# A lecture on Biofertilizers - Introduction, status and scope

Ajeet Kumar

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Ajeet Kumar. A lecture on Biofertilizers - Introduction, status and scope. Master. Biopesticide and Biofertilizer (Elective course), Dr. Rajendra Prasad Central Agricultural University, Samastipur, India. 2025, pp.1-7. [hal-05266999](https://hal.science/hal-05266999v1)

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Dr. Rajendra Prasad Central Agricultural University

Pusa (Samastipur) - 848125, Bihar

A lecture notes

On

Biofertilizers - Introduction, status and scope

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COURSE TITLE: Biopesticide and Biofertilizer

*(Elective course)

COURSE NO.: ASS-307

CREDIT HOUR: 3 (2+1)

Dr. AJEET KUMAR

Assistant Professor-cum-Scientist (Soil Science)

Department of Microbiology

Collage of Basic Sciences and Humanities, Dr. RPCAU, Pusa

2025
# Biofertilizers - Introduction, status and scope

Dr. AJEET KUMAR<fnref n="1" />

## Introduction

Indian economy is an agrarian economy, a reason that makes biofertilizers an essential need for Indian farmers. Though most of our agricultural activities are dependent on monsoon, the use of a good biofertilizer can yield a better crop to the farmers and increase the fertility of the soil. According to an estimate 240 million tons of food grains will be required to feed about one billion expected populations by 2000 AD in India and to achieve this milestone, a sizable quantity of mineral fertilizer will be required. The total fertilizer requirements of our country would be 23 million tonnes as against the present consumption level of 13 million tonnes, which is beyond any single type of nutrient source to accept the challenge of appropriate nutrient supply. Integrated use of all the sources such as mineral fertilizers, organic manures, biofertilizers etc. is the only alternate for improving soil fertility. It has now become possible to meet a large part of our total nitrogen demand through proper husbandry of biological nitrogen fixation by micro-organism in crop production system. Biofertilizers are capable of providing an economically liable level for achieving the ultimate goal of enhanced productivity. The crop microbial soil ecosystem can, therefore, be energized in sustainable agriculture.

India is fourth largest user of chemical fertilizers (12.5 million tonnes of NPK nutrients) in the world even its soils are still being depleted of their inherent nutrients reserve as a result of wide gap between additions (12.5 million tonnes) and removal (18.5 million tonnes). One tone of produce removes an average of 32 kg nitrogen, 12 kg phosphorus and 58 kg potash. The strategy for sustaining satisfactory yield levels envisages nutrient balance and efficient nutrient cycling. This can be successfully achieved through integrated use of mineral fertilizer, bulky organic manures, compost, green manure, biological inoculant etc. At present, the nutrient use in India is much less compared to that of other countries. Against world average consumption of 95 kg ha⁻<fnref n="1" />, and we are using 74 kg ha⁻<fnref n="1" /> with national productivity level of merely 1.1 metric ton per hectare. At present India produces about 117 million metric tonnes of food grain for its growing population of more than 800 million people. Nitrogen fertilizer plays prominent role in increasing this food requirement. At present the vast gap cannot be filled up merely through the production of synthetic nitrogen

<footnote n="1">¹Assistant Professor-cum-Scientist (Soil Science-Soil Microbiology, Soil fertility, Soil Chemistry), Department of Microbiology, College of Basic Sciences & Humanities (CBS&H), RPCAU, Pusa-848125, Bihar. E-mail: ajeet.sri@rpcau.ac.in</footnote>
fertilizers due to scarcity of high cost of raw materials such as fossil fuels. Biological nitrogen fixation is the key to sustain agriculture productivity application of biofertilizer in the field is the liable alternative. In fertilizer manufacturing factories, nitrogen is fixed industrially, by means of the Haber Bosch process requiring $H_2$ gas, very high temperature and enormous energy. Industrially fixed nitrogen has been used precipitously. It was produced 4.0 lakh metric tones in 1905 and this was increased to 3.5 million tones of nitrogen fertilizer. However, above every hectare of land, there are 78,000 tonnes of inert nitrogen gas ($N_2$). As nitrogen is the most limiting nutrient for increasing crop productivity. Only a few prokaryotic organisms are able to fix nitrogen directly through a biological process. Annual biological nitrogen fixation (BNF) is estimated to be around 175 million tonnes of which close to 79 % is accounted for by terrestrial fixation

