Fertilizer is food for plants. When you buy it, it will be labeled with three numbers, like 10-10-10. Each of these numbers represents the content by percentage weight of three components: nitrogen, phosphorus and potassium. Each of these components does a different job to help your plants grow.
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| Photo: sxc.hu/egilshay |
The first number stands for nitrogen (N). Nitrogen contributes for foliage growth. The 10 means that it contains 10% nitrogen by weight. If you're looking for a lush lawn, you'll want to feed it a high-N fertilizer (and make sure your mower's in good condition, because you're about to get a workout!).
The second number represents phosphorus (P), which helps rooting and setting flowers buds. A 5-10-5 fertilizer would be useful for a plant in which you want to encourage flowering rather that leaves. Chemical fertilizers marketed as "bloom boosters" are high in phosphorus.
The last number is for Potassium (K) which contributes to the overall health and vigor of the plants. Potassium helps the plant be strong against diseases and insects, and against droughts and cold weather.
 Sample fertilizer label. Photo: Flickr |
A fertilizer with all the same numbers (10-10-10) is considered a “balanced” fertilizer, but that doesn’t mean that is what you want. Lawns and foliage want a high nitrogen (N) content; roses would like more phosphorus. If you give a plant like a tomato too much nitrogen, it will grow nice, big, fat, lush leaves, but might not provide you with much wonderful fruit. (And yes, tomatoes are technically a fruit).
If you noticed that the three numbers don't add up to 100, congratulations, you ARE smarter than a 5th grader (and you can tell Jeff Foxworthy we say so). In addition to the 10% by weight of nitrogen, phosphorus and potassium in a 10-10-10 fertilizer, there's also 70% fillers and other stuff to make up the whole weight. It probably says on the bag what the other ingredients are.
If you're still looking to fertilize your brain with more info, you'll probably find the video below, errr, growth inducing.
