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Anabaena azollae : A potential algal biofertilizer for rice crop

Ashmrita Mahto & Radha Sahu*
Algal Biotechnology Laboratory, Department of Botany, R.U., Ranchi, Jharkhand
Received 13th December, 2009; Revised 15th February, 2010

Abstract : Anabaena azollae a filamentous nitrogen fixing cyanobacterium is found in symbiotic association with a heterosporous water fern Azolla. It multiplies repidly by vegetatively means and its growth is prolific. Its application increase the yield of rice by 12.7%. It application as a green manure has been used in China and other Asian countries . A field study was conducted at Kokar Ranchi with rice IR 64. For this purpose two field plots of 10 m2 area were prepared one without Azolla which acted as control and other with Azolla. The soil was found to be acidic after testing in B.A.U Ranchi rice seediling were transplanted  in the flooded field. Ten days after transplantation Fresh Azolla were inoculated in the ratio of 0.4 – 0.5 kg/m2. The symbiotic association of  A. azollae fixes the atmospheric nitrogen gas (N2) and combine with H2 to from (NH3). This vital process along with nitrification (formation of nitrites & nitrate) and ammonification (formation of ammonia from protein decay ) make nitrogen available to rice plants. N2 gas (Atmospheric nitrogen) :  N= N+ 12ATP  Nitrogenase   NH3 + 12 ADP + Pi The effect of Anabaena azollae biofertilizer on rice plants was seen by its rapid growth It has bright green and thick, fleshy stem having large number of leaves. The tilleres were seen after 80 days and showed large thick and health food grains as compared with the control. The grain yield was found to be increased in the tune of 10-13% over control. This observation clearly indicates that the application of Azolla as manure can replace the chemical fertilizers.


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