(The Gist of Kurukshetra)
BIOFERTILIZERS AND GREEN MANURING
BIOFERTILIZERS AND GREEN MANURING
- The need for sustainable and ecological agriculture is increasingly felt
in the country. Simply stating, organic farming is a production system which
favours maximum use of organic material (crop residues, animal excreta,
legumes, on and off-farm organic wastes, growth regulators, biofertilizers,
biopesticides etc.) and discourages the use of chemical agro-inputs, for
maintaining soil productivity and fertility and pest management under
conditions of sustainable natural resources and healthy environment.
Biofertilizers and green manures are important pillars of organic farming
that support higher yield and maintain soil health. Biofertilizers is a very
cost-effective solution for providing nutrients to crops in a sustainable
manner, unlike chemical fertilizers which are costly and need repeated
application. Similarly, green manuring utilizes lean period between two main
crops and improve soil fertility by providing fixed nitrogen and improving
organic matter of the soil.
- Biofertilizers are products of beneficial microorganisms which increase
agricultural production by way of nutrient supply especially nitrogen and
phosphorus. Biofertilizers can fix atmospheric nitrogen for plant use and
can mobilize unavailable phosphorous pool which can be used by plants. These
biofertilizers are inexpensive, simple to use and have no problem of
environmental pollution. Use of biofertilizers not only help in sustaining
productivity and soil health but also in reducing subsidy burden on the
government by reducing the consumption of chemical fertilizers.
Types of Biofertilizers
- Nitrogen-fixing Biofertilizers: Only a few prokaryotic microorganisms
fix nitrogen directly through a biological process. The organisms thatfix
atmospheric nitrogen are broadly grouped as symbiotic
andnon-symbioticorfree-living organisms. The symbiotic nitrogen fixers
undertake the fixation in the association of plants whereas nonsymbiotic
organisms do not require any association.
- Rhizobium inoculants establish a symbiotic association with pulses,
leguminous oil-seed and fodder crops. Many species of family Rhlzobiaceae
like Rhizobium, Mesorhizobium, Bradyrhizobium, Sinorhizobium and
Azorhizobium are known to fix N in different crops.
- Azotobacter is free-living nitrogen fixing bacteria and unlike Rhizobia
do not require any living host to fix N, Azotobacter chroococcum is the most
abundant species of genus Azotobacter. Azospirillum: It is also a
non-symbiotic, most abundantly found in association with the roots of
millets and grasses. Azospirillum brasiiense, A, lipoferum, A. omazonense,
A. halopraeferens and A. irakense are most commonly used species of this
genus for inoculation.
- Blue Green Algae (BGA): BGA belong to a class of prokaryotic
photosynthetic microorganisms also known, as cyanobacteria are capable of
fixing atmospheric nitrogen aerobically in rice fields. Most commonly found
blue-green algae in Indian rice fields Anabaena, Nostoc, Cylindrospermum,
Calothrix, Scytonema, Toiypothnx, etc. Phosphate,Potassium and Zinc
solubilizing microorganisms: Phosphorus and Potash, both native in soil and
applied as inorganic fertilizers become mostly unavailable to crops because
of its low level of
solubility and immobilization in the soil. A large number of autotrophic and
heterotrophic soil microorganisms have the capacity to solubilize/mobilize
minerals of P and K.Similarly, Zinc is also present in soil but in an
unavailable form. These microorganisms are known to dissolve P, K and Zn by
the production of an organic acid.
The research on KMB and ZSB is at an early stage and only a few KMB
formulations are available in the market all over the world.
Arbuscular Mycorrhizae (AM): AM which was earlier
known as VAM (Vesicular Arbuscular Mycorrhizae) is an obligate symbiont and
are known to improve plant growth due to the improved mobilization of
phosphorus and micronutrients such as zinc and copper and also increases
absorption of water.
Plant Growth Promoting Rhizobacteria (PGPR) PGPR is a
group of beneficial bacteria that improve plant growth by the production of
plant hormones, such as auxins, gibberellins and cytokinins, or by providing
biologically fixed nitrogen. These PGPR also suppress the bacterial, fungal
and nematode pathogens by the production of siderophores,HCN,ammonia,
antibiotics,volatile metabolites , etc.
Azolla Azolla is a free-floating water fern which in
symbiotic association with Anabaena azollae contributes 40-60 kg N per
hectare per crop. The important factor in using Azollo as a biofertilizer
for paddy is its quick decomposition in soil and efficient availability of
its nitrogen to the crop. Its application improves soil physicochemical
properties apart from fertilizer use efficiency. Biofertilizers can also be
classified into two different categories based on the type of formulation.
Carrier-based formulations: For bacterial biofertilizers, may be peat,
lignite, peatsoil, humus, talc. For mycorrhizal inoculants, the base
material be fine powder/ tablets/granules/root biomass mixed with the
growing substrate. For the application of carrier-based formulation, the
seed has to be treated with some sticky liquid like jaggery solution.
- Liquid formulations are available for all bacterial biofertilizers.
Liquid formulations are prepared by mixing bacteria with additives,
stabilizers nutrient solution that support bacterial population for a longer
period. The main advantages of liquid formulations are (a) they are easy to
apply be directly applied to seed (b) they are and as they can be stored for
a longer period (c) they require smaller space for storage compared to
carrier-based can formulations.
