What Do the Numbers Mean on a Bag of Fertilizer?

Have you ever wondered what the numbers mean on a bag of fertilizer? It is important to understand the numbers on the fertilizer, what they represent, and how they can apply to your lawn care.

The first number on the bag represents Nitrogen (N). A lot of people associate Nitrogen with simply making the grass green. That’s true, but Nitrogen is also important in making the grass grow straight and strong. Without enough Nitrogen the grass’s growth will be stunted and it will not appear green and healthy.

The second number on the bag represents Phosphorus (P). If Nitrogen is what is helping your lawn above ground you can think of Phosphorus as helping your lawn below ground. Phosphorus strengthens the roots of your grass and helps the roots grow deep so that your grass becomes anchored. Without Phosphorus the lawn will pull up easily. Phosphorus also pairs well with Nitrogen to provide energy transfer below and above ground.

The third number on the fertilizer is Potassium (K). Remember that even though Potassium starts with the letter “P” it is represented on the periodic table of elements as the letter “K” so you will see “K” on the fertilizer representing Potassium. Potassium helps the lawn take up nutrients and water from the soil to keep the grass healthy and strong. With adequate Potassium a lawn will be less susceptible to drought, disease, extreme cold, and extreme heat.

How much of each number should I use and when?

Determining exactly which numbers of each element should be used is determined by a lot of factors, including location, elevation, and time of year. Generally you will want higher Nitrogen in the Spring and summer then come down slightly in the fall. Phosphorus will follow the same pattern as Nitrogen with the amount coming down in the fall and winter. Potassium will do the opposite and start low spring and summer and increase for all and winter.

To get your numbers dialed in exactly you will want to consult with a local nursery or professional that can get you on track. The friendly staff at Lawn Doctor is always happy to help you dial it in as well. There are many other considerations when fertilizing your lawn such as preventing weeds, preventing grubs, and even adding hydra guard to help against drought. Consultations with Lawn Doctor are always free if you would like to talk about your lawn specifically.