PROPERTIES AND IDENTIFICATION OF FERTILIZERS

Characteristics Nitrogenous Fertilizers

1. Highly soluble in water.
2. Highly mobile in the soil hence it is applied as a top dress.
3. Easily leached because of the high solubility hence does not have residual effect on the soil.
4. Has scorching effect on young crops during wet seasons.
5. Easy to volatilize during hot season.
6. They have a tendency to cake under moist conditions.
7. They are hygroscopic hence should be stored in dry conditions.

Examples:

Sulphate of Ammonia (NH4) 2 SO4-

Physical appearance:

1. white crystals,
2. Has acidic effect,
3. Contains 20% N.

Ammonium Sulphate Nitrate [(NH4), SO4+ NH4 NO;]

Colour: granules which appear yellow orange,

1. Less acidic,
2. Contains 26% N.

Calcium Ammonium Nitrate (CAN)

Colour: greyish granules,

Neutral in nature, contains 21 % N.

Urea

Colour: small whitish granules

Easily leached or volatilized,

Contains 45- 46%N.

Phosphate Fertilizers

1. Has low solubility and immobile.
2. Non-scorching.
3. Has a high residual effect hence benefit the next season’s crop.
4. Easy to store because they are not hygroscopic.

Examples;

Single super-phosphate

1. Appearance: whitish, creamy white granules,
2. Contains 20-21 % P, O5

Double super-phosphate

Appearance: dark greyish granules,

Contains 40-42% P205

Triple super-phosphate

Appearance: small greyish granules,

Contain 44-48% P205

Potassic Fertilizers

Characteristics:

1. Has moderate scorching effect.
2. Moderately soluble in water.
3. Most Kenyan soils have sufficient potassium.

Examples;

Marinate of Potash (KCI)

1. Contain 60 – 62% K10
2. Slightly hygroscopic.
3. Appearance amorphous white.

Sulphate of Potash (50% K10)

Compound or Mixed Fertilizers

These are fertilizers which supply 2 or more of the macronutrients.

Examples;

1. Mono ammonium phosphate.
2. Di-ammonium phosphate
3. 20:20:20, 23:23:23

Advantages of application of compound fertilizers

1. Saves time and money.
2. Mixture gives improved storage properties and better handling.

Disadvantages of compound fertilizers application

1. Mixing may not be thorough.
2. Incompatibility of the individual fertilizers.