Fertilizers are chemical substances supplied to the crops to increase their productivity. The fertilizers contain the essential nutrients required by the plants including nitrogen, potassium, and phosphorus. They enhance the water retention capacity of the soil and also increase its fertility.

Fertilizers are divided into the following four groups:

(i) Nitrogenous fertilizers: These fertilizers supply the macronutrient nitrogen.

Example: Urea, CO(NH₂)₂

(ii) Potassic fertilizers: These fertilizers supply potassium which is one of the essential macronutrients of the plants.

Example: Potassium sulphate, K₂SO₄.

(iii) Complex fertilizers: These fertilizers contain two or more nutrients.

Example: Nitrophosphate