Useful Role of Bacteria in Agriculture: Do you know who is responsible for the decay and decomposition of organic matter? Various bacterias present in soil help in the process of decay or decomposition of organic matter. There are several useful roles of bacteria in agriculture, medicine, food, and many other industries. Bacteria are ubiquitous due to their ability to evolve and survive in all kinds of environments. It is true that they are the main causative agents for a long list of diseases. But, not all bacteria are harmful. They play a crucial role to fulfill a number of our needs, from medicines to food products.

In this article, we are going to learn the useful role of bacteria in agriculture. We will know what soil microbiology is and how it is important in agriculture? And lastly, we will learn some of the important bacterial products used in agriculture.

Soil Microbiology and Agriculture

The soil provides a favourable environment for various microorganisms, including bacteria, fungi, viruses, and protozoa. Therefore, these microbes are abundantly and sometimes densely found in the soil. It is estimated that there are almost one to ten million microorganisms per gram of soil. Among all these microorganisms, bacterias and fungi are the most common. All these microorganisms in the soil interact with each other to create constantly altering conditions. The interactions between these multiple factors are responsible for various types of soil in a particular place and constitute a distinct branch of agriculture microbiology called soil microbiology.

The agricultural industry consists of anything grown or raised for human use, such as livestock, lumber, flowers, and harvesting plants to feed or sell, etc. It is one of the oldest industries in the world, almost thousands of years old. The agricultural industry has changed a lot in the last 100 years. Now, agriculturalists can grow more crops in small spaces. The cost of farming is reduced. Advance study in soil microbiology and biotechnology has brought many changes in agriculture like better quality and quantity crops, improvement in soil fertilisation, etc.

Fig: Soil Microbiology

Role of Bacteria in the Agriculture Field

Microbes, especially bacteria, play a very important role in the agricultural field. Some of the important roles of bacteria in the agriculture field are given below:

1. Decay and decomposition: Bacteria present in soil play an important role in the decay or decomposition of organic matter. They serve a double purpose. Firstly, they act as scavengers by removing harmful substances from the earth. Secondly, they return it to the soil, which is used as nutrients by plants. The dead bodies (of both plants and animals) and waste materials are decomposed by saprophytic bacterias. As a result, the basic elements of the environment that make up their body, like phosphorus, oxygen, hydrogen, and sulphur are returned to their original forms, and nutrient cycles are repeated in the atmosphere.

Fig: Decomposition

2. Soil fertility: Bacterias play an important role in maintaining and increasing soil fertility. The fertility of the soil is always dependent on its nutrient and water content. Due to the continuous absorption of nutrients and water by the growing plants, soil loses its fertility. Bacteria decompose complex organic materials into their simple forms and also produce secondary products that lead to an increase in soil fertility. It also increases the moisture content of the soil. Thus, these bacteria help to increase the amount of nutrients in the soil that are needed by the plants.

3. Nitrogen Fixation: Four-fifths (around 78%) of our atmosphere is nothing but nitrogen, but plants cannot use nitrogen in its elemental form. They use it in the form of nitrates, nitrites, or ammonia from the soil. In nature, a regular supply of nitrogenous salts is ensured by bacteria of certain types, such as ammonifying bacteria, nitrifying bacteria, and nitrogen-fixing bacteria. Ammonifying bacteria are known to release ammonia from protein, e.g., Bacillus vulgaris, B. ramosus, etc. Soil ammonia is trapped as ammonium salts and available for plant absorption. There are two types of nitrifying bacteria in the soil; Nitrite bacteria that convert ammonium nitrogen into nitrites (e.g., Nitrosomonas, Nitrosococcus, etc.), and Nitrate bacteria which transform nitrites into nitrates (e.g., Nitrocystis). The nitrogen-fixing bacteria are unique in tapping the nitrogen source for plants. This transformation of atmospheric nitrogen into nitrogenous compounds that can be used by plants is called nitrogen fixation.

These bacteria maintain a continuous circulation of nitrogen in nature. A series of changes through which nitrogen passes due to the activities of these bacteria constitute the nitrogen cycle.

Fig: Nitrogen Cycle

There are two kinds of nitrogen-fixing bacteria;-living (symbiotic) and mutualistic (non-symbiotic).

a.-living (non-symbiotic) bacteria: These bacteria do not live in symbiotic association with plants. As the name suggests, these are-living. Examples include Azotobacter, Beijerinckia, and Clostridium.

b. Mutualistic (symbiotic) bacteria: Symbiotic bacteria are ones that live in symbiotic association with plants. For example, Rhizobium is associated with leguminous plants.

Some more examples of nitrogen-fixing bacterias are given below:

Name of Bacteria	Place of living	Mode of living
Rhizobium leguminosarum (Rhizobiaceae)	Root nodules of legumes	Symbiotic
Bradyrhizobium japonicum	Root Nodules of Legumes Soybean	Symbiotic
Frankia spp.	Nodules of Casuarina, Alnus, etc.	Symbiotic
Azotobacter agilis	Aerobic and soil-inhabiting	Free-living
Clostridium pneumoniae	Anaerobic and soil-inhabiting	Free-living

Bacterial Products used in Agriculture

In modern agriculture, the utilisation of microbes as natural fertilisers is very common. The harmful impacts and high cost of chemical fertilisers are making them unfit to use. The agricultural productivity of the soil can also be improved by microbes found in the ground soil. Today, we are using naturally occurring microbes to produce biological products that can recycle nutrients and are eco-friendly. Following are some of the important biological products used in agriculture these days:

1. Biofertilizers: Biofertilizers can be defined as substances containing microorganisms that increase the fertility of the soil and promote plant growth by supplying essential nutrients when added to the soil. The main constituents of biofertilizers are living microbial inoculants, including algae, fungi, bacteria alone or in combination. They can enhance the availability of nutrients in the soil for plants. Biofertilizers can convert the nutritionally important component present in the soil from unusable form to usable by their microbial activities, including phosphate solubilisation, nitrogen fixation, excretion of plant growth hormones, and biodegradation. The use of biofertilizers is eco-friendly, productive, easily accessible to marginal farmers, and more efficient.

