Standard NPK Water-Soluble Fertilizer Grades
Under Schedule I, Part A of the FCO, the Government of India has notified multiple 100% water-soluble complex grades. Each formulation is engineered for specific phenological stages of plant development.
Using the appropriate grade ensures balanced nutrient delivery without soil nutrient fixation, excessive leaching, or salinity accumulation in intensive cropping systems.
- NPK 19:19:19 / 20:20:20: Balanced general-purpose vegetative grade for early plant establishment
- NPK 12:61:00 (Mono Ammonium Phosphate / MAP): High-phosphorus root development and tillering grade
- NPK 13:40:13: High-phosphorus foliar grade for root vigor and floral bud differentiation
- NPK 00:52:34 (Mono Potassium Phosphate / MKP): Nitrogen-free bloom booster and disease-suppression grade
- NPK 13:00:45 (Potassium Nitrate): Clean nitrogen-potash source for rapid fruit sizing and color development
- NPK 00:00:50 (Potassium Sulphate / SOP): Chlorine-free potash with 17.5% sulphur for ripening and sugar accumulation
Secondary & Micronutrient Soluble Formulations
In addition to NPK complexes, specialized straight soluble salts deliver vital secondary nutrients (calcium, magnesium, sulfur) and micronutrients (zinc, iron, boron, copper, manganese).
Chelated formulations (e.g., Fe-EDTA, Zn-EDTA) prevent metal ions from precipitating in alkaline fertigation water, maintaining nutrient availability across a wide root-zone pH range.
- Calcium Nitrate (15.5% N, 18.8% Ca): Essential for cell wall elasticity, apical bud growth, and blossom end rot prevention
- Magnesium Sulphate (9.6% Mg, 12% S): Vital core element of chlorophyll molecules for photosynthetic efficiency
- Chelated Micronutrients (EDTA Zn, Fe, Cu, Mn): Chemically protected micronutrients for complete drip solubility
- Boron (Disodium Octaborate Tetrahydrate 20% B): High-solubility foliar boron for pollen tube germination and fruit set
Two-Tank Fertigation Compatibility Rules
To prevent chemical reactions that produce insoluble precipitates in drip lines, modern fertigation systems utilize a two-tank (Tank A and Tank B) stock solution strategy.
Calcium fertilizers must never be dissolved in the same concentrated tank as sulfate or phosphate fertilizers, as they form insoluble gypsum (calcium sulfate) or rock phosphate precipitates.
- Tank A (Calcium & Iron): Dissolve Calcium Nitrate, Potassium Nitrate, and Chelated Iron
- Tank B (Phosphates & Sulfates): Dissolve MAP (12:61:00), MKP (00:52:34), SOP (00:00:50), and Magnesium Sulphate
- Tank C (Acid/pH regulation): Dilute phosphoric acid or nitric acid to regulate irrigation water pH to 5.8-6.5
Official source
Check the latest rules, benefits and forms here. KisanPe is an independent platform and is not a government website.
Fertilizer Control Order (FCO), Department of Agriculture & Farmers Welfare ↗Related on KisanPe
Common questions
Why are water-soluble fertilizers more efficient than conventional granular fertilizers?
Water-soluble fertilizers dissolve completely in water and are delivered directly to the root zone via drip, resulting in 80% to 90% nutrient uptake efficiency compared to 30% to 50% for soil-broadcast granular fertilizers.
Which water-soluble fertilizer grade is best for flowering and fruit set?
NPK 00:52:34 (MKP) is ideal during pre-flowering and floral initiation because high phosphate stimulates flower buds while potassium strengthens cell structure without excessive vegetative nitrogen flushes.
What happens if Calcium Nitrate is mixed with 19:19:19 in a concentrated tank?
The soluble calcium reacts with the phosphate in 19:19:19, forming an insoluble white calcium phosphate precipitate that clogs drip emitters and filters.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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