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.
CONCLUSION:
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)
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