Azolla and its multiple uses in agriculture

Dr. Sanjay Kumar Ray
ACTO (Soil Science), KVK,
ICAR Research Complex for NEH Region, Nagaland Centre-797106


1. Introduction:

Azolla an aquatic floating fern is an excellent biofertilizer used as green manure in rice cultivation; feed for livestock and employed as bioremediation of polluted soil and water bodies. It grows naturally in the stagnant water of drain, canal, pond, rivers, harbor, and marshy lands. The ability of this fern is to fix atmospheric nitrogen (N) at a faster rate due to the presence of heterocystous cyanobacterium Anabaena-Azollae, which is confined to the dorsal leaf hole of this fern. Azolla is also a very rich source of proteins, essential amino acids, vitamins (vitamin A, vitamin B12 and Beta carotene), growth promoter intermediaries and minerals like calcium (Ca), phosphorus (P), potassium (K), iron (Fe), copper (Cu), magnesium (Mg) etc. Because of high nutritional quality it becomes as an ideal feed for livestock.


2. Advantage of Azolla:


Azolla can grow easily in both the wild and under controlled conditions, doubles its biomass within 3 to 5 days that produced huge quantities of biomass throughout the seasons.

  • Azolla suppresses tender weed growth and minimize evaporation losses of soil water in the rice field and it cannot compete with rice for light and space.
  •  Azolla is rich source of nutrient and it’s the most economic and efficient feed substitutes for livestock.
  •  Azolla contains most of the nutrients which are required for all classes of livestock including poultry and fish.


Fig. 1, 2 and 3. Steps of homestead level azolla multiplication.

4. Growth and Multiplication Techniques of Azolla:


4.1. Environment Required for Azolla Multiplication: Water is the fundamental requirement for the growth and multiplication of Azolla. It is extremely sensitive to lack of water. The optimum pH ranges varied from 4.5 to 7.0. Generally, azolla requires 25 to 50% of full sunlight for its normal growth; slight shade is of benefit to its growth. Azolla needs all the macro and micro nutrients for its normal growth and vegetative multiplication, but phosphorus is often the most limiting element for its growth. The optimum temperature for growth of all the azolla species is around 25ºC. The optimum relative humidity for azolla growth is between 85 to 90 percent. Azolla becomes dry and fragile at a relative humidity lower than 60 percent.


4.2. Multiplication Techniques: Azolla can be multiplied in nursery plots, ponds, ditches, canals, concrete tanks and polythene lined ditches. Homestead and field level multiplication methods are commonly used.


4.2.1. Homestead Method:
Materials Requirements: Silpauline sheet (3×2 Sqm) of 150-300 GSM, sieved fertile soil, organic manure (FYM, vermicompost, pig manure, etc.), rock phosphate (RP)/single super phosphate (SSP), micronutrients, culture of azolla (mother inoculum) and neem oil.


Selected area should be partially shed > Prepared multiplication pit with the size of 2 m length, 1m width and 0.2 m depth >Spread silpauline sheet over the pit >Mud plastering the surroundings and then pour water upto10-15 cm level (Fig 1, 2 and 3) >Add 20-25 kg top fertile soil, 10-15 kg organic manure, 100gm SSP/RP, 50gm MOP and micronutrients 20 g >Spread fresh azolla culture 500 g >Multiply for 15 days, then harvest >Spray neem oil @ 4ml/litre to avoid pest and disease incidence.


5. Use of Azolla in Rice: Azolla biofertilizer may be applied in two methods for wetland rice. In the first method, fresh azolla biomass are inoculated (multiplied) in rice field before transplanting and incorporated as green manure form. This method requires huge quantities of fresh azolla culture. In the other method, azolla may be inoculated after transplanting rice and grown as a dual crop or intercrop with rice @ 300 g/sqm. The azolla biomass are formed within 3 weeks and then water from rice field is drained out for azolla decay into the soil.


6. Use of Azolla as Livestock Feed: Azolla can be used as an ideal source of feed for cattle, sheep, goats, pigs, rabbit, poultry and fish. About 20-25% of the commercial feed can be replaced by the using of fresh azolla biomass. Azolla in dried form is not preferred by the livestock for that reason fresh azolla is always should use. Before feeding the fresh azolla to livestock, it should be washed thoroughly to get rid of cow dung smell. The cleaned azolla can also be mixed with commercial feed and mixture or can be directly fed to livestock.


7. Conclusion: In view of the declining soil health and productivity due to the increase anthropogenic activities. The Azolla-Anabaena is an excellent low-cost biofertilizer for rice as good as an ideal feeding substitute for livestock, so the attention is required to address certain key issue in azolla for its exploitation and better employment in agriculture and allied sectors. It already becomes popular and cultivated widely in other countries like China, Vietnam and Philippines etc. and is yet to be taken up in India in a big way. Therefore, a large number of hands on training cum demonstration will be needed to conduct on reproduction, maintenance, easy multiplication, utilizations systems of azolla and its efficient stain should be made available at the doorstep to the farmers.