Review Version - Fertilizer Label

N-P-K

Since hydrogen, carbon, and oxygen are provided by air and water, we’ll now focus on three of the most common macronutrients that the plant roots absorb —N-P-K.

Fertilizers are labeled with three numbers that indicate the guaranteed analysis or the fertilizer grade. These numbers represent nitrogen (N), phosphorus (P), and potassium (K)—or N-P-K —and are often calculated based on the amount that’s immediately water-soluble meaning available to plants right away.

The three numbers give the percentage by weight of nitrogen (N), phosphorus (P) in the form of phosphate (P2O5), and potassium (K) in the form of potash (K2O).