Biofertilizers are substances of biological origin. They contain microorganisms that enhance the fertility of the soil and increase the growth of plants. Biofertilizers include blue-green algae, bacteria and even mycorrhizal fungi. There are certain strains of microorganisms, including algae, fungi and bacteria, that make the main composition of the biofertilizers. They are classified into different groups based on their utilisation and work with the soil. Their main aim is to enrich the soil to provide better nutrition for the plants. This article will discuss the different types of biofertilizers available in the market as well as their importance and uses.
Classification of Biofertilizers
There are different types of biofertilizers, and they are usually classified based on the functions and nature of their biological origin.
Phosphate Biofertilizers
There are two phosphate biofertilizers: phosphorus solubilising biofertilizers and phosphorus mobilising biofertilizers.
- Phosphorus solubilising biofertilizers
In phosphorus solubilizing, biofertilizers solubilise the phosphate, taken from the inorganic and organic phosphate sources. The biofertilizers release phosphorus in the soil and fix the minerals within it. As a result, the soil pH reduces so that the phosphates can dissolve in it, and it secretes organic acids. Species of Penicillium, Pseudomonas, Aspergillus and even Bacillus are all examples of phosphorus solubilizing biofertilizers.
- Phosphorus mobilising biofertilizers
These biofertilizers are known for transferring phosphorus particles from soil to the cortex of the roots. Bacteria like AM Fungi, also known as arbuscular mycorrhiza, are phosphorus mobilising biofertilizers. The surface area of the roots is increased when the fungus penetrates the root cortex. The transfer of P ions increases due to the displacement in the absorption equilibrium of the phosphate ions. Arbuscle cells are known to absorb the nutrients into the roots after stimulating the metabolic process.
Biofertilizers for Micronutrients
Biofertilizers for micronutrients contain bacteria species that are mainly zinc and silicate solubilizers. The bacteria species are known to degrade aluminium silicates and silicates in the soil and, thus, help weather silicates. An example of a biofertilizer for a micronutrient is Bacillus sp.
Nitrogen (N2) Fixing Biofertilizers
There are three types of N2 fixing biofertilizers: free-living, symbiotic and associative symbiotic. Azotobacter, Anabaena, Clostridium and Nostoc fall under free-living nitrogen-fixing biofertilizers. While Anabaena Azollae, Rhizobium, and even Frankia come under symbiotic nitrogen-fixing biofertilizers. Last but not least, Associative symbiotic biofertilizers like Azospirillum are also nitrogen-fixing biofertilizers.
- Rhizobium Biofertillizers
Rhizobium is an example of symbiotic nitrogen-fixing biofertilizers infecting the legume plant roots. They continue the fixation process by creating root nodules to convert nitrogen molecules into ammonia. As a result, the plants utilise ammonia and produce vitamins, proteins and other compounds which contain nitrogen. The symbiosis of plants takes place in the root nodules.
Plant-growth Promoting Rhizobacteria (PGPRs)
Known as plant growth-promoting rhizobacteria, these bacteria species are biopesticides and biofertilizers. They promote growth in plants by improving the availability of nutrients, suppressing the different diseases that plants get diagnosed with and by producing plenty of phytohormones production. PGPRs include Bacillus sp and Pseudomonas sp.
Liquid Biofertilizers
Liquid biofertilizers fix the nitrogen in the atmosphere and solubilize the insoluble phosphates. After the process, they make it available for the plants. This reduces the utilisation of chemical fertilisers by a significant percentage and increases the shelf life. The plants also become tolerant to higher temperatures and free of contamination. Further, it becomes easier for the plants to reproduce and produce organic crops, thus, contributing to a greener world.
Composting Biofertilizers
The Biofertilizers specialise in composting animal dung to enrich the soil with microbes. It is one of the most eco-friendly organic fertilisers as it consists of nitrogen, various decomposing fungi and phosphate solubilizing bacteria. Microorganisms like Azotobacter and Cellulolytic fungi break down the organic material. Cow dung is one of the classic forms of biofertilizers that farmers have used across the world for centuries. They provide natural fertilisation to the soil, enriching it with nutrients for better plant growth.
Conclusion
Biofertilizers are microorganisms applied to increase the quality of the interior of plant roots while colonising the rhizosphere. As a result, they promote plant growth, free them from contamination and become the primary nutrition for the plant. Several types of biofertilizers are used in the agriculture and plant industry. They include nitrogen-fixing biofertilizers, phosphorus biofertilizers, biofertilizers for micronutrients, plant growth-promoting rhizobacteria, compost, and liquid biofertilizers.