Turfgrass Fertilizer Applications

By Mike Morrow, CEA-Ag,
Lamar County, Texas

Spring is when most people think of fertilizing lawns; however, warm-season turfgrasses, especially Bermuda grass and St. Augustine, benefit greatly from fall fertilizer applications. Lawns receiving a fertilizer boost in the fall are more winter hardy, have a more healthy root system, and green-up earlier next spring. Area lawns need all the help they can get after the last three hot, dry summers.

What kind of fertilizer should I use?
We recommend using a 3-1-2 ratio fertilizer. This means fertilizer that contains 3 parts nitrogen to 1 part phosphorus and 2 parts potassium. This 3-1-2 ratio will supply the correct proportion of the three main nutrients - nitrogen, phosphorus and potassium. Examples include 21-7-14 or 15-5-10 fertilizers. Depending on the fertilizer used, several micronutrients may also be supplied.

When should I fertilize?
Application should be sometime between September 15 and October 15. This will give plants sufficient time for growth and storage of nutrients prior to the first freeze an winter dormancy.

How much fertilizer should I apply?
Apply the fertilizer at a rate of 1 pound actual nitrogen per 1,000 square feet of lawn area. Using more than this at a time can promote excessive growth, turf diseases, and other problems. Nitrogen is very water soluble and excessive nitrogen can lead to nitrate problems in runoff during rainfall.

How do I determine the area or square footage of my lawn?
Measure or step-off your turfgrass areas in both directions. Be sure to include smaller areas next to driveways, sidewalks, and between houses.

Length(feet) x Width(feet) = Area

Example: 50 feet x 50 feet = 2,500 square feet

What is meant by actual nitrogen?
The numbers on a fertilizer bag or container represent the percent content of the three main nutrients. The first number always given the percent nitrogen (N), the second is percent phosphorus (P)a, the third percent potassium (K). For example, a 50 pound bag of a 21-7-14 fertilizer is 21% Nitrogen, 7% Phosphorus, and 14% Potassium. To figure the actual pounds of the nutrient just multiply the weight of the bag times the percent - 50 x 0.21 = 10.5 pounds of actual nitrogen in the 50 pound bag. The actual pounds of phosphorus and potassium are figured the same way and in this case are 3.5 pounds of phosphorus and 7.0 pounds of potassium.

At the recommended rate of 1 pound actual N per 1,000 square feet, a 50 pound bag of 21-7-14 fertilizer will cover 10,500 square feet. Most yards are not that large. It may be necessary to weigh out the amount of fertilizer needed and store the remainder in a sealed container in a cool, dry place.