Fertilizers are any solid, liquid or gaseous substances containing one or more plant nutrients.
They are either applied to the soil, directly on the plant (foliage) or added to aqueous solutions, in order to maintain soil fertility, improve crop development, yield and/or crop quality.
The purpose of fertilizers are to supplement the natural supply of soil nutrient, build up soil fertility in order to satisfy the demand of crops with a high yield potential and to compensate for the nutrients taken by harvested products or lost by unavoidable leakages to the environment, in order to maintain good soil conditions for cropping.
Manufactured fertilizers are classified according to different criteria as follows:
Number of nutrients
Type of combination
- single-nutrient or straight fertilizers (whether for macro or micronutrients);
- multi-nutrient/compound (multiple nutrients) fertilizers, with 2, 3 or more nutrients.
- mixed fertilizers or ‘bulk-blends’ are physical mixtures of two or more single-nutrient or multi-nutrient fertilizers.
- solid (crystalline, powdered, prilled or granular) of various size ranges;
- liquid (solutions and suspensions);
- gaseous (liquid under pressure, e.g. ammonia).
- quick-acting (water-soluble and immediately available);
- slow-acting (transformation into soluble form required, e.g. direct application of phosphate rock);
- controlled-release by coating;
- stabilized by inhibitors.