Fertilizing the Yard — LESS is BEST

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.

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 ½ 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.
  • 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 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 ¼” to ½” 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.


Soil erosion occurs when water washes topsoil from your property. When this happens, you lose the nutrient-rich resource that your plants need to grow, and once topsoil washes away, it is very difficult to replace. Eroded soil clouds the water in lakes and streams and contributes excess nutrients that disrupt the balance of life.

Erosion depends on two factors: how much and how heavily rain comes down and how much cover is there to protect the ground. Trees and other plants keep heavy rains from knocking the soil loose and washing it away. Roots hold the soil in place so your yard stays at home.

To prevent erosion in your yard:

  • Plant a rain garden to slow the flow!
  • Don't leave exposed soil unprotected — use mulch to cover bare areas and try to establish plants or groundcover there. 
  • Direct storm runoff away from unprotected bare soil.
  • Consider terraces to slow the flow on steeply sloped places.
  • Schedule construction or major landscaping for the dry season.