The term biofertilizers or which can be more appropriately called ‘microbial inoculants’ can be generally defined as a preparation containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulytic microorganisms used for application of seed, soil or composting areas with the objective of increasing the number of such microorganisms and accelerate certain microbial process to argument the extent of the availability of nutrients in a form which can be easily assimilated by plant. In large sense, the term may be used to include all organic resources for plant growth, which are rendered in an available form for plant absorption through microorganisms or plant associations or interactions. Soil harbours a range of microorganisms, which bring about a number of biochemical reactions in soil. The soil organisms are classified into two broad groups i.e. soil flora and soil fauna, they are again subdivided, depending upon their size such as micro and macro flora. Soil microflora includes bacteria, fungi, actinomycetes, algae etc. of these groups, bacteria are the most abundant followed by actinomycetes and fungi; algae are found under specific situation. The biomass and population of these micro-organisms in soil have been given in Table 1.

<table><thead><tr><td>Sr. No</td><td>Microorganism</td><td>Average number (in lakhs) per g of soil</td><td>Average biomass (in kg per ha)</td></tr></thead><tbody><tr><td>1.</td><td>Bacteria</td><td>1000</td><td>500</td></tr><tr><td>2.</td><td>Fungi</td><td>10</td><td>1000</td></tr><tr><td>3.</td><td>Actinomycetes</td><td>100</td><td>750</td></tr></tbody></table>
<table><tr><td>4.</td><td>Algae</td><td>0.01</td><td>150</td></tr></table>

The presence of these microorganisms make the soil a living and active system. These microorganisms play a significant role in the life cycle of plants and animals through a number of process such as decomposition, solubilization, nutrient fixation and supply of plants. At present, in India there is a gap of about 10 million tonnes of plant nutrients between removal by crops and replenishment through fertilizers. Supply of nutrients from organic manure has not so far been able to fill up this gap and also in years to come nutrient supply from the source is unlikely to improve due to competitive demand for alternate uses like fuel and fodder. Of late, biofertilizer are being promoted as an important component in supplementing plant nutrient need of the country. India is one of the important countries in biofertilizer production and consumption in the world. The present production capacity of different production units in the country is about 4500 tonnes per annum. The maximum production capacity is in Agro Industries Corporation followed by State Agriculture Departments, National Biofertilizer Development Centre, State Agriculture Universities and private sector. Among the different states, the maximum production capacity is in Tamil Nadu followed by M.P. U.P., Gujarat and Maharashtra.

## Thrust in Research and Development:

The rising cost of chemically fixed nitrogen fertilizer and the massive inputs of non renewable resource will be devastating. As an alternative there is urgency of major research effort in biological nitrogen fixation. Nitrogen in the form of ammonia is used by plants and microbes as a building block for the synthesis of amino acids and of other nitrogenous compounds. The conversion of atmospheric Nitrogen into ammonia by the nitrogen fixing microbes, mostly certain bacteria and blue green algae is called biological nitrogen fixation. Although leguminous plants have been used extensively in agriculture for centuries, it is possible to exploit these nitrogen fixing plants meaningfully. The use of new leguminous crops as well as the breeding of more vigorous and effective traditional leguminous crops can be helpful in food production. As the bacteria are the agents of fixation in bacterial plant Rhizobial technology and soil microbiology are the neglected areas. It would be a right type technology that all farmers could use legume - Rhizobial combinations constitute, a built-in nitrogen source for food crop production. Approximately 75 per cent of the nitrogen utilized by legume comes from the soil, with only 25 per cent from BNF. It is necessary to increase the rate of nitrogen fixation achieved, which would have a multiplier effect on the enhancement of crop productivity. Chemical fertilizers have temporary effect while
biofertilizers have permanent effect without any production problem. Use of composite biofertilizers have permanent effect without any production problem. Use of composite biofertilizers can increase soil fertility. The cost is too much low for the biofertilizers and its proper use dose not only include a correct application of the inoculant to the seed soil but also good. Considering the prospects of biofertilizers in the country, the biofertilizers development centres are being established both in government and private sectors and It is only possible by establishing joint venture in biofertilizer agro based industry.

Biofertilizers are products that contain microorganisms essential for soil fertility and plant growth when added to the soil. A biofertilizer is a chemical that contains living microorganisms that colonize the rhizosphere or the interior of the plant when given to seeds, plant surfaces, or soil, and encourage growth by controlling the quantity or availability of primary nutrients to the plant host. Biofertilizers supply nutrients to plants through natural processes such as nitrogen fixation, phosphorus solubilization, and the creation of growth-promoting chemicals. They help restore the soil's natural nutrient cycle and increase soil organic matter. Healthy plants can be developed with the application of biofertilizers while also improving the soil's sustainability and health. Biofertilizers will likely decrease the need for synthetic fertilizers and pesticides, but they will not be able to completely replace them.

