Examples:

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Nitrogenous fertilizers (urea, ammonium sulfate);

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phosphate fertilizers (single/triple super phosphate);

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potassic fertilizers (muriate of potash); and

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macronutrients (Ca, Mg, O, C) and micronutrients (Zn, Mn, Cu, Fe, Mo, S, etc.).

Classification of fertilizers (see Fig. 4.3)

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Figure 4.3. Classification of fertilizers composition-wise.

1.

Straight fertilizers: Straight fertilizers only supply one primary plant nutrient, namely nitrogen or phosphorus or potassium. For example: urea, ammonium sulfate, potassium sulfate, and potassium chloride.

2.

Complex fertilizers: Complex fertilizers contain two to three primary plant nutrients of which two primary nutrients are in chemical combination. These fertilizers are usually produced in granular form. For example: DAP, nitrophosphate, and ammonium phosphate.

3.

Mixed fertilizers: These are physical mixtures of straight fertilizers. They contain more than two primary plant nutrients. These are prepared through systematic manual mixing of ingredients.

Fertilizers can also be classified based on physical form: (see Fig. 4.4)

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Figure 4.4. Classification of fertilizers based on physical form.

1.

Solid fertilizers are found in several forms:

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Crystals (ammonium sulfate);

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powder (single superphosphate);

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prills (urea, diammonium phosphate, superphosphate);

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briquettes (urea briquettes);

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granules (Holland granules); or

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supergranules (urea supergranules).

 

2.

Liquid fertilizers:

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Liquid form fertilizers are applied with irrigation water or through direct application.

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Their ease of handling, low labor requirement, and the possibility of mixing with herbicides have made liquid fertilizers more acceptable to farmers.