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:

• Ammonia
• Manure (Animal waste) which was the first fertilizer.
• Compost
• Urea

The important things in fertilizer are:

• Nitrogen (N)
• Phosphorus (P)
• Potash (K)

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.