Hi
Azolla a dichotomously branched free floating aquatic fern is naturally available mostly on moist soils, ditches marshy ponds and is widely distributed in tropical belt of India. The shape of Indian species is typically triangular measuring about 1.5 to 3.0 cm in length 1 to 2 cm in breadth. Roots emanating from growing branches remained suspended in water. The dorsal lobe which remains exposed to air is having a specific cavity containing its symbiotic partner, a Blue Green Algae (BGA), the Anabaena Azolae. The fern is capable of fixing atmospheric nitrogen in the soil I the form of NH4+ and becomes available as a soluble nitrogen for the wet land rice crop, which is the major cereal for the people of the North East. Owing to the poor economic conditions of the farmers of the North Eastern States, rice crop is mostly grown under natural soil fertility with minimum inputs and amelioratives. But for taking a good crop of rice, judicious application of nutrients is necessary. Besides, this, the farmers of the state of Meghalaya and other north eastern states have apathy in using chemical fertilizers in crop production. For sustainable crop production, there is a practice to supply some quantity of nutrients through organic manure, viz; FYM and composted plant residues and bio-fertilizers.
Adaptability
Azolla Caroliniana, Wield is identified as a cold tolerant species and survives well even at very low winter temperature of 5ºC during the months of December to February in mid hills of Meghalaya. Azolla pinnata, L is a local isolate found widely in the entire North Eastern Region, but does not survive under mid hills of Meghalaya. However, Azolla caroliniana, Wield has shown its adaptability in hills and other similar locations.
Azolla caroliniana, Wield can be preserved in shallow pound having -15 cm of standing water and by providing shade 1-0-15 cm above the pond water surface through weeds or paddy straw. For raising Azolla inoculum a pond size of 3 M x 2 M x 1 M is most desirable. Under such weed or straw mulch cover, the Azolla multiplies rapidly and inoculum will be ready within a period of 20-25 days for further releasing in the main multiplication ponds on the onset of monsoon in the month of April.
How to grow Azolla?
*
In low land, field is ploughed; leveled and small bunds of 50 cm width are made to make small ponds of 3 x 2 x 1 M size.
*
Only 10-15 cm standing water is allowed in the ponds.
*
The green Azolla @ 50 -200 g/sqm + PO through SSP @ 20 kg/ha along with Furadan 1 g/kg of Azolla is mixed and released in the pond maintaining a 10-15 cm of water level, for further growth and multiplication of Azolla.
*
Azolla multiplies rapidly and form a green mat like a carpet on water surface of ponds in just two weeks. This green Azolla is harvested in bamboo basket and transferred and released in the transplanted rice field for further multiplication, as dual cropping with rice for fixing nitrogen to rice crop.
*
Harvested green Azolla could be converted in to compost by pounding in pits for a month which is then used like FYM for other crops grown under upland situation.
Favourable condition for higher efficacy of Azolla
*
Water: 10-15 cm fresh current water is necessary in multiplication pond.
*
Temperature: the day/night temperatures ranging between 32ºC and 20ºC have found to be most favourable. The optimum temperature for luxurious growth of Azolla is 25-30ºC and can be raised successfully in the mid hills.
*
Light: Azolla prefers to grow well under partial shade. As dual cropping Azolla gets partial shade from rice plant and therefore as dual cropping with rice is most successful.
*
Soil pH: Azolla grows well in slightly acidic soil having 5.2 to 5.8 pH.
Nutrition
Being an N fixing fern Azolla does not require nitrogenous fertilizer for its growth. However application of N @ kg/ha is useful as a starting dose in new multiplication area. Phosphorous @ kg/ha is desirable for good bio-mass production.
Yield
Azolla produces around 300 tonnes of green bio-hectare per year under normal sub tropical climate which is comparable to 800 kg of N (1800 kg of urea).
Regards
asshwini