Benefits of applications of different biofertflizers Bioferblizers help in
different ways to increase the crop yields some of which are:
- Biofertilizers provide various nutrients to plants like N, P, K, etc.
either by fixing the elemental form (N) or by solubilizing the unavailable
nutrients like P, K and Zinc, VAM (AM) fungi benefit plants by mobilizing
the nutrients from a larger root area. Azolla not only fixes N but also add
organic matter to the soil.
- Biofertilizers not only provide nutrients to plants but also protect
plants from plant diseases as they secrete many antibiotic compounds which
suppress the growth of disease-causing pathogens.
- Besides providing nutrients and suppressing diseases, bio-fertilizers
also secrete some plant growth promoting hormones like auxins and
gibbereilic add which makes plant healthy.
- Many bio-fertilizers like VAM and PGPR also help plants in avoiding
water stress by secreting some polysaccharide which helps in soil
aggregation and conserving moisture for longer times.
- Once the bio-fertilizers are established in the field after 2-3 years of
continuous application, the dose of bio-fertilizers may be reduced.
Availability of inoculants: Rhizobium, Azotobacter, Azospiriilum and PSB
inoculants of popular brands of various companies and corporations (fFFCO,
NFL, Kribhco) are generally available on their agency shops, seed, pesticide
and fertilizer retail shops in the market. All State Agriculture
Departments, research institutes like IARI, NCOF and agricultural
universities also make them available during the season. Many private
companies are also coming up in the production of bio-fertilizers,
especially liquid inoculants.
Method of application of Biofertilizers:
- The success of any biofertilizer organism depends on how close the
organism is applied to seed, seedling or other planting material. Nearer the
organism and planting material, the results in all probability would be
positive. Seed application with bacterial inoculant is the most common
practice of inoculation. Seeds should be sown as soon as possible after
treating with cultures or inoculants to take the full benefit of the same.
Constraints Biofertilizers are the most important source of nutrients in
organic farming but farmers are not able to practice crop inoculation due to
Some of the difficulties faced by the government andextension agencies
inpopularizing the biofertilizers especially for organic farming are:
- The foremost constraint in the popularization of biofertilizers in the
country is the timely supply of cultures in remote corners of the country
where organic agriculture is practiced.
- Lack of knowledge of the farmers about these biofertilizers and proper
measures taken by the extension departments in demonstrating the benefits of
inoculants to farmers.
- Though mechanisms exist under Fertilizer Control Order (FCO 1985) to
looks after the quality control of biofertilizers, the persons involved in
the quality control are not versed with the proper tools and techniques of
handling biofertilizers samples.
- Green manuring-a practice of ancient origin- can be defined as a
practice of ploughing or turning into the soil undecomposed green plant
tissues grown in-situ or cut and brought in for incorporation for the
purpose of improving physical structure as well as the fertility of the
soil. In another way, green manuring is the practice of growing lush plants
on the site into which you want to incorporate organic matter, then turning
into the soil while it is still fresh.
- The plant material used in this way is called green manure. Green
manuring is usually done in the lean period available between the two main
crops. However it can be practiced in between crop rows eg. in-situ green
manuring of Sunnhemp Sesbaniain between maize rows. Kind of green manuring:
Green manuring can be broadly divided into two classes based on the basis of
the cultivation method.
- In-situ green manuring: Green manure crops are grown in the desired
field and buried in the same field for green manuring. An ideal in- situ
green manure crop should be fast growing with minimum nutrient and water
requirements. Nitrogen-fixing legumes which produce heavy tender growth
early in its life cycle are most suitable for green manuring.
- Green leaf manuring: In green leaf manuring, leaves and tender green
twigs are grown in separate fields, bunds or wastelands and incorporated in
the soil of some other field. Advantages of the Green manuring
Following are some of the advantages of the green manuring:
- Following degradation, it adds organic matter to the soil which helps in
maintaining the activity of the beneficial soil microorganisms.
- The green manuring crops improve the physical humus and structure of the
soil by increasing content of the soil. Increase in the water holding
organic matter organic matter also improves capacity of soil thus reducing
the run-off and soil erosion.
- Leguminous green manuring crops like dhaincha, add nitrogen to the soil
for the succeeding crop besides increasing the availability of
nutrients like phosphorus, potassium,calcium, magnesium and iron.
Disadvantages of the green manuring under organic farming:
Following are some of the disadvantages of green manuring:
- If not properly decomposed, the green crop may hamper the germination
and growth of subsequent crops by immobilization of plant nutrients.
Decomposition is not proper especially under rainfed conditions in the
absence of good rainfall.
- An increase of diseases, insects and nematodes is possible if the green
manure crop is not properly decomposed before sowing of next crop.
- Biofertilizers and green manuring are important sources of
nutrients and organic matter respectively for sustaining the crop yields,
especially under organic farming practice .
- Though both biofertilizers and green manuring are old and
established technologies many farmers are not aware of the benefits of these
technologies. Extension workers should train more farmers about the proper
use of biofertilizers for maximum benefits.
- Timely availability of quality biofertilizers and green manure
crop seeds can help in meeting the demands of organic producers especially
in distant areas.
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