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Overview of Fertilisers
- Chemical Fertilisers: Supply essential nutrients to plants more efficiently than organic manure in terms of quantity and speed.
- Organic Manures: Less efficient at supplying concentrated nutrients. For example, one metric ton supplies only 2-3 kg of phosphorus.
Classification of Chemical Fertilisers (by Nutrient Content)
| Type | Primary Nutrient(s) | Examples |
|---|---|---|
| Nitrogenous | Nitrogen (N) | Urea, Ammonium Sulphate, Ammonium Nitrate, Calcium Ammonium Nitrate (CAN) |
| Phosphatic | Phosphorus (P) | DAP (Diammonium Phosphate) |
| Potassic | Potassium (K) | Various Potassium Salts |
| Mixed/Complex | Combination of N, P, K | NPK fertilizers |
Detailed Look at Specific Fertilisers
Urea
- Type: Nitrogenous fertiliser.
- Composition: An organic compound containing Carbon (C), Hydrogen (H), Nitrogen (N), and Oxygen (O).
- Nitrogen Content: Approximately 46-47% by weight.
- To supply 1 kg of nitrogen, about 2.2 kg of urea is required.
- Nitrogen Form: Supplies nitrogen in the amide form.
- Properties:
- Highly soluble in water.
- Most popular fertiliser for foliar application (sprayed on leaves).
- Neem-Coated Urea:
- Coating slows down the dissolution rate.
- Benefits: Improves Nitrogen Use Efficiency (NUE) and reduces environmental losses.
Other Specific Fertilisers
- DAP (Diammonium Phosphate): A complex fertilizer containing 18% Nitrogen and 46% Phosphorus (as P₂O₅).
- Ammonium Sulphate: Known for leaving the maximum acidity in the soil after application.
Plant Nutrients and Their Roles
| Nutrient | Primary Role / Function | Key Fact |
|---|---|---|
| Nitrogen (N) | Essential for growth and development. | Wheat cultivation requires nitrogenous fertilizers. |
| Phosphorus (P) | Crucial for root development. | – |
| Potassium (K) | Regulates stomatal opening and closing. | – |
| Boron (Micronutrient) | Involved in cell wall formation and reproductive development. | Its role is not primarily disease resistance. |
Plant Uptake of Nitrogen: Plants absorb nitrogen primarily as Nitrate (NO₃⁻) and sometimes as Ammonia (NH₃).
Soil Chemistry and Environmental Impact
- Soil Acidity: Excessive use of nitrogenous fertilisers can increase soil acidity. Ammonium Sulphate is notable for leaving maximum acidity.
- Environmental Concerns:
- Leaching: Inappropriate use can lead to nitrate leaching into groundwater, causing pollution.
- Nitrous Oxide: The use of neem-coated urea reduces the release of nitrous oxide, but does not eliminate it entirely.
Fertiliser Industry and Policy
- Production Inputs:
- Ammonia (for urea) is made from natural gas.
- Sulphur (for phosphoric acid) is a by-product of oil refineries.
- Carbon dioxide is consumed in the manufacture of urea.
- Government Policy (India): The retail price of chemical fertilizers is subsidized and administered by the Government, not market-driven.
Organic Manures and Green Manuring
- Green Manuring: The process of ploughing green plants into the soil to enrich it.
- Suitable Crop: Sunhemp is a very suitable crop for green manuring.
Non-Fertilizers
- Sodium Sulphate is not a chemical fertilizer.
- Humus is an example of an organic colloid and is part of organic manure, not a chemical fertilizer.
Know More About The Fertilizers: