Fertilisers contain nutrients that plants need. They can mostly be split up into macro-nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium and sulphur, as well as micronutrients such as zinc, iron, manganese, copper, boron, molybdenum and chlorine. Macro-nutrients are needed in larger amounts than micro-nutrients, which are equally important if they are lacking in the soil. Most of the organic fertilisers contain a good mix of both and they also add organic matter to the soil, which makes it more workable and fertile.