Commentary—

Going For The Green? Don’t Over-Fertilize That Lawn

By Joan Miles

Spring is here and people’s thoughts are turning to enjoying outdoor activities. One of those activities is lawn work. For many people this means making a trip to their local garden center and purchasing the first of a four-step fertilizer program. While that might seem to be the easiest plan, I would like to suggest a different approach.

What many people do not realize is the typical four-step fertilizer program for their lawns may contain more nitrogen than is needed for acceptable turf quality. Excess nitrogen in the soil is vulnerable to loss by leaching (percolation in the soil past the grass roots) and surface runoff in the form of nitrate. Nitrogen is the primary nutrient pollutant of drinking water wells and of rivers and streams that enter the Long Island Sound. With the increase of residential development and associated lawns and pavement, the chance of nitrate movement into receiving waters is increased from fertilized turf.

The good news is we can counteract this by changing our landscape practices. We can have nice lawns and still maintain good water quality by following some simple guidelines.

The first thing a homeowner should do is get a soil test available from University of Connecticut’s Soil and Nutrient Analysis Laboratory for $5 per sample. A soil test will tell you what nutrients are needed. This is important because it reduces the guesswork of deciding on how much fertilizer to apply. Without a soil test, it is more likely that excess fertilizer applications will be made and that can lead to nitrate leaching or running off into storm drains and ultimately into our water systems. This is especially true for our lawns because nitrogen is the primary fertilizer for lawns and applied in the greatest quantities.

If the soil test indicates that your lawn requires some nitrogen, it is best to use a slow-release form. A fertilizer with at least 50 percent of slow-release nitrogen is preferable. Slow-release nitrogen is available in organic fertilizers such as Milorganite or as synthetic products such as sulfur- or poly-coated urea. Slow-release fertilizers reduce the rate at which the nitrogen becomes available to plants. This results in the most efficient use of nitrogen since the plant gets only the amount of nitrogen it can use at one time.

Grass clippings returned to a lawn during mowing reduce the need for nitrogen applications by up to 50 percent. Clippings do not add to thatch build up if you are mowing your lawn on a regular basis. Remove no more than a 1/3 length of the grass blade when cutting your lawn. It is also important to keep your grass mowed to the height of two to three inches. Lowering the height of cut less than two inches results in a shallower root system, which translates to more water needed. The old saying, “cut it high, leave it lie” is an integral part to a healthy self-sustaining lawn. If you are mowing with a side-delivery mower, never direct the clippings onto driveways, sidewalks, or roadways; send them back onto the lawn. Clippings are very high in nitrogen and other nutrients and can be washed easily into storm drains. This further creates a pollution problem.

A general guideline is to use about one to two pounds of nitrogen per 1,000 square feet each year. Apply no more than one pound per 1,000 square feet at one time. Here is a basic schedule of application.

In April, before the forsythia stop blooming, apply a crabgrass inhibitor with no nitrogen added. An example of a pre-emergence herbicide is Barricade (prodicamine). Remember crabgrass treatments are a pre-emergent herbicide applied when the grass is dry so granules drop to the soil where this herbicide is active. Water it in after application. After using a pre-emergence herbicide to prevent crabgrass, avoid raking or aerating, which disturbs the protective chemical barrier.

In May apply your nitrogen that contains at least 50 percent slow-release nitrogen. You can also add Merit grub prevention later in May or early June if you have had a problem with grubs in the past.

In September or October (one or the other; not both!), another application of nitrogen (at least 50 percent slow-release) can be made to the lawn. It is critical not to apply after October 15. After this date, nitrate leaching losses increase greatly, but the nitrogen applied later than this dates does not provide any further benefits to turf quality.

During all of these applications, it is important to sweep up any fertilizer that falls on hard surfaces, like your driveway, walkway, or street, and return it to your lawn. Fertilizer left on hard surfaces wash quickly into storm drains leading to water systems. Also, remember to water lightly after fertilizing to incorporate the nutrients into the soil.

Another great way to reduce the maintenance required for a healthy lawn is to plant low maintenance turf types in your lawn. Turf-type tall fescues and fine-leaf fescues are well adapted to Connecticut’s climate and require less fertilizer, water, and pesticide applications. Turf-type fescues are good choices for high traffic areas. Fine-leaf fescues are not good in high traffic areas because they have poor wear tolerance. Whichever species of fescue you choose, make sure to use a blend of varieties within that species to avoid disasters. Planting only one variety creates a monoculture, and if that one variety is susceptible to a particular pest or disease, it might destroy your entire lawn.

A phrase coined by a master gardener working to promote sustainable lawns, “Fescue to the Rescue” is apt considering the advantages of this grass species. Fescues are preferable because they require less water, are more drought-tolerant, tolerate shade, require less fertilizer, tolerate low soil pH, maintain greenness during the summer, and maintain quality at higher mowing levels. Additionally, the turf-type tall fescues have high salt tolerance.

It is possible to have a beautiful lawn and landscape without applying excess fertilizers. A dark, green turf achieved by high nitrogen applications weakens the grass, decreases its health, wastes money, needs more frequent mowing, and hurts our environment by polluting our water. More details are available in a publication, Turf IPM and Nutrient Management, from Publications Resource Center Store at the University of Connecticut. Call 860-486-3336 or email store@canr.uconn.edu. You can also visit www.sustainability.uconn.edu to learn more about this topic.

(Joan Miles is a Master Gardener certified by the University of Connecticut and the Department of Agriculture. She lives in Sandy Hook with her husband, David, and their three children, Tyler, Jordan, and Devon.)