Immobilized cyanobacteria as a biofertilizer for rice crops; Intl. Conference on Applied Algology, Knysna, South Africa, April 1996. |
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Authors: | S Kannaiyan S J Aruna S Merina Prem Kumari D O Hall |
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Institution: | (1) Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, 641 003 Tamil Nadu, India;(2) Division of Life Sciences, King's College London, London, W8 7AH, UK |
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Abstract: | N2-fixing cyanobacteria (Anabaena azollae, symbiont strains) were immobilized in polyurethane foam and ammonia production by
the cyanobacteria was investigated in the laboratory and rice field. The cyanobacterial symbiont, A. azollae - MPK-SK-AM-24
showed the highest growth rate and biomass production amongst the 5 isolates examined while A. azollae-AS-DS showed the highest
nitrogenase activity followed by A. variabilis - SA0 (wild type, non-symbiotic). Treatment of the foam-immobilized cyanobacteria with the systemic fungicide Bavistin stimulated
nitrogenase activity while inhibiting glutamine synthetase (GS) activity. Free-living A. azollae-MPK-SK-AF-38, A. azollae
- MPK-SK-AM-24 and A. azollae-MPK-SK-AM-27 excreted the highest amounts of ammonia into the growth medium; under foam - immobilized
conditions the ammonia production increased further. Treatment of the foam - immobilized cyanobacteria with the fungicides
Bavistin and Vitavax resulted in ammonia production at significantly higher rates. Rice seedlings (var. ADT 36) grown in the
laboratory in conjunction with foam - immobilized A. azollae showed increased growth. A field experiment with paddy rice and
foam - immobilized A. azollae strains indicated that the cyanobacteria excreted significant amounts of ammonia into the flood
water in the rice fields resulting in increased chlorophyll content of the plants and increased the rice grain and straw yields.
A combination of fertilizer nitrogen and inoculation with foam - immobilized cyanobacteria also significantly increased the
rice grain and straw yield. Additionally, both A. azollae and A. variabilis were immobilized in sugarcane waste (bagasse),
added to rice paddy and resulted in increased rice grain yield.
This revised version was published online in September 2006 with corrections to the Cover Date. |
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Keywords: | ammonia excretion biofertilizer cyanobacteria immobilization nitrogenase activity polyurethane foam rice sugarcane bagasse |
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