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Bio-reactors to Bio-fertilizers

Updated: Dec 28, 2021


After the green revolution, India is a self-sufficient country which in fact, has exported surplus to the other countries. For many years India has been known for farming and agriculture. Agriculture is a means of livelihood also the nation depends on it.

According to the country's population growth, food demands are increasing, and demolishing of farming sectors and the increment in urbanization have led people to think on this matter. Earlier everyone was dependent on weather and monsoons for cultivation purposes but, now things have changed as many factors are involved in the growth of crops/plants. Agriculture contributes 17.1% to the country’s Gross Value Added and 54.6% of the population is engaged in agriculture and allied activities. Advanced technologies, equipment, irrigation facilities, genetic engineering have made efforts in establishing and developing this sector but, one of the factors that have more impact is fertilizers. According to annual report 2019-2020, fertilizers are expected to play a key role in increasing the average crop yield per hectare, despite this, the use of fertilizer in India is lower than the other emerging and developed countries.


  • Soil fertility- Soil is the most important natural resource. The soil of a cultivation land should be fertile, able to provide all nutrients in adequate amount and mechanical strength for plants. Plants use inorganic minerals for nutrition, some nutrition is provided by air and water like carbon(C), hydrogen(H), and oxygen(O) whereas other essential elements like nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) are required in trace amount are provided by supplements/fertilizers. So, the capacity of soil to provide all the above nutrients in proportion quantities is called soil fertility. Mineral matter, air, water, and organic constituents are responsible for different forms of soil. soil containing less than 0.5% organic matter is described as poor soil and matter ranging 1.5% with pH 6.5-7.5 is considered as intermediate/neutral soil. Without these elements, plants will display abnormalities of growth, deficiency symptoms, or may not reproduce normally. If crops are cultivated without fortification of soil, fertility is compromised. To protect soil fertility and provide essential nutrients, the addition of animal manure, fertilizers is essential.

  • Fertilizers- A synthetic man-made material consists of chemicals like urea, ammonium phosphate, and muriate which act as a stimulant to supply plant nutrients essential for the development or growth of plants. They are nutrient specific, easily soluble in water, and enhance plant metabolism. But, when plants are washed away with water synthetic fertilizers pollute surroundings, reduce soil fertility making it too acidic or alkaline, and harm organisms present in soil and humans affecting lungs and bronchi. This is why farmers have shifted from chemically synthesized fertilizers to BIO-FERTILIZERS.

BIOFERTILIZERS- Fertilizers made from biological organisms are called Biofertilizers. These are substances that contain microbes which when added to the soil increase its fertility and promote plant growth. Living organisms present as biofertilizers fix atmospheric nitrogen and enrich the soil with other nutrients as well.

  • Symbiosis relationship- The relationship in which two organisms are benefitted from each other is known as a symbiosis relationship. In the case of plants and microbes, plants give nutrients to microbes as their food, and microbes in return fix atmospheric nitrogen for them to enrich the soil for plant growth.

  • Leguminous plants- in natural conditions or environment, organisms that can fix atmospheric nitrogen are present only to certain plant roots. Not all plants have nitrogen-fixing organisms. The plants having specific nitrogen-fixing microbes in their roots are called leguminous plants (eg., pulses, groundnut, soybeans) and the ones who have nitrogen-fixing microbes other than microbes present in leguminous plants in their roots are called Non-leguminous plants (maize, barley, oats, sorghum, millet, Sugarcane, rice).

NITROGEN FIXING ORGANISMS- Nitrogen is an essential part of a living organism as it is present in the nucleus of each cell. In a natural phenomenon, nitrogen is present in the atmosphere which is 78% of the atmosphere, and cannot be consumed in this state. The process to fix and convert this atmospheric nitrogen to reactive nitrogen compounds like nitrates, nitrites, and ammonia is known as the nitrogen-fixing mechanism. Under ordinary conditions, nitrogen does not react with other elements. Nitrogen into different compounds can be fixed by lightening, ultraviolet rays, and micro-organisms. Other than Bacteria following microbes can also be used for nitrogen fixation:

  • Algal Biofertilizers: e.g. Blue Green Algae (BGA) and Azolla

  • Actinomycetes Biofertilizer: e.g. Frankia

  • Fungal Biofertilizers: e.g. Mycorrhiza

The table below can show several bacteria and cyanobacteria helpful to the plants:

PRODUCTION AND DEVELOPMENT OF BIOFERTILIZERS- Preparations in the production of biofertilizers need dormant strains of microbes (in-active metabolically), which can positively impact soil rhizosphere and helps in plant development and growth.

inoculum is formed by inoculating isolated strain in a small flask containing a specific medium. Further, the inoculum is added to the production medium as a bio-inoculant. Recovery of these selected strains is done after they have reached the exponential phase during fermentation occurring in large fermenters. Eventually, they are either coated as seed (embedded form) or can use directly as a sugary syrup slurry.


  • Seed pelleting- Seed coating has been widely used in agriculture as an effective means to alleviate biotic and abiotic stresses, thus enhancing crop growth, yield, and health. Plant growth-promoting microorganisms (PGPM) are recognized as essential contributors to improving agricultural productivity via direct application to the rhizosphere and plant tissues, or seed inoculation. Calcium carbonate is mostly used as the last step of seed pelleting processes in biofertilizers. It is used to stimulate root nodules in the roots of plants necessary to fulfill the plant's nitrogen requirements.

  • Inoculant carriers- As the name suggests, they contain both starter culture and carrier material. Usually, Peat is used as carrier material as it has the ideal property to prolong the growth of microbial strains. The other alternative carriers like lignite, coal, charcoal, vermiculite, polyacrylamide, etc. are substitutes but do not enhance strain properties. So, an ideal carrier should:

  1. be non-toxic

  2. have a good moisture absorption capacity

  3. be free of lump forming material

  4. be easy to sterilize

  5. be inexpensive

  6. be easily available

  7. have the good buffering capacity

  • Liquid biofertilizers- These are suspensions or blends having nitrogen-fixing bacteria making them more available to plants. They solubilize in soil easily due to their watery property and are eco-friendly comparable to chemical fertilizers ultimately escalating plant growth and yield. They are cost-effective and easy to apply. Examples are Zinc solubilizing bio-fertilizers (ZSB), Potassium mobilizing bio-fertilizers (KMB), Phosphorus solubilizing bacteria (PSB).


  • Biofertilizers not only helps fixing nitrogen in the soil but also solubilize insoluble forms of phosphates, iron, aluminum into usable compounds.

  • They contain metabolites that can stimulate hormones to promote root growth.

  • For leguminous plants, non-leguminous plants to normal crops, Biofertilizers can be used for plant growth by initiating root nodule mechanisms.

  • They decompose organic matter and help in mineralization in soil.

  • Improve yield by 30-40% of production rate.

CONCLUSION- According to the modern-day economic scenario, it is our duty to uplift agriculture practices. The growing population demands an elevation in food requirements and biofertilizers are vital for sustainable development. Biofertilizers help in the maintenance of soil fertility and benefits plants for their growth and development by fixing atmospheric nitrogen to available soluble forms. It acts as manure for many crops and has somewhat replaced chemical fertilizers. It is eco-friendly, economical, and non-toxic without any side effects.

*REFRENCES- NABARD knowledge bank, Vikaspedia, Annual report of biofertilizers (2019-2020)

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