Last year the U. S. Environmental Protection Agency’s Chesapeake Bay Program put together a panel of experts to look at lawns, lawn care, and the impact lawns have on water quality in the Chesapeake Bay.
The conclusion was that a “dense vegetative cover of turf grass” on a lawn reduces pollution and runoff. A thin sickly lawn dramatically increases pollution and runoff.
In recent years, increased use of fertilizers on home lawns and gardens has caused concerns about polluting the ground and surface water. In fact, the opposite is true. Research shows that a responsible program of lawn fertilization will actually improve water quality.
Environmental Benefits of Lawns
A properly maintained lawn can provide many environmental benefits including:
- Reduced soil erosion. Up to 90 percent of the weight of a grass plant is in its roots, making it very efficient in stabilizing soil and preventing erosion.
- Reduced run-off by slowing down water as it flows over property. Healthy, dense lawns can absorb rainfall six times more effectively than a wheat field and four times better than a hay field.
- The cooling effect of an average size lawn is equal to about 9 tons of air conditioning, greater than a typical home’s central air conditioning unit.
- Turf grass traps much off the estimated 12 million tons of dust and dirt released annually into the U. S. atmosphere.
- A turf area just 50’ X 50’ absorbs carbon dioxide, ozone, sulfur dioxide, and other gases and releases enough oxygen for a family of four.
Fertilizers and fertilizer ingredients
Phosphorus is one of the nutrients necessary for plant growth. Although misuse or misapplication may pollute lakes, proper application poses no threat of lake pollution. Inorganic phosphorus moves very little in soil, and when applied as a fertilizer it is quickly bound by soil. Phosphorus from lawn clippings and tree leaves left in the streets and gutters is soluble and a potential pollution source. Several years ago golf courses and lawn care companies voluntarily eliminated phosphorous from their applications with two exceptions. Those being when a soil test showed a deficiency, or when seeding or sodding a new lawn.
Nitrogen is present naturally in soils as nitrate ion, ammonium ion, and as a component of soil organic matter. Ammonium is readily converted to nitrate in the soil. Nitrogen generally produces the greatest growth response in plants of all fertilizer nutrients. Unlike phosphorus, nitrogen in its nitrate form is completely soluble and highly mobile in soil. It can thus readily leach downward and contaminate groundwater supplies. This can be prevented by frequent smaller applications of Nitrogen and the use of fertilizers containing SLOW RELEASE or organic Nitrogen.
Run-off Pollution from Lawns
The following are the most likely causes of run-off pollution from lawns:
- Over fertilization and non-judicious use of pesticides
- Applying fertilizers and pesticides just prior to heavy rain
- Leaving fertilizer and pesticide granules and grass clippings on impervious surfaces such as driveways, sidewalks, and streets where rainfall carries them directly to surface water
- Dumping of waste fertilizers and pesticides into storm drains
- Compacted soils leading to increased run-off of water rather than infiltration into soil
Overwatering leading to run-off and to increased leaching of nitrogen and pesticides
Best Management Lawn Care Practice Checklist:
- Apply enough water to wet the soil 4” to 6” deep without run-off occurring. Water again when the lawn shows sign of needing irrigation (darker bluish green cast; footprints left in the grass).
- Avoid excess irrigation that runs off the lawn; or leaches nitrogen out of the root zone. It is not necessary to wet the soil much deeper than 4” to 6” for most lawns.
- Avoid irrigating impermeable surfaces such as driveways.
- Check automatic irrigation systems on a regular basis for uniform watering.
- Core aerate lawns in September or April to relieve soil compaction and allow irrigation water and rainfall to soak in rather than run-off of the property.
- Leave grass clippings on the lawn to increase soil organic matter content and reduce the need to fertilize with inorganic fertilizers.
- After mowing, sweep or blow grass clippings from impermeable surfaces so rainwater does not carry them to surface water.
- Use sharp mower blades; mow Kentucky bluegrass at 3” tall and turf type tall fescue to 3.5” tall. Mow often enough so no more than one-third of the grass blade is removed at one time.
- Have a soil test taken to determine which nutrients are needed in what amounts.
- Do not over-fertilize. Apply the amount of nutrients plants need and time applications when turf grass is actively growing.
- Do not apply fertilizer to frozen soils.
- Calibrate fertilizer spreaders to ensure applying the correct rate.
- Do not fertilize sidewalks, driveways, and streets.
- Sweep or blow granules off impermeable surfaces and onto the turf so rainwater does not carry them to surface water via storm drains.
- Avoid fertilizing when heavy rainfall is in the forecast.
- Leave grass clippings on the lawn to increase organic matter content of soil.
- Select fertilizers with a combination of fast release and slow release nitrogen.
- Water in fertilizers soon after application.
- Core aerate lawns in September or April to alleviate soil compaction and encourage a healthy root system.
- Core aerate lawns in September or April if thatch exceeds one-half inch. Thatch is the reddish brown “mat” of rhizomes, root, and grass stems found between the soil and the grass.
- Use best management practices for a healthy turf that will be less susceptible to diseases, insects, and weeds.
- Positively identify lawn problems before selecting a control method.
- Use the least toxic approach that will effectively control the problem.
- Use pesticides responsibly.