Understanding Fertilizer Labels and NPK Numbers

If you are looking to fertilize your lawn, annuals, perennials, or vegetables you will notice that all fertilizers have certain NPK numbers. These numbers can be hard to interpret and used properly. How do you know you are using them properly if you do not know what fertilizer is in them?  In this article, you will learn what NPK numbers mean and how to use them in your yard.

N=the percentage of NITROGEN content in the product.

P= the percentage of PHOSPHORUS compound present.

K= the percentage of POTASSIUM compound present.

Each of these compounds work on improving different areas of the plant. Nitrogen (N) encourages foliage growth and green color on plants. Phosphorus (P) nurtures the root, bloom and fruit development. Potassium (K) will help the plants overall health and fights diseases. All plants will benefit from a combination of these fertilizers. That is why all fertilizers will have all three, NPK’s, in them; they will just be a different ratio.  For example, if you are growing leafy vegetables you may want a fertilizer with higher amounts of nitrogen. If you are growing flowers, you  should look for one with higher amount of phosphorus to encourage blooms.

The plant is lacking nitrogen if you notice the plant is short, and the leaves are pale green-yellow in color. If the plant has a dark green color and is stunted there may be a phosphorus (P) deficiency. If the older leaves become yellow with scattered brown spots, you probably have a Potassium (K) deficiency. With Potassium (K), the leaves tend to curl.

On the fertilizer label you will see numbers like 10-10-10 or 20-5-5. In 10-10-10, this means the amount of Nitrogen Phosphorus and Potassium are all the same. In the 20-5-5, there is 4 times the amount of Nitrogen.

Lastly, before you apply the fertilizer, you should have your soil tested. There is already Nitrogen, Phosphorus and Potassium in your soil, so it is a good to test it to see what is deficient.