Biofertilizer
- Biofertilizers are the substances of biological origin (microorganisms), which when added to the soil enhances its fertility and promotes plant growth.
- Broadly, biofertilizer constitutes of living organisms which include mycorrhizal fungi, blue-green algae, and bacteria. Biofertilizers simply consists of specific strains of microorganisms like bacteria, fungi, algae or their combinations.
- Mycorrhizal fungi uptakes minerals from organic matter for the plant whereas cyanobacteria are characterized by the property of nitrogen fixation. The process of conversion of the atmospheric Nitrogen into nitrogenous compounds in soil ready for plant to absorb in series of reaction is termed as nitrogen fixation.
- And the bacteria can be nitrogen fixers or phosphate solubilizers. They convert insoluble forms of soil phosphorus into soluble forms. As a result, phosphorus will be available for plants
- Biofertilizers are economical, effective, and renewable sources of plant nutrients.
- The role of biofertilizers in agriculture production shows a special importance, particularly in the present context of the sky-rocketing cost of agriculture inputs.
- The selective strains of microorganisms be used to prepare biofertilizer, for economic purpose and for significant results.
- When these prepared biofertilizers are incorporated with seeds, setts, seedlings or soil, they improve crop productivity and soil health, by the biological nitrogen fixation process, solubilisation and uptake of other nutrients and synthesis of growth-promoting substances such as vitamins and plant growth hormones.
- They also produces capsular polysaccharides to prevent soil erosion.
- They also convert immobilised chemical into soluble forms and make them accessible to the plants.
- Biofertilizers is highly advantageous over chemical fertilisers.
Advantages of biofertilizers:
- The biofertilizers has special contribution to agriculture due to the following advantages:
- Biofertilizers act as supplements to chemical fertilisers.
- Biofertilizers are cost-friendly and can aid to decrease consumption of such fertilisers.
- Microbes in biofertilizers provide atmospheric nitrogen directly to plants.
- They aid in solubilisation and mineralisation of other plant nutrients like phosphates.
- Better synthesis and availability of hormones, vitamins, auxins and other growth-promoting substances improves plant growth.
- On an average crop yield elevates by 10–20 percent by their use.
- They help in the multiplication and survival of beneficial micro-organisms in the root region (rhizospheric bacteria).
- They control and inhibit pathogenic soil bacteria.
- They enhance soil texture by increasing amount of humus and maintain soil fertility.
- Eco-friendly in nature and pollution free.
Types of biofertilizers:
- Biofertilizers are broadly classified into two main groups:
- Biological nitrogen fixing biofertilizers
- Phosphate solubilising (mobilising) biofertilizers
- Biological nitrogen fixing biofertilizers consist of micro-organisms which have the ability to fix biological molecular nitrogen (N2) either symbiotically or asymbiotically in the plants.
- Phosphate solubilising biofertilizers are capable of solubilising or mobilising the fixed insoluble phosphates of the soil
- However, Biofertilizers are divided into five main categories.
- These five types are again divided in sub-types as follows:
- i. Nitrogen fixers:
- Symbiotic: Rhizobium, Frankia, Anabaena azollae.
- Free living: Azotobacter, Clostridium, Blue green algae, Azolla, Acetobacter, Nostoc, Anabaena.
- Associative symbiotic: Azospirillum.
- ii. Phosphate supplier:
- Phosphate solubiliser:
Bacteria: Bacillus megaterium, Phosphaticum, Bacillus circulans, Pseudomonas striata, Pseudomonas sp.. - Fungi: Penicillium sp, Aspergillus awamori.
- Phosphate solubiliser:
- iii. Phosphate absorber biofertilisers:
- Arbuscular mycorrhiza: Glomus sp., Gigaspora sp., Acaulospora sp., Scutellospora sp. and Sclerocystis sp., Ectomycorrhiza: Laccaria sp., Pisolithus sp., Boletus sp., Amanita sp. Orchid mycorrhiza: Rhizoctonia solani.
- iv. Sulphur supplier:
- Thiobacillus novellus, Aspergillus.
- v. Micronutrients supplier:
- Silicate and Zinc solubilisers: Bacillus sp.
Application-Method of applying biofertilizers
- The important method of biofertilizers applications are listed below:
- Seedling root dip:
- This method is usually applicable for rice crops. The seedlings are sowed in the bed of water and kept for 8-10 hours.
- Seed Treatment:
- The seeds are soaked in the mixture of nitrogen and phosphorus fertilizers. These seeds are then left to dry and are sown as soon as possible.
- Soil Treatment:
- The biofertilizers along with the compost fertilizers are blended and kept for one night. This mixture is then scattered on the soil where the seeds have to be sown.
Disadvantages of biofertilizers
- Biofertilizers are supplement to chemical fertilizers but not substitute to it.
- Biofertilizers only result in 20 to 30 percent increase in crop production. They do not cause marked increase in productivity like chemical fertilizer.
- Specific fertilizers are required for specific crops. This is more applicable to symbiotic micro-organisms. If non-specific Rhizobium is used as fertiliser, then it will not lead to root nodulation and increase in crop production.
- During the production of microbial fertiliser, strict aseptic precaution is needed. Contamination is a common issue during microbial mass production.
- If exposed for long time in sunlight, microbes get killed as they are light-sensitive.
- Microbial fertilizer must be used within six months after production when stored at room temperature and within two years if stored at chilling temperature.
- Efficiency of microbial fertilizer depends on soil character, such as, moisture content, pH, temperature, organic matter and types of micro-organisms present. When these factors are unfavourable microbial fertilizer may not be effective in enhancing the soil fertility.