Composition:

Viable Cell Count: CFU 1 X 10⁸ per ml min.

Contamination level: No Contamination at 10⁵ dilutions

pH: 5.0 to 7.5

1. Importance of Zinc in Agriculture

Zinc is an essential micronutrient for both plants and humans. In plants, it is vital for enzyme activation, chlorophyll synthesis, carbohydrate metabolism, and protein production. Zinc deficiency in crops leads to reduced growth, lower yields, and impaired nutritional quality.

2.  Mechanisms of Zinc Solubilization by Bacteria

ZSB employ several strategies to solubilize zinc in the soil:

• Organic Acid Production: ZSB secrete organic acids (e.g., gluconic acid, 2-ketogluconic acid), which lower the soil pH and solubilize insoluble zinc compounds like zinc oxide (ZnO) and zinc phosphate (Zn₃(PO4)₂).
• Siderophore Secretion: These metal-chelating molecules bind to zinc and other micronutrients, enhancing their availability for plant uptake.
• Oxido-Reductive Systems: Some ZSB use enzymatic processes to alter the oxidation state of zinc, making it more soluble.
• Phytohormone Production: ZSB can produce plant growth-promoting hormones like indole-3-acetic acid (IAA), which indirectly enhance zinc uptake by stimulating root growth.

3. Key Genera of Zinc-Solubilizing Bacteria

Several bacterial genera have been identified for their zinc-solubilizing capabilities:

• Bacillus and Pseudomonas: These are the most prevalent and effective ZSB, known for their ability to solubilize zinc and promote plant growth.
• Gluconacetobacter, Acinetobacter, Burkholderia, and Enterobacter: These genera also exhibit significant zinc-solubilizing potential.
• Rhizobacteria: Many ZSB are plant growth-promoting rhizobacteria (PGPR), which colonize plant roots and enhance nutrient uptake.

4. Applications in Agriculture

ZSB are widely used in sustainable agriculture for:

• Biofortification: Enhancing zinc content in edible parts of crops like grains, fruits, and vegetables to combat Zn malnutrition in humans.
• Soil Fertility Improvement: ZSB restore soil health by increasing the availability of zinc and other nutrients.
• Stress Alleviation: ZSB help plants tolerate abiotic stresses like drought and salinity by improving nutrient uptake and producing stress-alleviating compounds.
• Reduced Chemical Fertilizer Dependency: ZSB offer an eco-friendly alternative to synthetic zinc fertilizers, reducing environmental pollution and soil degradation.

5. Benefits of ZSB in Sustainable Agriculture

• Cost-Effectiveness: ZSB provide a low-cost solution for improving crop yields and nutritional quality.
• Environmental Sustainability: By reducing the need for chemical fertilizers, ZSB contribute to greener agricultural practices.
• Enhanced Crop Productivity: ZSB improve plant growth, yield, and resistance to diseases, making them valuable bioinoculants.

6. Recommendation:

• Irrigation:1 litre in one acre
• Seed Treatment: Seeds are coated with ZSB to promote early root colonization (10 ml per Kg seeds)
• Composting: ZSB are added to compost to improve phosphorus content