We have always heard and believed that Nitrogen is the most important nutrient!! The fact is Nitrogen is just one of the important nutrients required by plants. However the producers of chemical fertilizers have somehow succeeded in convincing us that Nitrogen is the most important nutrient. To judge how important any element is; let us first understand the macro and micro nutrients required by plants. The following is a simplified version of the study of nutrients!
GROUP I : Carbon, Oxygen and Hydrogen : These are the most important nutrients without which the plants cannot survive for a long time.
GROUP II : Nitrogen, Phosphorous and Potassium : These are again very important nutrients required for flowering and fruiting of plants.
GROUP III : Calcium, Magnesium and Sulphur : These are required in little quantities however are important.
MICRO NUTRIENTS : All other elements fall into the micro nutrient category like iron, zinc, sodium, chlorine, copper, etc. They are required by plants in a very minuscule quantity.