🐛 Introduction to Biofertilizers

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Introduction to Biofertilizers

Biofertilizers are preparations containing living or latent cells of efficient strains of microorganisms that, when applied to seed, soil, or plant surfaces, colonize the rhizosphere or plant interior and promote growth by increasing the availability of nutrients to the host plant.

Definition

The Bureau of Indian Standards (BIS) defines biofertilizers as products containing carrier-based (solid or liquid) living microorganisms which are agriculturally useful in terms of nitrogen fixation, phosphorus solubilization, or nutrient mobilization, to increase the productivity of soil and/or crop.

Classification of Biofertilizers

Category	Microorganisms	Function
Nitrogen fixers	Rhizobium, Azotobacter, Azospirillum, BGA, Azolla	Fix atmospheric N2 into plant-available NH4+
Phosphorus solubilizers	Bacillus megaterium, Pseudomonas striata	Convert insoluble P into soluble H2PO4-
Phosphorus mobilizers	AM/VAM fungi (Glomus, Gigaspora)	Extend root absorption zone for P uptake
Potassium solubilizers	Frateuria aurantia, Bacillus mucilaginosus	Release K from silicate minerals
Plant growth promoters	Pseudomonas fluorescens, Bacillus subtilis	Produce hormones (IAA, GA), siderophores
Zinc solubilizers	Bacillus spp., Gluconacetobacter	Solubilize ZnO/ZnCO3 into available Zn2+

Importance in Sustainable Agriculture

• Supplement chemical fertilizers — biofertilizers can replace 20-25% of nitrogen and 15-25% of phosphorus from chemical sources
• Improve soil health — enhance organic matter, soil structure, and microbial diversity
• Cost-effective — significantly cheaper than chemical fertilizers, benefiting small and marginal farmers
• Eco-friendly — no pollution of soil and groundwater, no contribution to eutrophication
• Enhance nutrient use efficiency — solubilize fixed nutrients and improve fertilizer uptake
• Produce growth-promoting substances — phytohormones (IAA, gibberellins, cytokinins), vitamins, and siderophores

Government Support in India

The Indian government actively promotes biofertilizer usage through several schemes:

• National Project on Organic Farming (NPOF) — supports biofertilizer production centres
• Paramparagat Krishi Vikas Yojana (PKVY) — cluster-based organic farming with biofertilizer component
• Soil Health Card Scheme — recommends biofertilizer usage based on soil testing
• Capital subsidy of up to Rs. 190 lakh for establishing biofertilizer production units under NPOF

India's biofertilizer production capacity has grown from about 60,000 MT in 2014-15 to over 1,20,000 MT, with the government targeting further expansion to reduce dependence on imported chemical fertilizers and promote soil sustainability.

Limitations

• Shorter shelf life (typically 6-12 months) compared to chemical fertilizers
• Sensitivity to high temperatures, UV radiation, and desiccation
• Contamination risk during production and storage
• Inconsistent field performance due to soil, climate, and agronomic variability
• Farmer awareness and availability remain challenges in remote areas

Despite limitations, biofertilizers are indispensable for integrated nutrient management (INM) and the transition towards sustainable and organic agriculture.

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Introduction to Biofertilizers — definition, types, classification, and importance in sustainable agriculture.
Section context	Revise this lesson with the rest of Biopesticides and Biofertilizers for stronger conceptual continuity.