🧪 Classification of Fertilizers
Major fertilizer classes based on nutrient content, nutrient form, and agronomic use.
This lesson covers fertilizer classification systems and compares key nitrogenous fertilizers based on composition and nutrient form.
Classification basis
Commercial N, both organic and inorganic is desired from a wide variety of
materials which are found to differ very widely in their sources, properties, method of
preparation and their reactions in the soil. Classification based on chemical form seems
to be more satisfactory as indicated below.
The nitrogen content of different nitrogenous fertilizers is given below
| Sl.No | Name of the fertilizer |
N content (%) |
Form of N |
|---|---|---|---|
| 1 | Sodium nitrate (NaNO3) |
16.0 | Nitrate (NO3) |
| 2 | Potassium nitrate (KNO3) |
12.5-13.5 | Nitrate |
| 3. | Ammonium sulphate (NH4)2 SO4 |
20.6 | NH4 (Ammonia) |
| 4. | Ammonium chloride (NH4 Cl) |
26.0 | NH4 |
| 5. | Ammophos - A | 11.0 | NH4 |
| 6. | Ammophos – B | 16.0 | NH4 |
| 7. | Ammonium Nitrate (NH4) | 33.0 | NH4 – 16.5 NO3 – 16.5 |
| 8. | Ammonium sulphate nitrate | 25.6 | NH4 – 19.5 NO3 – 6.6 |
| 9. | Urea (CO (NH2)2) | 46.0 | Amide |
| 10. | Calcium cyan amide (CaCN2) |
20.6 | Amide |
| 11. | Dried blood | 3-14 | Protein(organic) |
| 12. | Groundnut cake | 8.0 | Protein(organic) |
| 13. | Meat meal | 09.0-11. | Protein (organic) |
| 14. | Guano | 10.0 | Protein (organic) |
Summary Cheat Sheet
| Topic | Key exam point |
|---|---|
| Basic classification | Straight, complex, and mixed fertilizers |
| Straight fertilizer | Supplies mainly one primary plant nutrient |
| Complex fertilizer | Contains two or more nutrients formed by chemical reaction |
| Mixed fertilizer | Blend of two or more fertilizers made by physical mixing |
| Nutrient-based classification | Nitrogenous, phosphatic, and potassic fertilizers |
| Secondary/micronutrient angle | Fertilizers may also be grouped by secondary nutrients and micronutrients |
| Source basis | Organic, inorganic/mineral, and biofertilizer-related categories are treated separately |
| Use basis | Basal, top-dressing, foliar, and special-purpose categories may appear in exams |
| Core distinction | Complex fertilizers are manufactured chemically; mixed fertilizers are physical blends |
| Trap | Do not write DAP/NPK complex under mixed fertilizers unless the question explicitly asks by commercial practice rather than manufacturing basis |
References
3 sources • [1] [2] [3]
References
[2]
Principles of Soil Science and Agricultural Chemistry — Standard BSc Agriculture Textbook
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