JoAnne Skelly: Fertilizing the lawn


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Mid-April is a good time to apply lawn fertilizer. The cool season grasses in Northern Nevada generally require two to five pounds of actual nitrogen (N) per 1,000 square feet per year. To reduce turf maintenance, you can apply two to three pounds of actual N per 1,000 square feet per year instead. Heavily used lawns may need the higher rate than those that get little traffic.

Fertilize no more than three times per year, generally half what is recommended on the label in April, full strength in late May to early June, and a final application in October. If you only fertilize once a year, do it in the fall. Avoid mid-summer fertilizer applications to avoid stressing the grass with too much growth in the heat of summer.

All fertilizers show a three number formula on the package. These numbers are the percentages by weight of nitrogen (N), phosphate (P2O5) and potash (K2O). A lawn fertilizer with an analysis of 25-5-10 has 25 percent N, 5 percent phosphate (P) and 10 percent potash (K). A 50-pound bag has only 12 pounds of actual N, 2.5 pounds of P, and 5 pounds of K.

The way to determine how much fertilizer to apply to 1,000 square feet to achieve the correct amount of actual N for the year is to divide the pounds of actual N desired by the percentage of N in the bag. Then, divide that by three to calculate how much per each seasonal application.

To apply a half pound of actual N in April using a product on which the N percentage (the first number) is 25, divide 0.5 pounds by 0.25, which equals 2. You would have to apply two pounds of the product to 1,000 square feet of turf to achieve 0.5 pounds of actual nitrogen. Labels may take this calculation into account in their directions.

Using a spreader, apply fertilizer first in one direction and then go across the initial application side to side to avoid the light stripes of missed areas.

I usually water the lawn two to three days before application and again immediately after applying the product. How do you decide which of the many fertilizer options is the best choice for you? Soil testing is a good place to start.

Here are two laboratories that do testing: Utah State University Extension USU Analytical Lab, Ag Science, Room 166, Logan, UT 84322-4830; phone 435-797-2217. A&L Western Laboratories Inc., 1311 Woodland Ave., Ste. 1, Modesto, CA 95351; phone: 209-529-4080. Call to find out what they require in a sample. A healthy lawn is more drought resistant.

JoAnne Skelly is Associate Professor & Extension Educator Emerita at University of Nevada Cooperative Extension. Email


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