Confused about fertilizer numbers? What value do they have in organic gardening? A plant needs nutrients to survive. Most of these are provided by the soil, but soil varies tremendously in nutrient amounts, soil type, pH, and nutrient availability.
The three main nutrients that have been identified as absolutely necessary for plants are nitrogen (N), phosphorus (P) and potassium (K). These three are also known as macronutrients, and are the source of the three numbers commonly found on organic fertilizer labels. The numbers found on our All-Purpose Fertilizer, for example, are 5-5-5. This is the percentage by weight of the N, P, and K found in the fertilizer. (more…)