2. Three secondary macro nutrients: calcium (Ca), sulphur (S), magnesium (Mg).
3. And trace minerals (micro nutrients): boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo) and selenium (Se).
Without nitrogen, green plants would be weak and smaller than they should be. Phosphorus is vital to the growth and health of plants. It assists in converting the sun's energy and other chemicals (nitrogen) into usable food for plants. A phosphorus deficiency will lead to stunted looking plants that produce a lower quality fruit or flower. Potassium, often called potash, helps plants use water and resist drought. It promotes healthy green plants. It is important to food crops and enhances the size of fruits and vegetables.
The macro nutrients are taken in, in larger quantities and are present in plant tissue in amounts from 0.2% to 4.0% . Micro nutrients are consumed in smaller quantities and are present in plant tissue in quantities measured in parts per million (ppm), ranging from 5 to 200 ppm.
The main way of labelling fertilisers is using an NPK analysis. This shows the quantity of nitrogen, potassium and phosphorous in the fertiliser.
For example. The fertiliser potash (potassium carbonate) is composed of 1:1 potassium to carbonate by volume 47:53.
So, 100g of potassium chloride (KCl) would yield 60g of potassium oxide (K2O). The percentage yield of K2O from the original 100g of fertilizer is the number shown on the label. A potash fertilizer would thus be labelled 0-0-60.
Inorganic fertilisers are often synthesized using the Haber process, which produces ammonia as the end product. This ammonia is used as a food for other nitrogen fertilizers, such as anhydrous ammonium nitrate and urea.
Ammonia nitrate is a common high nitrogen fertiliser. The acid-base reaction of ammonia with nitric acid gives a solution of ammonium nitrate. It is 34.5% nitrogen
HNO3(aq) + NH3(g) → NH4NO3(aq)
ammonia + nitric acid→ ammonium nitrate.
Organic fertilisers are fertiliser compounds that contain one or more kinds of organic matter. The ingredients may be animal or vegetable matter or a combination of the two.
Processed organic fertilisers include compost, blood meal, bone meal, humic acid, amino acids, and seaweed extracts and naturally-occurring organic fertilisers include manure, slurry, worm castings, peat, seaweed, humic acid, and guano.