The most common fertilizer ingredients are nitrogen, phosphorus and potassium. These macronutrients comprise the majority of the fertilizer. Their percentages vary according to soil composition and plant type. Fertilizers also contain secondary macronutrients and micronutrients in lesser amounts.
Nitrogen is essential to the cellular structure of plants. It is a building block of chlorophyll, DNA, enzymes and amino acids critical to plant development. It stimulates reproduction and leaf and foliage growth.
Phosphorus is necessary for photosynthesis. It encourages root growth, seed production and fruit formation.
Potassium is important for the growth of flowers and fruit and disease resistance. It aids photosynthesis, activates plant enzymes and is essential for building proteins.
Secondary macronutrients and micronutrients included in fertilizer in small amounts include magnesium, sulfur, calcium, boron and chloride. Other ingredients include copper and iron.