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UPPCS Chemistry Gap Sheet: Fertilisers and Plant Nutrients.
UPPCS has asked 17 of these. 3 have not been asked yet. Lock the first list, then read the second: it holds what UPPCS has not used yet.
First, the concept
Plants need several elements, not only nitrogen. Fertiliser grades normally report N directly, phosphorus as P₂O₅ equivalent and potassium as K₂O equivalent. These labels do not mean the bag contains free P₂O₅ or K₂O.
Nitrogen helps vegetative growth, phosphorus supports energy transfer and root development, and potassium helps water balance. Soil need, chemical form and nutrient availability matter more than simply adding more fertiliser.
✅ Already asked (17)
Common fertilisers
- Urea · CO(NH₂)₂; about 46% nitrogen, initially in amide form.
- DAP · Diammonium phosphate, (NH₄)₂HPO₄; standard grade 18–46–0.
- Ammonium sulphate · (NH₄)₂SO₄; about 21% N and 24% sulphur.
- Ammonium nitrate · NH₄NO₃; nitrogen in both ammonium and nitrate forms.
- Single superphosphate · Contains monocalcium phosphate and gypsum; supplies P, Ca and S.
- Muriate of potash · Potassium chloride, KCl; common potassium fertiliser.
- Sulphate of potash · Potassium sulphate, K₂SO₄; supplies potassium without chloride.
- Potassium nitrate · KNO₃; supplies nitrogen and potassium.
Nutrients and soil
- Sulphur and oilseeds · Sulphur supports oilseed crop quality; relevant to mustard oil content.
- Magnesium in chlorophyll · Magnesium is the central metal in chlorophyll.
- Iron chlorosis · Iron deficiency can cause yellowing of young leaves.
- Micronutrients · Examples include iron, zinc, boron, manganese, copper and molybdenum.
- Gypsum for sodic soil · Calcium from gypsum helps replace excess exchangeable sodium.
- Lime for acidic soil · Liming materials reduce soil acidity.
Biological nutrient supply
- Rhizobium · Fixes nitrogen in symbiosis with legume root nodules.
- Azotobacter · Free-living nitrogen-fixing bacteria used in biofertilisers.
- Azolla–cyanobacteria association · Used as a nitrogen-supplying biofertiliser in paddy systems.
❌ Not asked yet (3)
Items marked 'asked in other exams' have come in UPSC or other state exams, not yet in UPPCS.
🔒 3 items not asked yet
Common fertilisers: 2 · Nutrients and soil: 1
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⚠️ DAP 18–46–0 means 18% N and 46% P₂O₅ equivalent, not 46% elemental phosphorus.
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