Cyanobacteria (blue-green algae) are the most widely distributed algal organisms especially in tropical countries. They are ubiquitous and cosmopolitan found in eutrophic (organically rich) benthos of lakes, ponds, tanks etc. the BGA are the only organisms that grow in adverse and harsh environmental conditions. The global natural resources and energy crisis have widened the gap between demand and supply of nitrogen fertilizer. These blue-green algae plays a significant role in filling this gap. Cyanobacterial biofertilizer giving high yield varieties has further increased the demand of important crops.
DOMINANT BGA IN RICE FIELD:
Rice cultivation is an age-old practice in our country. The average production is only about 1.7 t/ha because more than 85% of total area of rice is owned by small and marginal farmers. These farmers cannot afford to use various inputs needed to harvest maximum yield of rice. In this context, the nitrogen fixing blue-green algae deserve special mention. They are blessing for local farmers. These algae grow luxuriously in tropical habitats. In India, there are natural predominancy of BGA except in acidic soils of Kerala, Assam and parts of Tamil Nadu. Forms like Anabaena, Nostoc, Calothnx, Aulosira, Mastigocladae were found to be widely distributed throughout rice growing tracts of Jharkhand, Bihar and Uttar Pradesh. Experiments conducted with Tolypothnx and Aulosira have shown that the yield of paddy is substantially increased following the inoculation of fields with these algae.
TECHNIQUE FOR GROWTH OF BGA:
There are different techniques for growth of BGA. These algae in general prefer alkaline Ph; water logging and high humidity coupled with high temperature can successfully grow in alkaline wastelands during the summer and monsoons when all these requirements are satisfied. First technique is reclamation experiment, in which their wasteland enclosed by a 0.5m earth embankment, so as to encourage water logging during the rain. This results in increase in nitrogen matter content and decrease in pH, after a few weeks a good growth of BGA has occurred. In another technique, BGA are seeded in shallow tanks and grow under natural environmental conditions. They are ready to use after 2 to 3 weeks. Azolla-Anabaena technique is another process for best growth of BGA.
The propagation of BGA not only enrich the nitrogen status of soil by their fixation process but also provide organic matter and biological patent substances for plant growth. These algae form a living constituent of soil biotype, continue their activity year after year, producing surface humus after death and exert a solvent action on certain minerals maintaining a reserve supply of element. So, cyanobacteria play an important role in maintenance and build-up of soil fertility, consequently increasing rice growth and yield a natural biofertilizer.
By: Dr. Arpana Sharma (guest faculty, RKMVU,Ranchi)