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A Recent Study on Nitrogen Fixing Blue-green Algae

M. A. Hashem
Department of Soil Science, Bangladesh Agricultural University, Mymensingh.

B. K. Biswas
Department of Soil Science, Bangladesh Agricultural University, Mymensingh.

N. A. Banu
Department of Soil Science, Bangladesh Agricultural University, Mymensingh.

M. A. Rahman
Department of Soil Science, Bangladesh Agricultural University, Mymensingh.

M. R. Islam
Department of Soil Science, Bangladesh Agricultural University, Mymensingh.

Abstract/ Executive Summary:

With a view to finding out the effective strains of nitrogen fixing blue-green algae (BGA) for the production of biofertilizer for rice cultivation in Bangladesh agriculture, a study was carried out on 10 AEZ covering 23 locations of rice field. Both nitrogen fixing and non-nitrogen fixing blue- green algae were present in all soils studied but their population was highly variable. Higher population of BGA was associated with soils having higher organic matter and phosphorus status. Although the population was higher in the surface soil (0-0.5 cm) but they were also present upto 5- 15 cm soil depth. A total of 52 taxa of BGA belonging to Anabaena, Nostoc, Scytonema, Calothrix, Tolypothrix, Phormidium, Lyngbya, Fischerella, Anabaenopsis, Chlorogloea, Westiellopsis, Oscillatoria, Nostochopsis and Hapalosiphon was brought under unialgal culture. Among the various strains studied Nostoc, Anabaena, Scytonema, Calothrix, Fischerella and Hapalosiphon were found to be the dominant forms in soils. A marked variation was observed in growth and nitrogen fixation among the different genera as well as different species of a particular genus. Differences also were naticed in response of blue-green algae with respect to salinity tolerance. Some of the strains were initially selected with respect to growth and nitrogen fixation in batch culture.

Keywords: Nitrogen fixing, Algae, Biofertilizer

Location: Bangladesh Agricultural University, Mymensingh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Bio fertilizer

Objectives:

To screening and selection of promising nitrogen fixing strains of blue-green algae from rice fields of different AEZ for their subsequent use as biofertilizer,

Methodology:

Ten AEZ, covering major regions of Bangladesh, having deistinct different soil types, have been selected for the study, Blue-green algal strains were isolated from 23 rice growing areas located in the selected AEZ. Soils were collected from 0-15 cm depth of 13 rice fields in the selected areas. Dilution series from 10^-1 to 10^-9 were made and 10 tubes containing Chu 10D-N medium were inoculated with 1 ml portion of each soil dilution. The tubes were incubated for 30 days at 30? under the light of 100-watt bulbs fixed at 20 cm apart and 50 cm from the tubes. The surface of the tubes for algal growth visible to the naked eye was observed 30 days after incubation. The number of tubes showing positive growth was recorded and the readings were converted to most probable number of blue-green algae following the probability table for determination of abundance of organisms in soil. Cells of blue-green algae, grown in the tast tubes, were picked up with the aid of platinum loop, distributed over the surface of the solidified agar, and incubated under light. It was rendered unialgal by picking single hormogonium by sterile needles with the help of microscope. BGA were grown in liquid medium and finally checked during late exponential phase with contrast microscope. The blue-green algal strains have been identified on the basis of their morphological characters under direct microscopic examinant. BGA were grown in Chu 10 D-N growth medium under light arrangement mentioned earlier at 30?. For heterotrophic growth, medium was supplemented with 20 mM glucose and sucrose, added after autoclaving and incubated in the dark. BGA cultures were inoculated in N free medium and incubated under light and temperature as stated above. Soils were analysed for p^H, texture, organic carbon, total nitrogen, available phosphorus, sulphur, exchangeable potassium, calcium and sodium, electrical conductivity and cation exchange capacity following standard methods.

Source of Information: Proceedings of Inter-congress Conference of Commission IV "Improving soil Management for Intensive Cropping in the Tropics and Sub-tropics", pp-375-385, Dhaka, Bangladesh

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the results, it appears that all the strains studied had the capacity to reduce the EC of the growth medium at a substantial rate and for some strains the salinity levels reduced nearly 50%. The present study indicates that BGA might have the reclamative ability but for confirmation further study is essential. From this study, twelve strains among which five strains of Nostoc, one Anabaenopsis, one Anabaena one Scytonema, one Calothrix, one Chlorogloea, one Fischerella and one Hapalosiphon were initially selected for their use as biofertilizer.

Knowledge Management: Journal