Fertilizer packages are labeled with three numbers that indicate the percentage by weight of the three nutrients most essential to plants. The order is always nitrogen, phosphate, and potash (potassium). Nitrogen promotes overall grass shoot growth. Phosphate supplies phosphorus, which promotes strong root growth. Potash supplies potassium and helps grass withstand stresses such as drought or disease. Recommendations provided with soil test results (see below) will tell you if you need to apply these three nutrients. If you do fertilize, try to keep the following in mind (MD CES):
• Try to keep fertilizer off of paved surfaces. If granular fertilizer gets onto paved surfaces, collect it for later use or sweep it onto the lawn.
• Use a drop spreader instead of a rotary spreader in restricted spaces, especially when near water, driveways, or sidewalks.
• Calibrate your spreader to make sure you are not over-applying fertilizer.
• Fill and wash spreaders over grassy areas, not on hard surfaces.
• Avoid getting fertilizer into natural drainage areas on your property.
• Never apply fertilizer to frozen ground or dormant lawns.
• Use fertilizers sparingly. Many plants do not need as much fertilizer or need it as often as you might think.
• Don't fertilize before a rain storm.
• Consider using organic fertilizers; they release nutrients more slowly.
• Use commercially available compost or make your own using garden waste. Mixing compost with your soil means your plants will need less chemical fertilizer and puts your waste to good use. Commercial compost and soil amendments may be available from your solid waste or wastewater utility as well as your local garden store.
Why is soil testing important?
Testing the soil for nutrients and pH is important to provide your lawn with the proper balance of nutrients while avoiding over application. If you are establishing a new lawn or landscaping, a soil test is strongly recommended. Soil testing takes the guesswork out of fertilization, is extremely cost effective, and can eliminate over-usage of fertilizers that contribute to non-point pollution in our streams.
How do I get my soil tested?
• Home testing: There are home test kits available for pH, nitrogen, phosphorus and potassium at local garden centers. These kits will give a general idea of the nutrients in your soil, but are not as reliable as lab tests.
• Outside organizations: services are available at land grant universities and other commercial testing services, providing more accurate results and more detail. There is also an option for requesting micronutrient testing if you suspect a problem.
• Landscaping Companies: Professional lawn care companies should test your soil before adding any fertilizers. Support companies that employ techniques to limit fertilizer use to the minimum necessary to maintain a green lawn.
How do I perform a soil test?
If you intend to send your sample to a land grant university contact the local Cooperative Extension Service for information and sample bags. If you intend to send it to a private testing lab, contact them for specific details before sending a sample. The following are some general guidelines for collecting a sample.
• Sample soil when the soil is moist but not wet.
• For each acre of land to be tested, 10-15 sub-samples are recommended. Areas that appear different or are used in a different manner should be sampled separately.
• Use a clean pale or container
• Clear away the surface litter or grass
• With a spade or soil auger dig a small amount of soil to a depth of 6 inches and place in the clean container.
• Mix the samples from each homogeneous land area together thoroughly and collect a sub-sample that will be sent to the testing facility.
• Send the sample immediately, and do not dry before sending.
How frequently should I test?
Testing should be done every two or three years. Sample more frequently if you desire closer monitoring of the nutrient levels in your lawn.
References and Resources
Center for Watershed Protection (CWP). 1999. Diazinon sources in runoff from the San Francisco Bay Region. Technical Note 106. Watershed Protection Techniques. 3 (1):613- 616. Maryland Cooperative Extension Service. Fact Sheet 702 - Lawns and the Chesapeake Bay. Morris, W. and D. Traxler. 1996. Dakota County Subwatersheds: Residential Survey on Lawn Care and Water Quality. Dakota County, Minnesota, Decision Resources, Ltd. USDA Natural Resources Conservation Service. 1998. Backyard Conservation: Nutrient Management. Washington, D.C..
• FEED THE SOIL
One of the most important things to do is to feed the soil by raking a half
inch or so of compost each spring and fall
• FEED THE GRASS
Leave grass clippings on the lawn. Clippings provide nitrogen and reduce amount of fertilizer by about one-half.
• RE-SEED ANNUALLY
To control weeds re-seed annually in the late summer or early fall. A thick new growth of grass will compete with the weeds for lawn nutrients and will eventually reduce weeds.
• MOW HIGH
Set your mower at highest setting and allow grass to grow between 3-to 4 inches high, allowing it to shade its roots ,conserve moisture and keep out weeds.
• WATER LESS BUT LONGER
Water, if needed, once a week in the early morning for several hours. Over watering can create an ideal environment for pathogens to thrive, leading to lawn problems.
• CONTROL YARD PESTS NATURALLY
Use natural insecticides and insecticidal soaps sprays to control pests or by application of beneficial nematodes.
