Nutrient composition and chemical dynamics
- 20.5% Ammoniacal Nitrogen (NH4+): Nitrogen in the ammoniacal form binds securely to negatively charged soil clay particles, resisting rapid leaching losses compared to nitrate nitrogen.
- 24% Sulphate Sulphur (SO4²⁻): Supplies readily available sulphur for direct root uptake, without requiring microbial oxidation.
- Crystalline physical nature: White or off-white free-flowing crystals with low hygroscopicity, ensuring excellent storage stability and ease of mechanical broadcasting.
Rhizosphere acidification in alkaline soils
During nitrification, soil bacteria convert ammoniacal nitrogen into nitrate, releasing hydrogen ions into the root zone. This physiological acidifying effect temporarily lowers rhizosphere pH in neutral, alkaline, and calcareous soils, unlocking previously fixed phosphorus, iron, zinc, and manganese for active crop absorption.
Ideal crops and application practices
- Oilseeds (mustard, groundnut, soybean): Crucial for elevating seed oil synthesis and protein content.
- Alliums (onion, garlic): Essential for the formation of pungent allyl propyl disulphide volatile aromatic oils.
- Plantations and cereals: Widely applied in tea plantations, sugarcane, and paddy as a basal dressing or top-dressing.
- Incorporate into moist soil or irrigate immediately after surface application to prevent gaseous ammonia volatilization on alkaline ground.
Official source
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Department of Fertilizers (Govt of India) ↗Related on KisanPe
Common questions
What is the certified nutrient grade of ammonium sulphate fertilizer?
Under the Fertilizer Control Order (FCO), standard ammonium sulphate contains 20.5% ammoniacal nitrogen and 24% available sulphate sulphur.
Why is ammonium sulphate advantageous for mustard and onion farming?
Mustard requires high sulphur for synthesizing seed oil and glucosinolates, while onions require sulphur for bulb pungency and storage firmness.
Should ammonium sulphate be applied in highly acidic soils?
It should be used with caution in strongly acidic soils (pH below 5.5) as its acidifying reaction can further depress soil pH unless balanced with agricultural lime.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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