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   Use Fertilizer Responsibly!

"A drop in the bucket." This often-used expression gives many people the excuse to resist change in their normal way of doing things. "Why change?" they say. "My actions mean nothing in relation to the total actions of everyone around me." This may have been true years ago, but today it's different. With the high concentration of people now living in the Mid-Atlantic region, the total cumulative effect is no longer "a drop in the bucket." Homeowners need to recognize those activities that are a risk to the environment and understand the practices that can help reduce those risks.

Fertilizer is important for a healthy lawn but only if applied in the proper quantities at the proper time. Misapplication of fertilizer can result in runoff to surface water or leaching to groundwater resulting in algal blooms and conditions that promote unhealthy water systems.

Fortunately, with a little knowledge and care we can fertilize our lawns for better growth and still maintain safe, healthy bodies of water.

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   Fertilizer is for FALL

The best time to fertilize most lawns is in the fall. In the Mid-Atlantic region most lawns are a mixture of cool-season turf grasses. Cool-season grasses grow best when temperatures are between 60 and 75°C. In the spring and early summer, most cool-season grasses (like Kentucky bluegrass, perennial ryegrass, tall fescue and red fescue) put resources into growing leaves. Everyone who cuts grass knows you have to cut the grass more frequently in spring and early summer. In most parts of the Mid-Atlantic, cool season lawns go dormant during the heat of the summer, unless they are irrigated. When fall rains return, the lawn comes out of dormancy, greens up and starts to grow. But, during the fall, resources are directed to root growth. By fertilizing your lawn from late August to early October, you are promoting root growth, which will result in a stronger, healthier lawn that is better able to tolerate stress during the rest of the year.

Another reason to concentrate lawn fertilization in the fall is there are fewer weeds that thrive during the fall. Summer annuals and broadleaf perennials that plague lawns do most of their growth in late spring and summer. By fertilizing in the spring, you promote weed growth. Fall fertilization promotes the lawn rather than lots of weeds.

Some people like to apply a little fertilizer in early spring for a quick spring green-up. There is nothing wrong with this practice. One half pound of nitrogen per 1000 square feet will be taken up readily by the lawn. But, don't apply fertilizer after April 30. If you fertilize in mid- to late-spring you will not only promote excessive leaf growth (that you have to spend extra time mowing!) but you might end up with lots of tender growth as the weather warms up in June and the lawn becomes susceptible to a whole host of diseases.

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   Fertilizer is a supplement, not a food

It is not surprising that most people think of fertilizer as plant food- in fact that phrase is often used on fertilizer bags. But, if we think back to high school biology, we remember that plants make their own food through a process called photosynthesis. Sunlight, water and carbon dioxide miraculously combine within plant cells to produce carbohydrates (sugars) and oxygen (a great side benefit for the animals on the planet!). The elements found in fertilizer (primarily nitrogen, phosphorus and potassium) are used by plants to combine with those sugars resulting in plant growth. Since fertilizer is often thought of as plant food, it is easy to understand why homeowners assume that declining lawns need a shot of fertilizer to improve their health. In fact, providing extra fertilizer during times of stress can cause the lawn to try to push growth when it should be conserving resources. It is better to think of fertilizer as a plant supplement that can be applied to assist the lawn when it is actively growing.

Of the 13 essential mineral elements necessary for growth, nitrogen (N), phosphorus (P), and potassium (K) are the principal nutrients applied to turf. Turfgrasses require N, P, K in a ratio of approximately 4-1-2. Thus, fertilizers with roughly this ratio are good for lawn maintenance. Fertilizer recommendations are usually given in terms of nitrogen requirements. Nitrogen is available as either water soluble nitrogen (WSN) or water insoluble nitrogen (WIN).

Most mixed fertilizers contain more than one source of nitrogen. The following is one example of a mixed fertilizer containing several different sources of nitrogen. This lawn fertilizer contains 30% of its nitrogen as WIN nitrogen.

Fertilization rate depends upon many factors such as N source, time of year, fertilizer requirement of species, and quality of turf desired. When using solely WSN, apply only one pound actual nitrogen per 1000 square feet per application. Apply fertilizers containing at least 30 percent WIN at rates of 1 1/2 pounds per 1000 square feet per application and fertilizers containing over 50 percent WIN at 2 pounds per 1000 square feet per application.

Most lawns require a total of 2-3 pounds of total nitrogen per 1000 square feet per year. Kentucky bluegrass lawns are heavy feeders and require the upper limit, while tall fescue lawns require the lower suggested rate.

N fertilizer recommendations have been given in terms of actual N. Fertilizers contain varying percentages of N. For example, a 12-4-8 fertilizer contains 12 percent N, so a 50 pound bag would contain 6 pounds N. At a rate of 1 pound N per 1000 square feet, the bag would treat a 6000-square foot area.

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   Recycle grass clippings

Grass clippings are an excellent resource for the lawn. They contain organic matter that improves soil structure and the health of the microorganism population in the soil. Plus they release nutrients as they decompose. Clippings represent about 1 1/2 pounds of N, 1/2 pound of P, and 1 pound of K over the course of a year. If you return clippings to the lawn, you can reduce the fertilizer added by those amounts.

Why do so many people go through the tedious and time-consuming task of collecting, bagging and disposing of grass clipping? Probably, because they've just always done it that way. It is true that if you wait too long in between lawn mowing sessions you can get very long clippings that clump up, exclude light and require raking. Mulching mowers help reduce this problem, but frequent mowing is the best solution. The single best strategy to achieve a healthy lawn is to mow it frequently and remove only one-third of the leaf growth with each mowing. Those clippings will sift down easily into the lawn and will not require bagging or raking.

Mowing the lawn is a significant stress, especially if you remember that lawns produce their own food and they need leaf tissue to do that. By removing lots of leaf tissue at one time, you stress the lawn and reduce the amount of food it can produce. If you mow the lawn every 5 days (during the growing season) and leave clippings, you will spend less time on the lawn than if you mow it once a week and bag clippings.

Thatch is a layer of partially decomposed tissue found at the soil surface. Contrary to popular opinion, thatch is not caused by grass clippings. The tough tissues of dead grass, such as rhizomes and stems, cause thatch. An accumulation of excessive thatch is caused by an imbalance between turf growth and decomposition rates. To prevent thatch buildup, keep turf growth and decomposition in balance. To control growth, avoid overfertilization and select slower-growing species. To enhance decomposition, encourage microbes by maintaining a pH between 6.0 and 7.0 and using a minimum of pesticides. Core aeration (removal of plugs of soil with hollow tines) will also enhance decomposition by increasing infiltration and aeration.

Some people bag grass clippings for use in another part of the garden. Grass clippings make good mulch for the vegetable garden and using them in that way is another form of recycling.

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