Biofertilizers are nutrient supplements for the plants. They possess various kinds of microbes that enhance soil fertility.
Dr. Norman Borlaug introduced the green revolution to enhance food production. But this also resulted in the excess use of chemical fertilizers and pesticides.
This leads to alarming environmental concerns like nutrient imbalance, reduced soil microorganisms, an increase of pest and disease attacks, water and soil contamination, etc.
It triggered the need for an alternate supply of plant nutrients.
Thus, Integrated Nutrient Management came into existence, and biofertilizers took momentum due to their benefits.
Due to the prolonged use of chemical fertilizers, soil quality gets degraded. These chemicals cause a change in pH, soil organic matter reduction, and a decrease in microbial activity. This leads to a reduction in the yield.
Natural fertilizers combat this issue by multiplicating living microbes in the rhizosphere, enhancing the soil’s water-holding capacity, and providing essential plant growth promoting substances to the soil.
Types of biofertilizers
Biofertilizers are classified into different groups based on their nature.
- Nitrogen-fixing bacteria- Azotobacter, Rhodospirillum
- Nitrogen-fixing cyanobacteria ( blue-green algae)- Anabaena, Nostoc
- Loose Association of nitrogen-fixing bacteria- Azospirillum
- Symbiotic nitrogen-fixing bacteria-Rhizobium, Frankia
- Plant growth-stimulating fungi- Trichoderma, Arbuscular mycorrhizae
It is a free-living gram-negative bacteria that live in the root nodules of leguminous crops.
They show a symbiotic relationship by taking food from the plants and, in turn, providing nitrogen to them.
Rhizobium bacteria infect root nodules and reduce molecular nitrogen into ammonia; plants uptake the nitrogen in the form of ammonia.
This process is called biological nitrogen fixation. It is estimated that Rhizobium fixes 40-250 kg N/ha in a year.
This is a free-living nitrogen-fixing bacteria. They fix atmospheric nitrogen in cereal crops. It improves seed germination and plant growth. They also can produce antifungal compounds against many plant pathogens.
These are gram-negative motile bacteria. They have an association with the roots of monocots. These organisms increase the growth of sunflower cotton, sugar beat, carrot, etc. The increase in yield by azospirillum is estimated as 5-30%.
Plant Growth Promoting Rhizobacteria (PGPR)
Various bacteria that promote the growth of plants collectively are known as PGPR. These include bacillus, pseudomonas, Xanthomonas, streptomycin, etc. Bacillus act as a biocontrol agent.
Phosphorus solubilizing bacteria
Phosphorus is a vital nutrient after nitrogen, which is essential for plant development. This is important for promoting nodulation by Rhizobium and other nitrogen fixers. Phosphorus is made available to the plants by Phosphorus solubilizing bacteria. This is among the most used biofertilizer.
Arbuscular mycorrhiza (AM fungi)
An arbuscular mycorrhiza (AM Fungi) is a type of mycorrhiza fungus that penetrates the cortical cells of a vascular plant’s roots.
a. Collection of soil sample:
Collect the soil sample at a depth of 6-15 cm from the rhizosphere of rice, mango, brinjal, papaya, guava, etc.
b. Isolation of Microorganism from the soil sample
- Add 1 gm of each soil sample to 10 ml water and stir it thoroughly.
- Take each sample and streak them in 7 different plates with Jensen media.
- Incubate these plates at 30-degree celsius for three days
- After the growth, immediately go for sub-culturing
c. Production of Mother Culture:
The Pure growth of any organism on a small scale is called mother culture.
- Take 1-liter conical flask and add 500 ml broth media to it
- Plug non-absorbent cotton and sterilize it in the autoclave for 15-20 minutes at 15 lbs pressure for 15 minutes
- Inoculate mother culture into the flask
- transfer the flask to the Shaker and shake it for 72- 90 hours to get optimum growth of bacteria in the broth
- You can get the biofertilizer by this process. Pack them in plastic bags and store them in a cool place.
d. Selection of the carrier:
A carrier is a substance rich in organic matter, has a higher water holding capacity, and supports the organisms’ growth. For easy transport of biofertilizers, select a suitable carrier like lignite, compost, or peat soil.
- Take some charcoal and adjust the pH of the charcoal by adding CaCO3(1:10).
- Autoclave the carrier at 15 lbs pressure for 60 minutes.
- After this, the broth is added with the carrier (lignite) in a 1:3 ratio.
e. Mixing and packaging:
- Sterilize galvanize trace and transfer previously sterilized lignite
- then add broth ( 3:1- lignite: broth) and mix properly
- keep the trays one above the other for 10 to 12 hours; this will help the microorganisms to multiply in the carrier
- Fill this mixture in plastic bags and see them
- Live in the bags properly and store them in a cool place
Method of application of biofertilizers
- Take a proportion of seeds that are to be inoculated by the biofertilizer.
- Take any nitrogenous or phosphoric fertilizer and add some water to make a slurry.
- Apply the slurry uniformly on the seeds and dry them (to adhere biofertilizers to the seeds, you can use jaggery)
- Now, these seeds are ready to use for sowing.
Seedling root dip treatment :
This method of biofertilizer application is used when crops are grown through seedlings.
- Take some quantity of water and add biofertilizers to it and mix them properly
- now dip the seedlings in this mixture to enable the roots to get this inoculum
- these seedlings can now be used for transplanting
- Take 50 liters of water in a drum and add 4-5 kgs of biofertilizer to it. Mix them properly
- now take the tubers required to plant for 1 acre of land and dip them in this mixture
- These tubers are now ready to be planted.
This method is mostly used for sugarcane, fruit crops, and other trees.
- Take 25 kg of FYM and 2 kg of any biofertilizer.
- Mix them properly and keep them overnight.
- It is ready to be applied to the plants now.
Advantages of biofertilizers
- Harness nitrogen fixation and increase phosphorous uptake by soil.
- Increase crop yield by 10 to 15%.
- They enhance root proliferation by releasing growth-promoting hormones.
- Biofertilizers improve soil properties and retain soil fertility.
- They are cost-effective and environmentally friendly.
Disadvantages of biofertilizers
- Biofertilizers have a short shelf life.
- They show delayed results and require skilled labor.
- The soil must contain adequate nutrients for the organisms to show their effect.
- They are thermosensitive
- Excessive acidic or alkaline soils hamper their growth.
With the change in the lifestyle of people, food habits too have changed hugely. Awareness among the people has spread rapidly, and they became conscious of their health. People prefer organic foods over chemically grown foods, and this has revolutionized the food sector.
Being organic supplements of the plants, biofertilizers gained their popularity. These are used on a large scale due to their numerous benefits, like increasing the crop’s productivity by adding nutrients to the soil and improving water holding capacity. Though they have a short lifespan, they are cheaper and can be easily used by the farmers.