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The optimal time to apply fertilizers is when the grass roots and blades are actively growing. Apply fast-release fertilizers at a rate of 1 pound of nitrogen per 1,000 square feet. Slow-release fertilizers usually require a higher rate of application. Follow the manufacturer’s instructions; check the calibration of your spreader, as well as the square footage of your lawn, to ensure that you are applying the right amount. Remember, more is not necessarily better with fertilizers, applying too much may “burn” your lawn and promote thatch formation, disease, and insect infestation.
Keep in mind that well-watered lawns or those subject to heavy rainfall will require more nitrogen. Sandy soils are more prone to leach nutrients, but using water-insoluble fertilizers will help nutrients remain in the soil longer. Grass clippings left on the lawn over the course of a year will add about 1 pound of nitrogen per 1,000 square feet, so you can plan accordingly. The basic guidelines of fertilizing include:
- Test soil to determine grade and amount of fertilizer to use.
- Apply no more than 1-pound of fast-release nitrogen per 1,000-square feet in a single application.
- Use slow-release nitrogen whenever possible, especially on sandy soils.
- Use only the amount called for based on your lawn’s square footage.
- Use a rotary spreader to apply quickly and evenly, and to avoid a striped pattern in the grass.
- Spread the fertilizer in two directions for each application.
- Apply fertilizer to dry grass, and water well immediately afterward.
- Sweep up any fertilizer spilled on paved areas and save for later use.
- Do not use leftover lawn fertilizer on trees, shrubs, annuals, or perennials. Too much nitrogen on these plants stimulates stem and leaf growth, decreases flower and fruit production, and sends an open invitation to chewing and sucking insects that feed on the nitrogen-rich foliage.
Growth season occurs during the early to mid fall, when weed competition is minimal, and fertilizing produces healthy roots. This timing also allows plants to build up on needed carbohydrate stores with just a moderate amount of top-growth. You should divide the annual amount of fertilizer and apply two-thirds in early fall and the remainder in mid to late spring, after the lawn’s initial green-up. For low-maintenance lawns, apply 2 pounds of nitrogen per 1,000 square feet. This may require an adjustment, given your specific growing environment, soil test results, the lawn’s condition, and the type of fertilizer you use. For example, Kentucky bluegrass and Perennial ryegrasses require more fertilizer than the fescues. Consult your local Cooperative Extension Service (CSREES) for recommendations.
Southern lawns have a larger blade size, grow more vigorously, and need at least two applications of fertilizer each year. Do the first application about three weeks after the initial spring green-up; then fertilize again in late summer. Wait until warm-season grass becomes dormant before fertilizing areas overseeded for winter color. You can add supplemental quick-release nitrogen in between if there is weak growth and poor color. For low-maintenance lawns, apply 2 to 4 pounds per square foot. This may require adjustment depending on your specific growing environment, soil test results, the lawn’s condition, and whether you use a slow or fast-release type of fertilizer. For example, Bermudagrass, Zoysiagrass, and St. Augustinegrass need more fertilizer than Bahiagrass, Centipedegrass, or Carpetgrass. Consult your local Cooperative Extension Service (CSREES)
The nitrogen fertilizers listed below are commonly available at nurseries and garden centers:
- Ammonium nitrate
- Ammonium phosphate
- Ammonium sulfate
- Calcium nitrate
- Activated sludge
- Alfalfa meal
- Bone meal
- Composted manure
- Dried poultry waste
- IBDU (isobutylidene diurea)
- Methylene urea
- Soybean meal
- Sulfur-coated urea
Learn more: What is organic fertilizer?