## Importance of Biofertilizers

There are various uses of biofertilizers that prove their importance. They include – improving the soil quality, protecting the plants from pathogens, avoiding environmental pollution, destruction of harmful substances present in the soil, etc. Thus, biofertilizers are very important.

## Types of Biofertilizers

### 1. Symbiotic Nitrogen-Fixing Bacteria

The symbiotic nitrogen-fixing bacteria like Rhizobium get food and shelter from the plants and provide them with fixed nitrogen in return. One of the most important symbiotic nitrogen-fixing bacteria is Rhizobium. Bacteria seek shelter and food from plants here. In exchange, they assist the plants by delivering free nitrogen.

### 2. A Loose Association of Nitrogen-Fixing Bacteria

Some bacteria aren't related directly with the plants but live around them For example, A nitrogen-fixing bacterium called Azospirillum lives near the roots of higher plants but does not form a close bond with them. This is known as rhizosphere association because these bacteria collect plant exudate and use it as food. Associative mutualism is the name given to this phenomenon.
**3. Symbiotic Nitrogen-Fixing Cyanobacteria**

There are many symbiotic nitrogen-fixing cyanobacteria like liverworts, cycad roots, the bacteria released by fern plant decay, etc. Cyanobacteria or blue-green algae from a symbiotic relationship with numerous plants. Anabaena can be found in the fern's leaf cavities. It's in charge of nitrogen fixation. The fern plants decompose and release nutrients for the rice plants to use. Azolla pinnata is a fern that grows in rice fields, however, it has no effect on the plant's growth.

**4. Free-Living Nitrogen-Fixing Bacteria**

Free-living bacteria are found in soil, and they also perform nitrogen fixation. These include clostridium, azotobacter, and bacillus polymyxin. They are nitrogen-fixing bacteria that live in free-living soil. Clostridium beijerinckii, Azotobacter, and other saprotrophic anaerobes are among them. Rhizobium and Azospirillum are the most extensively utilized forms of biofertilisers.

**Components of Biofertilisers**

The components of a biofertilizer are:

1. **Bio Compost:**

It is eco-friendly and is produced from waste products coming from sugar industry. It also includes bacteria, fungi, and some plants.

2. **Tricho-Card:**

This eco-friendly non-pathogenic product is useful for many crops and plants, as it plays the role of a productive destroyer against the items that are harmful to the crop.

3. **Azotobacter:**

It plays an important role in atmospheric nitrogen fixation and protects the plant roots from pathogens in the soil.

4. **Phosphorus:**

To settle the exact level of need for nitrogen for a plant, and to determine the nitrogen level of the soil, phosphorus fertilizers are very helpful.

5. **Vermicompost:**

Known for quickly improving soil fertility, these are probably the most eco-friendly fertilizers that contain vitamins, sulphur, hormones, organic carbon, and antibiotics required for the growth of the plant.

**Applications of Biofertilizers**

These are some important applications of biofertilizers:
1. **Seedling Root Dip:** Used for rice crops, the seedlings are planted in a waterbed for 8 to 10 hours, in this method.

2. **Seed Treatment:** In this process, the seeds are dipped in nitrogen-phosphorus mixed fertilizers. After drying them, they are planted as early as possible.

3. **Soil Treatment:** The mixture of biofertilisers and compost fertilizers is kept overnight and spread over the soil the next day. This treatment takes place before sowing the seeds.

## Disadvantages of Fertilisers

* Chemical fertilizers are supplemented by biofertilizers, not substituted for them.

* Biofertilizers only improve crop productivity by 20 to 30 percent. Unlike chemical fertilizers, they do not result in a significant improvement in productivity.

* For specific crops, specific fertilizers are necessary. This is more applicable to microorganisms that live in a symbiotic relationship. If non-specific Rhizobium is applied as a fertilizer, root nodulation, and crop production will not rise.

* Strict aseptic precautions are required during the manufacture of microbial fertilizer. During microbial mass manufacturing, contamination is a common problem.

* Microbes are killed when exposed to sunlight for an extended period of time because they are light-sensitive.

* When stored at room temperature, microbial fertilizers must be used within six months, and when stored at chilling temperature, it must be used within two years