What is fertiliser

Nitrogen (N) makes up about 78 percent of the air we breathe. It is inert and insoluble in this form.

To manufacture nitrogen fertiliser, it must be removed from the air and combined with hydrogen to make ammonia, which is then converted to urea. This is applied directly to crops as a nitrogen fertiliser or used as a building block to make other nitrogen fertiliser products.

Phosphorus (P) is present in all living cells and is essential to all forms of life. Found throughout our bodies, it is concentrated in our teeth and bones. The source of phosphorus in fertiliser is phosphate rock, which is typically mined from the earth's crust then reacted with acid to produce different phosphate products.

Potassium (K) is also found throughout nature and is found in our bodies in muscles, skin and the digestive tract. Good health requires sufficient intake of potassium. Plants use potassium for functions like photosynthesis and protein formation. Potassium, or potash, is mined from naturally occurring ore bodies that were formed as seawater evaporated. The deposits are a mixture of crystals of potassium chloride and sodium chloride. Sodium chloride is also known as table salt. After it is mined, the potassium chloride is purified into a granular fertiliser.

Sulphur (S) is essential to produce amino acids, which are the building blocks of proteins found in all living things. Sulphur also helps give crops like onion, mustard and radish their characteristic flavour. While it can be found naturally in the soil, it is not always in a form plants can use.