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  Quick-Release vs. Slow-Release Fertilizers  l  Fertilizer Guidelines  l

Separate Fertilizing and Weeding  l  Additional Information

Quick-Release vs. Slow-Release Fertilizers

You may have heard that "quick-release" chemical fertilizers are adding to the pollution in Puget Sound, local streams, and ground water. But you want a nice green lawn... what can you use that will give you a healthy lawn and still protect water quality?

Choose a slow-release, natural, organic, or long-lasting fertilizer. These slow-release fertilizers are broken down gradually by microbes in the soil. They are made from bonemeals, fishmeals, composted manure, limestone, or rock phosphate. Because grass is able to use these nutrients over a longer period of time, less fertilizer is wasted by seeping into ground water or running off into streams. See the Fertilizer [PDF] garden guide for details on choosing a slow-release fertilizer.

Conversely, quick release chemical fertilizers are like junk food for the lawn — they give a quick jolt of energy but are not good for long-term health. Fertilizer can also wash off the lawn and into ground water, the nearest storm drain, or stream, adding unwanted nitrates to local water bodies.

Fertilizer Guidelines

Fertilizer bagLawn fertilizers are a mix of nitrogen (N), phosphorus (P), and potassium (K). The ratio will be printed on the package as three numbers (the first is nitrogen, the middle number is phosphorous, and the third is potassium). The recommended balance for lawn fertilizer is a ratio of 3-1-2. There are a few commercial fertilizers available that come close to this recommendation. Good proportions to look for are 10-2-6 or 5-2-4.

Apply natural, slow-release fertilizer in mid- to late May after the soil has warmed up enough to use the nutrients. Fertilize again in early September, and if you’re going for the “perfect” lawn, you can fertilize again in early November. More is not always better, over-fertilized lawns are more prone to disease, thatch, and drought damage. Always read and follow label instructions on the fertilizer bags.

Grass clippings left on the lawn every time you mow can supply up to half of a lawn’s fertilizing needs. In other words, don’t bother bagging the lawn clippings, leave them on the lawn to provide natural fertilizer every time you mow.

Separate Fertilizing and Weeding

Photo of green lawnWhen selecting a fertilizer, be aware that many brands add weed killer to create a “weed and feed” product. Even if you have weeds in your lawn, it is wasteful to spread a weed killer over the entire lawn. In addition to exposing children and pets playing on lawns to pesticides, the pesticides may be tracked inside where they don’t easily break down. For additional information, see Weed and Feed.

If you feel you must use a weed killer, spot spray weeds directly with the least-toxic product designed for your particular weed concern. Always read and follow label instructions since anything that kills weeds can also have health and environmental impacts.

Large numbers of weeds are a symptom of an underlying problem such as compacted soil, low soil fertility, the wrong grass for your growing conditions, or poor mowing practices. Improve your soil with compost and slow-release fertilizers; mow to 2 1/2 inches; and plant grass seed designed to thrive in the Pacific Northwest. Your lawn will look great and have the ability to out-compete weeds.

Additional Information

For more information on natural lawn care, what you can learn from weeds, and other gardening topics, contact Thurston County Environmental Health at 360-867-2674 or Email us.

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