In addition to light, air, water and space for roots, growing plants need a supply of nutrients — elements necessary to carry out their life process. Some of these nutrients, the ones referred to as trace elements, are needed in infinitesimal quantities that most soils can supply. But there are three major nutrients—nitrogen (chemical symbol N), phosphorus (P), and potassium (K)—that plants need in larger amounts for consistently good growth.

Every fertilizer’s label shows, in numbers, the formula of major nutrients; the guaranteed analysis information specifies the nutrient percentages and mentions their chemical sources.There is not one specific fertilizer that can be used in all months of the year. Changes in weather and soil temperatures dictate different fertilizers for the various seasons.