A Fertilizer can be defined as a chemical substance manufactured to make the soil more fertile. It contains one or more valuable plant nutrients. It can be made available in different forms as per various commercial requirements.
Chemical fertilizers play an important role in crop production as the nutrient elements in fertilizer are present in higher concentration and in forms which can be readily utilized by plants directly or after rapid transformation. Their dose can be adjusted to suit the requirement as determined by soil fertility evaluation.
Fertilisers are grouped based on the nutrient present in the fertilizers namely nitrogenous fertilizers, phosphatic fertilizers, potassic fertilizers, boron fertilizer etc. Fertilizers are basically classified into 3 different types:
Straight Fertilisers are those which supply only one primary plant nutrient, namely nitrogen or phosphorus or potassium.
Examples: Urea, Ammonium sulphate, Potassium chloride, Potassium sulphate
Complex Fertilizers contains two or three primary plant nutrients of which two primary nutrients are in chemical combination. These fertilizers are usually produced in granular form.
Examples: Diammonium phosphate (DAP), Nitro phosphates, Ammonium phosphate
Mixed Fertilizers are physical mixtures of straight fertilizers. They contain two or three primary plant nutrients. Mixed fertilizers are made by mixing thoroughly the ingredients either mechanically or manually.
Based on concentration of primary plant nutrient (N P K), fertilizers are further classified into low and high analysis fertilizers.
The total content of primary nutrients is less than 25 % in low analysis fertilizers.
Examples: Single superphosphate (16 % P2O5), Sodium nitrate (16 % N)
The total content of primary nutrients is above 25 % is high analysis fertilizers.