Understanding Fertilizer Labels

Fertilizers are typically identified with three numbers. These three numbers are generally printed in large, bold characters on the fertilizer container and refer to the percentage of “primary” nutrients, nitrogen (N), phosphate (P), and potassium (K), in the container.  For example, a bag of 26-2-3 analysis fertilizer contains 26 percent nitrogen, 2 percent phosphate and 3 percent potassium. Therefore, a 50-pound bag of 26-2-3 analysis fertilizer would contain 4.42 pounds of nitrogen, 0.34 pounds of phosphorous, and 0.51 pounds of potassium.

Bag Weight % of Nutrients Pounds of Nutrients

17 lbs. x 0.26 = 4.42 lbs. of nitrogen

17 lbs. x 0.02 = 0.34 lbs. of phosphate       Bag weight  has a big influence on quantity of Nutrients applied

17 lbs. x 0.03 = 0.51 lbs. of potassium

                        5.27 lbs. (total weight of nutrients)

As illustrated in the above example, the total weight of the nitrogen, phosphate, and potassium will never equal the total weight of the fertilizer container. The remainder of the contents in a fertilizer container is comprised of a mixture of one or more “secondary nutrients” (i.e., calcium, magnesium, and sulfur ), “micro-nutrients” or as they are sometimes referred to as “trace”elements, (i.e., boron, chlorine, copper, iron, manganese, molybdenum, and zinc), and a filler material generally granular limestone.