Zinc sulphate grades and specifications
- Zinc Sulphate Heptahydrate (ZnSO4·7H2O): Contains a minimum of 21% elemental Zinc (Zn) and 10% Sulphur (S) in crystalline form.
- Zinc Sulphate Monohydrate (ZnSO4·H2O): Highly concentrated grade containing a minimum of 33% elemental Zinc (Zn) and 15% Sulphur (S) in powder or granular form.
- Both grades are regulated under Schedule I of the Fertilizer Control Order (FCO) with strict standards for chemical purity.
Deficiency symptoms and responsive crops
- Paddy: Corrects 'Khaira' disease, characterized by chlorotic patches on young leaves that turn rusty brown, leading to stunted tillering.
- Maize: Prevents 'White Bud' disease, where newly emerging leaves become bleached or pale white due to impaired auxin synthesis.
- Wheat, cotton, and citrus: Restores internode length, prevents 'little leaf' disorder, and enhances grain and boll development.
Application methods and precautions
- Soil application: Broadcast as a basal dressing during final land preparation, mixing thoroughly into topsoil.
- Do not mix zinc sulphate directly with phosphatic fertilizers (such as DAP or SSP) to avoid forming insoluble zinc phosphate.
- Foliar spray: In standing crops with acute deficiency, spray zinc sulphate neutralized with unslaked lime to avoid leaf burning.
Official source
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Department of Agriculture and Farmers Welfare ↗Related on KisanPe
Common questions
What is the difference between 21% and 33% zinc sulphate?
21% is zinc sulphate heptahydrate, while 33% is the more concentrated monohydrate formulation.
What is Khaira disease in paddy?
Khaira disease is a severe zinc deficiency in rice causing rusty bronze spots and stunted plant growth.
Why should zinc sulphate not be mixed directly with DAP?
Mixing zinc with phosphate forms insoluble zinc phosphate, making both nutrients unavailable to plants.
How is zinc deficiency identified in maize?
It causes 'white bud' disorder, where newly emerging terminal leaves turn bleached white or pale yellow.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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