A fertilizer is a chemical that helps plants to grow. It is used to replace the mineral salts taken by plants or removed/washed away by rain.
Common fertilizers:
The important things in fertilizer are:
When fertilizers are offered for sale, the percentage of N, P, and K must be written on the bags or boxes, but for historcal reasons, P is shown as %P2O5 and K is shown as %K2O.
E.g.:9-23-30 which means: 9% N, 23%P2O5 and 30%K2O.