How to Read a Fertilizer Label
On the back of a bag of fertilizer, you will find three numbers. These three numbers tell the percentage of the primary ingredients in the fertilizer. Take a basic lawn fertilizer, for example, with a label that contains:
These numbers stand for the "big three" nutrients that your lawn needs to thrive. They always appear in the same order: nitrogen, phosphorous and potassium. They tell you how much of these nutrients, by weight, you are getting in the fertilizer. In this case, you are getting four parts nitrogen to one part phosphorous and two parts potassium.
If you don't want to know a lot about fertilizer, remember that nitrogen is the most important nutrient and it is the ingredient that makes your lawn green. To figure out how much nitrogen is in this bag of fertilizer, multiply its number (in this case, 20) by the weight of the bag of fertilizer (usually 50 lbs.). This means you are getting 10 pounds of nitrogen in this bag of fertilizer. This is important to know when you spread your fertilizer. You do not want to apply to much nitrogen - only one pound or less in any single feeding. Too much nitrogen can burn your lawn.