Fertilisers are plant nutrients .
Nutrients existing naturally in the soil, atmosphere, and in animal manure. However, naturally occurring nutrients are not always available in the forms that plants can use, or in the quantities needed. So we add to them by applying fertiliser, to make plants grow to their maximum potential.

Fertilisers can be classified into two categories: organic  or inorganic.

Organic fertilisers are derived from living or once-living material, including animal wastes, crop residues, compost and numerous other by-products of living organisms.

Inorganic fertilisers are derived from non-living sources and include most of our man-made, commercial fertilisers. Man-made and natural fertilisers contain the same elements, but man-made
fertilisers act more quickly .

Often, the soil doesn't hold enough of these nutrients in the quantities needed for desirable growth and production.

An element is considered essential if in its absence plant growth and reproduction is significantly hindered.

The nutrients, that are in the soil, are often used up and need to be replaced. Therefore, we need to add extra plant nutrients to obtain maximum plant performance.