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Home / Learning Center / Topics / Fertilization / Understanding N-P-K

Understanding Fertilizer Ingredients and N-P-K Numbers

Guaranteed analysis

The label on all fertilizer bags is required to show the percentage by weight of nitrogen, available phosphate and soluble potash. This is called the guaranteed anaylsis of the fertilizer.

  • The first number is Nitrogen (N), which promotes overall grass shoot growth.
  • The second number is available Phosphate (P₂O₅), which promotes strong root growth.
  • The third number is soluble Postash (K₂O), which helps grass withstand stress, drought or disease.

For example, a 24-2-8 fertilizer has 24% nitrogen, 2% available phosphate and 8% soluble potash. Nitrogen, phosphate and potash are also sometimes referred to as N-P-K.

To understand how much of each nutrient is being applied to your lawn, you must multiply the weight of the fertilizer bag by the percentage of each nutrient. For example, a 30 lb. bag of fertilizer rated 24-2-8 contains:

N: 24% x 30 lbs = 7.2 lbs. Nitrogen
P: 2% x 30 lbs = 0.6 lbs. Available Phosphate
K: 8% x 30 lbs = 2.4 lbs. Soluble Potash

Selecting a fertilizer for nitrogen content

When it comes to assessing the nitrogen content of a lawn fertilizer, what is more important than the quantity of nitrogen is the “quality” of the nitrogen, or the form in which it is present. Most important is the amount of slow release nitrogen contained in the fertilizer. There are a number of articles and resources on our website about nitrogen and its importance in the overall fertilization program. Learn more about slow release nitrogen and the slow release nitrogen technologies that make up the Greenview Fairway Formula Fertilizers.

Choosing a fertilizer with phosphate

Some soils are high in phosphorus. Therefore, additional phosphate is not always needed. If you believe your soil is high in phosphorus, you should have your soil analyzed by your local state extension agency. Additionally, some counties mandate the use of products without phosphate. Check your local regulations to make sure that phosphate in a fertilizer product is permitted.

To find your local state extension agency, look in the yellow pages, contact your local state university. You may also refer to our list of state extension agencies.

If you live in a phosphate restricted area, for example near lakes or other waterfront areas, Greenview Fairway Formula Fertilizers are also available with zero phosphate content, and the same advanced slow release nitrogen technologies as our other fertilizers.

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