(The Gist of Kurukshetra) BIOFERTILIZERS AND GREEN MANURING [MAY-2019]
(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 various reasons.
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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