What is good for our yards may be bad for our lakes. Lawn fertilizer can become pollution that disturbs the natural balance in a lake or stream. Fertilizing the lake leads to an ugly explosion of plant and algae growth (blooms), often followed by a massive die-off with the dead vegetation decomposing in the water. This high rate of decomposition uses up the oxygen supply in the water, depriving fish of the oxygen they need to breathe and causing fish kills. Certain algal blooms can even be directly harmful to us if we swim in them. So, fertilizers in our lakes and streams create a big, messy problem. By taking a few smart steps in yard fertilizing practices, this pointless personal pollution can be prevented.

Read the Label

The best place to start with fertilizer use is to read the label. All bags of fertilizer have three numbers on them (i.e. 15-0-15). The first number is the percentage of nitrogen, the second is the percentage of phosphorus, and the third is the percentage of potassium. All labels are required by law to have these numbers posted. The number you want to pay the most attention to when it comes to fertilizing your lawn is the middle number - phosphorus.

Phosphorus - you don't need it!

Choose lawn fertilizer that is very low in phosphorus. Zero is even better. Phosphorus is causing serious problems - it is extremely difficult and expensive to remove once it gets into the water. Most north Florida soils are already high in phosphorus, so paying for it in your lawn fertilizer is unnecessary. Even if a soil test suggests the use of phosphorus, it is still not needed on your grass, because phosphorus is only important to flowering plants and, in our area, is a waste of money on a healthy lawn.

It is actually okay not to fertilize at all and it certainly isn't necessary to fertilize routinely. Most lawns can draw the nutrients they need from the clippings that fall back into the grass after mowing. Bagging these resources and throwing them away is unnecessary work that will be detrimental to your lawn in the long run. Fertilize only in response to a determined need and remember, "less is best."

Important points in fertilizing the grass:

• If you decide you need to fertilize occasionally, make sure that at least half of the nitrogen in your fertilizer is slow-release or water insoluble nitrogen. Slow-release fertilizers are less likely to leach out or wash away in water runoff. Apply no more than 1 pound per 1,000 square feet of lawn.
  
  NOTE: It takes about 6.67 pounds of 15-0-15 fertilizer to supply 1 pound of nitrogen for that size area. If you are not using a slow-release fertilizer, never exceed a rate of ¸ pound of nitrogen per 1,000 square feet of lawn (about 3.33 pounds of fertilizer). For other fertilizer calculations, check with your County Extension Service. See Additional Resources section on page 10 for phone numbers).
  
• What type of grass do you have? Centipede needs very little nitrogen fertilizer. In fact, the most common problem with Centipede is over fertilization, which leads to a disease called Centipede decline.
  
• Fertilize no more than once or possibly twice each year (April and August).
  
• When applying fertilizer, use a low spreader setting so that you can make at least two passes (in a crisscross pattern) before you run out of fertilizer. Remember that your impervious surfaces like sidewalks, streets, or driveways don't need fertilizing and anything that lands there will be washed off to our waterways with the next rain.
  
• If your lawn borders a lake, pond, stream or river, keep the fertilizer far away from the water, unless you want to watch your clear water turn a slimy green.
  
• It's important that you "water-in" the fertilizer yourself with just about 1/4" to 1/2" of water. If you depend on a rainstorm to do the watering, you may get a nasty surprise - a gully washer that washes all of the fertilizer, and your hard work and money, down the nearest storm drain. Or, it may not rain at all. Try to avoid counting on rain to "water-in" the fertilizer, because rain is hard to predict.
  
• Never fertilize before a storm. Delay application if rain is expected.

Mature shrubs and trees usually don't need to be fertilized, particularly if they are well mulched. Fertilize younger shrubs and trees only as needed to make them grow faster, no more than three applications per growing season.