Spring Lawn Care

Spring Lawn Care Is
High On Gardeners' Lists

Ed Perry
Farm Advisor

Lawn care, especially how and when to fertilize, is high on many gardeners' "to do" list these days. Here are some of the most common questions asked about lawn fertilization:

Q. How much fertilizer should I apply to my lawn at any one time?

A. Generally, a maximum of 1 pound of actual nitrogen per 1,000 square feet should be applied at one time when using a soluble chemical fertilizer for lawn fertilization. Nitrogen is the major element needed by grasses for growth, so it is the element upon which the application rate is based. Also, nitrogen is the most soluble element, and has the greatest potential for "burning" the grass if applied too heavily.

Q. How do I calculate how much of a fertilizer is needed to supply the 1 pound of actual nitrogen my lawn needs?

A. Simply divide 1 by the first number of the analysis shown on the bag (the first number always stands for the percent of nitrogen, by weight in the bag) and then move the decimal point two places to the right. For example, ammonium sulfate has an analysis of 21-0-0; 1 divided by 21 equals 0.0476. Moving the decimal two places right gives you 4.76 pounds of ammonium sulfate, which you apply to 1000 square feet of lawn.

Q. What's the best way to apply the fertilizer?

A. Fertilizing by hand can be effective, but a mechanical spreader is much easier and more accurate. Two types of mechanical spreaders are available: the broadcast (cyclone or rotary) type, and the drop spreader. Both can be equally effective, but correct use of the broadcast spreader will avoid striping, which is sometimes a problem with drop spreaders. You can apply the fertilizer most evenly by spreading half the total amount in one direction, and the other half in another direction.

Q. Should I wait for a rain to carry the fertilizer into the soil?

A. You should water the fertilizer in immediately after application. This may not apply to some slow-release fertilizers, especially those containing broadleaf weed killers. Watering in removes the fertilizer from the leaves, thereby reducing the possibility of foliage burn. Also, it washes the soluble nutrients, such as the nitrate form of nitrogen, into the soil where they will be absorbed by the lawn root system.

Q. Is fertilizing once a year adequate?

A. For most lawns, one application of fertilizer a year is not enough. Usually, two applications—in spring and again in fall, are minimum. However, if you only make one application, it should be in the fall on cool season grasses (like tall fescue, Kentucky bluegrass and ryegrass), and in late spring on warm season grasses (bermudagrass, St. Augustine grass). With once a year fertilization, a slow release product would be more effective than a soluble product.

Q. Can I use my fireplace ashes to fertilize my lawn?

A. Wood ashes are a good source of potassium, but it's unlikely that your lawn will ever be potassium deficient. Ashes supply almost no nitrogen, which is what your lawn mostly responds to. Ashes also are high in various salts which can burn your grass.

Q. How do I know if my fertilizer program is adequate?

A. If your lawn has good color, density and uniformity—in other words, looks good to you—your fertilizer program is adequate. However, if your lawn has poor color, or is being invaded by weeds, you may want to increase the amount and frequency of fertilizations.


Index for Home Horticulture

The author is Ed Perry, Farm Advisor,
University of California Cooperative Extension.

March 15, 1999