Fertilizer Grades and Nutrient Composition
Zinc is an essential micronutrient required for plant auxin (IAA) synthesis, enzyme activation, and chlorophyll formation. Soils across major agricultural plains are chronically zinc-deficient due to intensive cropping.
Understanding the chemical grade ensures accurate dosage calculation under the Fertilizer Control Order.
- Zinc Sulphate Heptahydrate (ZnSO4.7H2O): Contains 21% elemental Zinc (Zn) and 10% Sulphur (S) in crystalline form.
- Zinc Sulphate Monohydrate (ZnSO4.H2O): Contains 33% elemental Zinc (Zn) and 15% Sulphur (S) in concentrated granular form.
- Khaira disease control: Basal application in rice paddies completely prevents Khaira disease (chlorotic bronzing of young rice leaves).
- Official price regulation: Subsidized under NBS guidelines; verified maximum retail prices are printed on certified packaging.
Application Protocols and Soil Health Integration
Zinc sulphate should be applied based on Soil Health Card recommendations during final land preparation.
Never mix zinc sulphate directly with phosphatic fertilizers (such as DAP or SSP) in the same slurry to avoid chemical precipitation.
- Soil application: Broadcast 10 to 25 kg per acre during basal land preparation depending on deficiency severity.
- Foliar spray: In standing crops showing deficiency, spray a 0.5% solution of zinc sulphate heptahydrate neutralized with 0.25% slaked lime.
- Separate phosphate application: Apply zinc and phosphatic fertilizers at different times or in separate soil bands to prevent insoluble zinc phosphate formation.
Official source
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Department of Fertilizers ↗Related on KisanPe
Common questions
What is the difference between 21% and 33% zinc sulphate?
The 21% grade is heptahydrate containing 21% Zinc, while the 33% grade is monohydrate containing 33% Zinc, requiring lower application volume.
Why should zinc sulphate never be mixed with DAP in the spray tank?
Mixing zinc with phosphate forms insoluble zinc phosphate precipitates that plants cannot absorb and that clog spray nozzles.
What crop symptoms indicate urgent zinc deficiency?
Symptoms include bronzing or rusty brown spots on young leaves (Khaira in paddy), white bud in maize, and stunted internodal rosetting.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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