Colorado State University Cooperative Extension recommends fertilizing four times each year: mid-March to April, the second application in May to mid-June, another in mid-August to mid-September, and the final application in early October to early November. If the grass is healthy and you applied fertilizer in late fall, you can skip the first application in early spring.

The three numbers listed on a fertilizer bag tell you the amount of nitrogen, phosphate, and potassium the bag contains as a percentage of its weight. For example, 20-5-10 on a 10-pound bag means the bag contains 2 pounds of nitrogen (20 percent of 10 pounds), 1/2 pound of phosphate (5 percent of 10 pounds), and 1 pound of potassium (10 percent of 10 pounds).

To determine the amount of fertilizer to apply, first measure the lawn s square footage (length times width). Apply 1 pound of nitrogen per 1,000 square feet of lawn. Using the 20-5-10 example, you would
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