Azolla is an aquatic fern consisting of a short, branched, floating stem with roots that hang down in the water. The leaves are alternately arranged, each consisting of thick aerial dorsal lobe containing green chlorophyll and a slightly larger thin, colourless, floating ventral lobe. The plant diameter ranges from 1-2.5 cm for small species like Azolla pinnata, to 15 cm or more like Azolla nilotica. They are triangular or polygonal in shape, and float on the surface of the water, individually or in mats. They give the appearance of a dark green to reddish carpet (rarely produced anthocyanin pigments), except Azolla nilotica which do not produce the red anthocyanin pigment.
The most interesting characteristic of azolla is its symbiotic relationship with the nitrogen-fixing blue-green alga (cyanobacterium) Anabaena azollae. The fern provides nutrients and a protective cavity in each leaf to Anabaena colonies in exchange for fixed atmospheric nitrogen and possibly other growth-promoting substances.
Azolla is new to India. However, it has been recognized as a useful plant in Southern China and Northern Vietnam, where it was used as a biofertilizer and green manure for the rice crop. Azolla production promoted heavily during 1960s in China and Vietnam not only resulted in rapid expansion in these countries, but also attracted world attention in the 1970s. While it was at peak during 1980s along with Blue green Algae, both slowly reduced in use. It was also considered as a noxious weed by farmers
Fairy moss, Duckweed fern, Mosquito fern, Water fern [English]; helecho mosquito, helecho de agua [Spanish]; Algenfarne [German]; अजोला [Hindi]; അസോള [Malayalam]; அசோலா [Tamil];
Azolla Species [Azollaceae]
Azolla is very rich in proteins, essential amino acids, vitamins (vitamin A, vitamin B12, Beta Carotene), growth p
romoter intermediaries and minerals including calcium, phosphorous, potassium, ferrous, copper, magnesium. On dry weight basis, Azolla has 25-35% protein content, 15% crude fibre, 10-15% mineral content (iron – (1000–8600 ppm dry weight, copper – 3–210 ppm dry weight, manganese -120–2700 ppm dry weight), and 7-10% comprising a combination of amino acids, bio-active substances and biopolymers (vitamin A – 300–600 ppm dry weight), 15% ash, 30% nitrogen. Azolla’s carbohydrate and oil contents are very low (4.8–6.7% dry weight crude fat, with 6.1–7.7% and 12.8– 26.4% total fat for the poly
unsaturated acids omega 3 and omega 6.
In addition, Azolla do not to accumulate secondary plant compounds and therefore has a greater potential than tree leaves to source protein for monogastric animals. One hectare of Azolla can produce 540-720 kg of protein per month.
Normally azolla is grown in paddy fields or shallow water bodies and multiplies very rapidly over a period of time if the climate is conducive for its growth.
Bed Preparation and Maintenance
Azolla as cattle feed
Comparison of biomass and protein cotent of azolla with different fodder species (t/ha)
Annual production of biomass
Dry matter content
P. Kamalasanana Pillai, S. Premalatha and S. Rajamony. LEISA