Fertilisers provide nutrients to the soil and enrich its quality. But, increased application of chemical fertilisers to crops to meet the rising food demand has hampered the soil health by affecting its chemical composition as well as soil biodiversity. Moreover, when it rains, the fertilisers wash away from the soil and pollute surface water and groundwater. They also enter the human body through drinking water and the food we consume, having a detrimental effect on our health.
In this light, biofertilizers are environmentally-friendly alternatives which do not have ill-effects on the environment and human health. They aid sustainable agricultural practices by improving the fertility and productivity of the soil.
Biofertilizers are preparations containing live or latent cells of beneficial microorganisms. They are applied to seeds or soil to make naturally abundant nutrients in soil and atmosphere, available to plants. Biofertilizers contain different types of beneficial organisms such as bacteria, algae and fungi. Every microorganism, and hence every kind of biofertilizer, has a specific capability and function.
Biofertilizers containing nitrogen-fixing microorganisms such as Azotobacter, Clostridium and Rhizobium convert atmospheric nitrogen into ammonia with the help of an enzyme called nitrogenase. They do so through a process called biological nitrogen fixation (BNF). Nitrogen is an essential component of chlorophyll, a compound required by plants for photosynthesis.
Another critical group of biofertilizers contain phosphate solubilising microbes such as Pseudomonas and Bacillus. They convert insoluble phosphorus into a soluble form that can be absorbed by plants. Phosphorus is an essential component of nucleic acid as well as proteins and is required by the plants for cell division and proper growth. Similarly, other prominent groups of biofertilizers enhance plant growth by producing various essential enzymes and hormones.
Although biofertilizers are cost-effective and eco-friendly alternatives to chemical fertilisers, they have specific limitations. They have a shorter shelf-life than chemical fertilisers, can be easily contaminated by unwanted microbes, and there is a lack of knowledge of its use among farmers. However, scientists are working on developing carrier materials that increase the effectiveness of biofertilizers, liquid formulations of biofertilizers with a longer shelf life, and optimising production methods to prevent contamination.