The macronutrients needed for plant survival are: Nitrogen, Phosphorus, Potassium, Calcium, Magnesium and Sulfur.
Fertilizers, which are used to provide nutrients for the growth of plants are usually divided into three classes N, P and K which denote nitrogen, phosphorus and potassium. These elements are essential for photosynthesis to take place, either as elements that make up chlorophyll, or in the other processes involved. In addition to photosynthesis these micronutrients also play an active role in all other activities that take place in plant cells. Their presence in the right amount ensures proper growth of the plants and production of fruits, seeds, foliage, etc. for which the plants are grown.
The other three macro nutrients which are calcium, magnesium and sulfur are usually not added to the soil as fertilizers as plants do not need too much of them and most soils contain an adequate amount.