Nutrient Composition & Technical Specifications
NPK 00:00:50 is governed by strict statutory specifications under Schedule I of the Fertilizer Control Order (FCO), 1985. It provides potassium in the sulfate form, ensuring balanced nutrition without introducing harmful chloride ions.
Unlike Muriate of Potash (MOP / Potassium Chloride), SOP features an exceptionally low salt index (46 compared to 116 for MOP), minimizing osmotic root stress in intensive greenhouse and drip fertigation systems.
- Water-Soluble Potash (K2O): 50% w/w minimum in fully dissolved, plant-absorbable form
- Total Sulphur (S): 17.5% w/w minimum in available sulfate (SO4) form
- Chloride Content: Maximum 2.0% (practically chlorine-free under FCO standards)
- Moisture & Solubility: Maximum 1.5% moisture; 100% water soluble without gritty sediment
Physiological Benefits for Fruit Quality & Yield
Potassium is the primary osmotic regulator in plant cells, activating over 60 enzymes responsible for carbohydrate transport, protein synthesis, and stomatal opening. Sulphur is an essential component of amino acids (methionine, cysteine) and aromatic glucosinolates.
Applying 00:00:50 during fruit development dramatically increases fruit diameter, enhances coloration, increases Total Soluble Solids (Brix sugar content), and extends post-harvest shelf life.
- Sugar Accumulation: Accelerates starch-to-sugar translocation into fruits, grapes, and sugarcane
- Crop Quality: Enhances rind firmness, aroma, and natural color in pomegranates, apples, and tomatoes
- Abiotic Stress Tolerance: Regulates cell turgor to protect crops against heat waves, drought, and frost
- Chloride-Sensitive Crops: Indispensable for tobacco, potato, grape, strawberry, citrus, and onion cultivation
Application Timing & Fertigation Compatibility
SOP 00:00:50 is applied primarily during the reproductive, fruit filling, and pre-harvest ripening stages via drip irrigation or foliar spraying.
When preparing stock solutions for fertigation, SOP is compatible with urea, ammonium sulfate, and phosphoric acid, but should not be mixed with concentrated calcium nitrate to avoid forming insoluble calcium sulfate precipitates.
- Fruit Filling Stage: Apply through drip irrigation during rapid fruit or tuber sizing
- Foliar Feeding: Spray during late afternoon hours at standard manufacturer recommended dilution rates
- Stock Tank Precaution: Do not mix with Calcium Nitrate in Tank A; dissolve in Tank B (potash/acid tank)
Official source
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Department of Fertilizers, Government of India ↗Related on KisanPe
Common questions
What is the key difference between MOP (00:00:60) and SOP (00:00:50)?
MOP contains chloride (Potassium Chloride), which can burn chloride-sensitive crops like potatoes, grapes, and tobacco; SOP is chlorine-free and contains 17.5% essential sulphur.
At what crop stage should 00:00:50 be applied?
It should be applied during the fruit development, bulb enlargement, grain filling, and pre-harvest ripening stages to enhance size, sweetness, and market appeal.
Is 00:00:50 safe for foliar spray on standing crops?
Yes, its low salt index and high solubility make it very safe for foliar application when dissolved at standard recommended concentrations during cool hours.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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