algae are seen during the cultivation of blue green algae, then a 0.05 percent solution of Nila Thoth (Copper Sulphate) (one gram in one litre of water) should be sprayed in the cisterns. This spraying may also need to be done from time to time.
  • After taking production from any pit thrice, re-apply half of the rock phosphate i.e. 100 grams of rock phosphate per square meter.
  • Be sure to spray insecticides if pests are seen in any pit. Otherwise the production of blue green algae is adversely affected.
  • As soon as green algae appear in the pits, dissolve 1 gram of Neelathotha in 1 litre of water and spray it. This kills the green algae in 3-4 days.
  • A minimum temperature of 30-45°C is required for the production of blue green algae. Sunshine should also fall on the pits. 

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