What are bio-fertilizers? Classify biofertilizers based on their types and application

Biofertilizers are natural fertilizers that contain living microorganisms which enhance the fertility of the soil by promoting the growth of plants.

These microorganisms help in the biological fixation of nutrients, decomposition of organic matter, and the enhancement of soil structure, making essential nutrients more available to plants.

Classification of Biofertilizers

Biofertilizers can be classified based on their types (the kind of microorganisms they contain) and their application methods. Here’s a detailed classification:

**1. *Based on Microorganisms*

1. Nitrogen-Fixing Biofertilizers

• Rhizobium: Symbiotic bacteria that fix atmospheric nitrogen in the root nodules of leguminous plants (e.g., beans, peas, lentils). They convert atmospheric nitrogen into a form that plants can use.
• Azotobacter: Free-living bacteria in the soil that fix atmospheric nitrogen independently of plant roots. They are effective for non-leguminous plants and can be applied directly to the soil.
• Azospirillum: Bacteria that live in association with the roots of a wide range of plants, fixing atmospheric nitrogen and promoting plant growth.

1. Phosphate-Solubilizing Biofertilizers

• Bacillus: Bacteria such as Bacillus megaterium and Bacillus subtilis that solubilize insoluble phosphate compounds in the soil, making phosphorus more available to plants.
• Penicillium: Fungi that help in solubilizing phosphate and making it available to plants.
• Mycorrhiza: Symbiotic fungi that form associations with plant roots, enhancing the uptake of phosphorus and other nutrients.

1. Potassium-Solubilizing Biofertilizers

• Bacillus mucilaginosus: Bacteria that help in solubilizing potassium from soil minerals and making it available to plants.
• Frateuria aurantia: Another bacterium that helps in potassium mobilization.

1. Organic Matter Decomposers

• Actinomycetes: Filamentous bacteria that decompose complex organic matter in the soil, contributing to soil fertility.
• Cellulolytic and Lignolytic Fungi: Fungi that break down cellulose and lignin in plant residues, enhancing the organic matter content of the soil.

1. Biopesticides

• Trichoderma: Fungi used to control soil-borne plant diseases and enhance plant growth by decomposing organic matter and promoting root development.
• Bacillus thuringiensis: Bacteria used to control specific pests, reducing the need for chemical pesticides.

2. Based on Application Methods

1. Seed Treatment Biofertilizers

• Description: Applied directly to seeds before planting to promote early plant growth and improve seedling establishment.
• Examples: Rhizobium inoculants for legumes, Azospirillum for cereals.

1. Soil Application Biofertilizers

• Description: Applied directly to the soil either before or after planting to enhance soil fertility and nutrient availability.
• Examples: Mycorrhizal fungi inoculants, phosphate-solubilizing bacteria like Bacillus.

1. Folioar Spray Biofertilizers

• Description: Applied to the leaves of plants in the form of a spray to provide nutrients directly to the plant and improve growth.
• Examples: Certain strains of Azotobacter and phosphate-solubilizing bacteria can be used in foliar sprays.

1. Compost and Manure Enrichment

• Description: Biofertilizers are added to compost or manure to enhance their nutrient content and beneficial microbial activity before application to the soil.
• Examples: Adding nitrogen-fixing bacteria or mycorrhizal fungi to compost.

1. In-Furrow Application

• Description: Applied directly to the planting furrows during planting to ensure close contact with the plant roots.
• Examples: Rhizobium inoculants for legumes, Azospirillum for cereals.

Summary

Biofertilizers are natural fertilizers that use living microorganisms to enhance soil fertility and plant growth. They are classified based on the types of microorganisms they contain, such as nitrogen-fixing, phosphate-solubilizing, potassium-solubilizing, and organic matter decomposers, as well as biopesticides. They can also be categorized based on their application methods, including seed treatment, soil application, foliar spray, compost enrichment, and in-furrow application. Each type and application method is tailored to specific plant needs and soil conditions, contributing to sustainable agricultural practices.