Posted on 08 June 2009 by

What Do Those 3 Numbers on a Fertilizer Label Mean?

fertilizer-main_fullBy Vanessa Richins

If you’ve ever stopped to look at the fertilizer product shelf at the garden center, you may have wondered what the numbers on the front mean.

Never fear – it isn’t as complex as it seems.

First, the main number you want to look for is usually plastered across the front. You’ll see a series of three numbers separated by dashes, like 5-10-10.

These three numbers stand for the amount of Nitrogen-Phosphorus-Potassium and are abbreviated as N-P-K. The numbers are the percentages of the elements that are contained in that bag.

For example, if there was a 100 pound bag of this 5-10-10 mix, it would have 5 pounds Nitrogen, 10 pounds of Phosphorus and 10 pounds of Potassium. The rest of the bag is additional nutrients and fillers that make it easier for you to spread the fertilizer.

Nitrogen is important as a main contributor to good stem and leaf growth. Lawns are especially fond of nitrogen. One sign that your plants may need some nitrogen is if they start turning yellow.

Phosphorus is an element that helps in the production of flowers and fruits, so it is especially important for your vegetable and fruit plants.It also helps the plant strengthen its roots and resist diseases. If your plants need phosphorous, the leaves may start turning blue-green or purple.

Potassium works on developing disease and cold resistance into your plants, as well as aiding in stem development. When a plant isn’t getting enough potassium, the veins on the leaves may start turning yellow, while the leaf tips turn brown and start curling.

For your vegetables, a good general recommendation is to pick a fertilizer that has a ratio of 1-2-1 or 1-2-2. You figure this out by dividing the numbers on your fertilizer to the lowest possibility. Our 5-10-10 fertilizer would fit this, since you divide each number by 5, resulting in a ratio of 1-2-2.

One suggestion is that you should test your soil before adding any nutrients. It’s not as common, but too much of these nutrients could potentially harm your plants.

What other questions do you have about choosing a fertilizer?

One Response to “What Do Those 3 Numbers on a Fertilizer Label Mean?”

  1. Dan and Deanna Says:

    Thank you for letting us know what the numbers mean. They are very important to know.
    Dan and Deanna “Marketing Unscrambled”

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