Why do we add fertiliser to soil and what is in it that plants need?

Fertilizer is added to soil to supply essential nutrients that plants need for healthy growth, particularly nitrogen, phosphorus, and potassium, often referred to as NPK. Nitrogen promotes leafy growth, phosphorus supports root development and flowering, and potassium aids in overall plant health and disease resistance. Additionally, fertilizers may contain secondary nutrients like calcium, magnesium, and sulfur, as well as trace elements necessary for various physiological processes. By replenishing these nutrients, fertilizers enhance soil fertility and improve crop yields.