Fig: Biofertilizers

The bacterias which can be used in the production of biofertilizers are;

a. Rhizobium: These bacteria have the ability to clone in lines of roots of legume plants and can fix much nitrogen. With the quantity of nitrogen they fix, they are the most efficient biofertilizers.

b. Azotobacter:  Other than rhizobium bacteria, azotobacter can also fix nitrogen. Various species of azotobacter are present in the soil and can act as biofertilizers.

c. Cyanobacteria: These bacteria are also called blue-green algae and are found as-living or as symbiotic association with rice crops. These can perform photosynthesis similar to the algae and plants. It can produce the fixed nitrogen at the rate of 20–30 kg per hectare under ideal conditions, and nowadays, it is used as a biofertilizer.

d. Plant Growth-Promoting Rhizobacteria (PGPR): This is one of the beneficial groups of rice bacteria present in the plant’s rhizosphere zone. It analyses the root to improve the plant’s growth by acting as bioprotectant, biostimulant, and biofertilizers.

2. Biopesticides: The soil also has plant pathogenic bacteria present in the rhizospheric zone, and it can cause a lot of diseases in the plant. Using these pathogenic microbes, researchers have made a biological tool to control unwanted weeds and pests called biopesticides. These microbes possess genes that are invasive and can attack the weeds and kill them. For example, the bacterium Bacillus thuringiensis produces toxic proteins that kill certain insects but are harmless to humans. These are being made and marketed as biopesticides. Bacillus popillae (milky spore disease) can kill Japanese beetle larvae.

Fig: Mode of Action of Bacillus thuringiensis

3. Bioinsecticides: Bioinsecticides have been developed to minimise the use of synthetic insecticides by making the use of microorganisms. Because of the shortest shelf life, they do not persist in the environment and are also eco-friendly. For example, 200 diseases are caused by fungi in insects that can control their population. The most widely used Bt insecticides are formulated from Bacillus thuringiensis var. Kurstaki can kill larvae of butterflies and moths. They are also used to control many common leaf-feeding caterpillars.

Fig: Bioinsecticides

4. Green manure: Green manure is produced by leaving uprooted, sown crops and their parts to wither on a field so that they act as a mulch and soil amendment. Heterotrophic bacteria that consume organic matter are used to break down green manure into plant nutrient components. These are added for the purposes such as building soil organic matter and soil structure, supplying nitrogen and other essential nutrients to crops to prevent leaching of soluble nutrients from the soil, preventing damage to soil structure by providing ground cover, etc. Hence, green manures usually perform multiple functions such as soil improvement, soil protection, etc.

5. Biogas: Biogas is an example of renewable fuel obtained by the decomposition of organic matter like plant wastes, food scraps, animal waste, etc. It is actually a mixture of gases released by microorganisms during decomposition. Methane is the primary and main biogas. There are certain bacteria that grow well under anaerobic conditions and produce a large amount of methane along with carbon dioxide and hydrogen. The bacteria that produce the gaseous mixture are called methanogens. Methanobacterium is an example of methanogen. It is found inside the rumen of the cattle and the sludge produced during sewage treatment.

Summary

The science of all these microorganisms present in air, soil, water is also called microbiology. Soil microbiology is one of the branches of microbiology. In soil microbiology, we study the interactions between the multiple factors responsible for various soil types in a particular place. Bacteria play a very important role in the agricultural field. Bacteria help in the decay or decomposition of organic matter in the soil. They can help in increasing soil fertility and also promote plant growth. The nitrogen-fixing bacteria are of two types:-living (non-symbiotic) bacteria (e.g., cyanobacteria) and mutualistic (symbiotic) bacteria (e.g., Rhizobium associated with leguminous plants). Various bacterial products such as biofertilizers, biopesticides, and bioinsecticides are also used in agriculture instead of chemical products.

Frequently Asked Questions (FAQs) on Useful Role of Bacteria in Agriculture

Q.1. What is the useful role of bacteria?
Ans: Bacterias are useful to humankind in many ways. They are useful in agriculture, production of vitamins, medicines, and production of antibiotics, serums and vaccines, etc.

Q.2. Which bacteria is useful in agriculture?
Ans: Various kinds of bacteria, such as saprophytic, ammonifying, nitrifying, and nitrogen-fixing, are useful in agriculture.

Q.3. What is the economic importance of bacteria in agriculture?
Ans: The use of bacteria in agriculture can increase soil fertility, promote plant growth, reduce plant diseases, and increase crop production.

Q.4. What are the disadvantages of bacteria in agriculture?
Ans: Some bacterias can cause infections and produce toxins that are harmful to our health. Some bacteria can spoil food. Some bacteria may infect the plant and threaten the food supply.

Q.5. What is the role of fungi in agriculture?
Ans: Fungi produce various bioactive metabolites which can improve plant growth. Fungi supply inorganic nutrients to plants, such as ammonium, nitrate, and phosphate, and they can be used as biofertilizers.

We hope this article on the Useful Role of Bacteria in Agriculture helps you in your preparation. Do drop in your queries in the comments section if you get stuck and we will get back to you at the earliest.