Biofertilizers
One
of the major concerns in today's world is the pollution and contamination of
soil. The use of chemical fertilizers and pesticides has caused tremendous harm
to the environment. An answer to this is the biofertilizer, an environmentally
friendly fertilizer now used in most countries. Biofertilizers are organisms
that enrich the nutrient quality of soil. The main sources of biofertilizers are
bacteria, fungi, and cynobacteria (blue-green algae). The most striking
relationship that these have with plants is symbiosis, in which the partners
derive benefits from each other.
Plants
have a number of relationships with fungi, bacteria, and algae, the most common
of which are with mycorrhiza, rhizobium, and cyanophyceae. These are known to
deliver a number of benefits including plant nutrition, disease resistance, and
tolerance to adverse soil and climatic conditions. These techniques have proved
to be successful biofertilizers that form a health relationship with the roots.
Biofertilizers
will help solve such problems as increased salinity of the soil and chemical
run-offs from the agricultural fields. Thus, biofertilizers are important if we
are to ensure a healthy future for the generations to come.
Mycorrhiza
Mycorrhizae
are a group of fungi that include a number of types based on the different
structures formed inside or outside the root. These are specific fungi that
match with a number of favourable parameters of the the host plant on which it
grows. This includes soil type, the presence of particular chemicals in the soil
types, and other conditions.
These fungi grow on
the roots of these plants. In fact, seedlings that have mycorrhizal fungi
growing on their roots survive better after transplantation and grow faster. The
fungal symbiont gets shelter and food from the plant which, in turn, acquires an
array of benefits such as better uptake of phosphorus, salinity and drought
tolerance, maintenance of water balance, and overall increase in plant growth
and development.
While
selecting fungi, the right fungi have to be matched with the plant. There are
specific fungi for vegetables, fodder crops, flowers, trees, etc.
Mycorrhizal
fungi can increase the yield of a plot of land by 30%-40%. It can absorb
phosphorus from the soil and pass it on to the plant. Mycorrhizal plants show
higher tolerance to high soil temperatures, various soil- and root-borne
pathogens, and heavy metal toxicity.
Legume-rhizobium
relationship
Leguminous
plants require high quantities of nitrogen compared to other plants. Nitrogen is
an inert gas and its uptake is possible only in fixed form, which is facilitated
by the rhizobium
bacteria present in the nodules of the root system. The bacterium lives in the
soil to form root
nodules (i.e. outgrowth on roots) in plants such as beans, gram, groundnut, and
soybean.
Blue-green algae
Blue-green
algae are considered the simplest, living autotrophic plants, i.e. organisms
capable of building up food materials from inorganic matter. They are
microscopic. Blue-green algae are widely distributed in the aquatic environment.
Some of them are responsible for water blooms in stagnant water. They adapt to
extreme weather conditions and are found in snow and in hot springs, where the
water is 85 �C.
Certain
blue-green algae live intimately with other organisms in a symbiotic
relationship. Some are associated with the fungi in form of lichens. The ability
of blue-green algae tophotosynthesize food and fix atmospheric nitrogen accounts
for their symbiotic associations and also for their presence in paddy fields.
Blue-green
algae are of immense economic value as they add organic matter to the soil and
increase soil fertility. Barren alkaline lands in India have been reclaimed and
made productive by inducing the proper growth of certain blue-green algae.
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