When & How to Fertilize Your Lawn

Question: When and how much should I fertilize my lawn? I don’t want to overdo it and have fertilizer going into the water table!

Great question and thanks for your concern about our water table!

In a normal year (before COVID-19), one of the easiest options would have been to contact our Healthy Virginia Lawns (HVL) project for guidance on keeping your lawn and our water table healthy. For a small fee, Master Gardener volunteers would come to your home, take a soil sample, do an assessment of your lawn, discuss the type of grass or groundcover that will grow well, and recommend a fertilization schedule. Unfortunately, due to COVID-19, all HVL visits have been SUSPENDED until further notice.

You may have heard this before: a soil test is the best way to learn the specific fertilizer needs for your lawn. You can take a soil sample and send it to the Virginia Tech Soil Testing Lab for analysis; specific instructions are provided at https://www.soiltest.vt.edu. Here’s a tip: you can pick up soil test boxes and submission forms from a plastic tub located outside the the entrance to the Albemarle County Office Building, 460 Stagecoach Road, Charlottesville, VA 22902. This entrance is on the BACK of the 5th Street County Office Building.

The soil test results will provide information about the fertilization needs of your lawn. A handy spreadsheet can also be useful to determine the type of turf grass you have or whether and how much fertilizer might be needed. See: https://www.pubs.ext.vt.edu/SPES/spes-40A/spes-40A.html Soil tests are recommended every 3 years.

The best time of year to fertilize your lawn depends on the type of grass in your lawn. If you have cool-season grasses (grows better in Spring and Fall), such as tall fescue, Kentucky bluegrass, and perennial rye-grass, it is best to fertilize in the late summer/early fall from August 15th through November. If you have warm-season grasses (grows better in Summer), such as bermudagrass or zoysiagrass, fertilize from March to August.

Fertilizer can get into groundwater in two ways: runoff of rainwater into streams or leaching downward through the soil. When fertilizers leach into the soil, some of the contaminants are filtered before reaching groundwater. However, runoff from rainwater typically ends up directly into our waterways.

The best way to prevent fertilizer run off is by following the recommendations provided in a soil test analysis. A summary of management practices for prevention of runoff is listed below:

• Use the proper amounts, ratios, and types of fertilizer (making it more likely to be utilized by plants instead of leaching into the soil)
• Use a slow-release nitrogen fertilizer
• Time fertilizer applications properly based on the type of grass
• Add organic matter to improve soil structure in your lawn
• Use healthy soil & cultural practices; including weed control, proper irrigation, leaf management, dethatching & aeration, etc.

• Use Best Management Practices for water conservation:

o Do a site analysis of your landscape and calculate your runoff
o Take measures to reduce runoff by installing permeable pavement, collecting rainwater, leaving storm drains clear, and watering your lawn using drip irrigation
o Use a mix of vegetation in your lawn & group landscape plants by their water needs; e.g., use plants that love wet feet in a rain garden or riparian buffer.

For more detail, see the groundwater quality reference listed under Resources.

If you are interested in taking advantage of HVL in the future, check our website periodically to find out when the HVL project will resume. Visit: https://piedmontmastergardeners.org/…/healthy-virginia-law…/


“Groundwater Quality and the Use of Lawn and Garden Chemicals by Homeowners, Virginia Cooperative Extension,” 426-059, Virginia Cooperative Extension.

Lawn Fertilization in Virginia,” CSES-135P, Virginia Cooperative Extension.

Photo by Daniel Watson on Unsplash.