NPK fertilizers contain three basic ingredients in varying ratios, which are nitrogen, phosphorus and potassium, states Gardener's Supply Company. These fertilizers provide the three basic chemicals that plants need from the soil to grow.Continue Reading
Many different manufacturers produce NPK fertilizers, all of which list the NPK ratio of these three chemicals on their product packaging, notes Gardener's Supply Company.
The ratio is listed on the packages as a series of three numbers separated by dashes. The first number listed is always the amount of nitrogen in pounds. The second number is the amount of phosphorus and the third number is the amount of potassium, both in pounds. For instance, a 15-pound bag of NPK fertilizer with the ratio 5-5-5 contains 5 pounds of nitrogen, 5 pounds of phosphorus and 5 pounds of potassium.Learn more about Agriculture