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N-P-K: What Does It Mean?

By Jeremy Land on July 26, 2017 in BlogNo Comments

N-P-K: What Does It Mean? graphic

A lot of people are not sure what the numbers on a bag of fertilizer mean or what the ingredients do for the soil and turf. With that being said, if you’re in the field fertilizing yards every day, you should understand the importance of reading what’s in the bag.

NPK, or available Nitrogen-Phosphorous-Potassium, percentages are what the numbers represent. A bag of fertilizer that reads 17-5-9 has 17 percent available nitrogen, five percent available phosphorous and nine percent available potassium (by weight of the contents in the bag).

Nitrogen helps the turf green up and provides top growth by helping the plant produce more of what makes plants green—chlorophyll. Be prepared to mow more often as the turf will grow quicker!

Phosphorous helps roots grow dense and deep, as well as assists with flowering and fruiting. Without proper amounts of phosphorous, a plant will struggle to stay healthy because its roots will be weak due to fewer nutrients and water being taken up by the plant.

Potassium maintains the plants overall vigor and health. Without potassium, plants can’t perform their normal functions to survive and flourish!

In addition to these three nutrients, some fertilizers have micronutrients mixed into the bags, such as iron (Fe) at the end of the N-P-K. For example, 28-0-0 5 Fe has 28 percent nitrogen and five percent iron mixed in with it. Other micronutrients, such as sulphur (S) or zinc (Zn), may be mixed in the bag and will be listed accordingly.

Learn what your soil needs

Having your soil tested is the best course of action to take when you want to make your lawn as healthy and vibrant as possible. Knowing what it lacks will give you the best indication of what NPK ratio of fertilizer to use on your yard. If you don’t have a way to test it, your best bet is to use a well-balanced ratio (ex. 13-13-13) to make sure all parts are equal.

If you have questions, stop by your local Ewing to learn about soil testing options and what fertilizer may be best for your needs.

Jeremy Land photo
Jeremy Land
Author Jeremy Land is a service professional at Ewing’s S. Oklahoma City, Okla., location. He can be reached at jland@ewingirrigation.com or 405.364.9530.
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