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Home / Learning Center / Topics / Fertilization / Lawn fertilizer facts

Fertilizer Facts

When to apply fertilizers

Leading scientists recommend applying nitrogen fertilizers to cool season grasses in the spring and fall only, since this is when the grass is actively growing. They recommend the application of 2.5 to 3.5 pounds (lbs.) of nitrogen per 1,000 square foot per year applied as follows to cool season grasses:

  • Spring (April–May) — The best time to apply fertilizer is after 3 mowings. Apply 0.5 to 1 lb. of nitrogen per 1,000 square feet to support growth and to build-up reserves for summer.
  • Summer (June–August) — Cool season grasses go dormant in the summer and do not require fertilizer until the temperatures drop with the start of fall. Warm season grasses grow all summer long and require an application of fertilizer to sustain this growth and remain healthy.
  • Fall (September–November) — The most important time to fertilize is in the fall to help the grass develop a strong root system. Apply 1.5 to 2.5 lbs. of nitrogen per 1,000 square feet (Use the higher amount if your lawn is Kentucky bluegrass or perennial ryegrass, soil is sandy, or grass clippings are not returned to the lawn.)
  • Late Fall (October–December) — an application of slow release winterizer fertilizer will benefit the grass plant as the roots continue to grow through the winter (until the ground freezes).  Be sure to look for a winterizer fertilizer with a high percentage of slow release nitrogen.

Understanding fertilizer numbers

The label on the fertilizer bag is required to show the percentage by weight of nitrogen, available phosphate (commonly referred to as phosphorus) and sulfate of potash (commonly referred to as potassium):

  • The first number is nitrogen, which promotes overall grass shoot growth
  • The second number is available phosphate (phosphorous), which promotes strong root growth
  • The third number is soluble potash (potassium), which helps grass withstand stress, for example, drought or disease

For example, a 24-2-8 fertilizer has 24% nitrogen, 2% available phosphate (phosphorus) and 8% soluble potash (potassium). Nitrogen, phosphorous and potassium are also sometimes referred to as N-P-K.

To understand how much of each nutrient is being applied to your lawn, you must multiply the weight of the fertilizer bag by the percentage of each nutrient. For example, a 30 lb. bag of fertilizer rated 24-2-8 has:

Nitrogen: 24% x 30 lbs = 7.2 lbs. Nitrogen
Phosphorous: 2% x 30 lbs = 0.6 lbs. available Phosphate
Potassium: 8% x 30 lbs = 2.4 lbs. soluble Potash

How many pounds of Nitrogen are applied?

Take the total pounds of nitrogen in the bag and divide by the number of thousands of square feet the bag covers. Since we have already calculated 7.2 lbs. of nitrogen above, we need the number of thousands of square feet. For the 5,000 sq. ft. yard bag used above, divide by 5 to get the per 1,000 sq.ft. rating. So, applying 7.2 lbs. of nitrogen per 5,000 sq.ft. results in 7.2/5, or 1.4 lbs. nitrogen per 1,000 sq.ft.

Two steps vs. four

Greenview Fairway Formula Fertilizers utilize patented time-released nitrogen technology developed for and used by over half the championship golf courses. One application in the spring and one application in the fall provides a complete annual feeding program.

The Spring Fertilizer with weed control is a unique product that combines both a crabgrass preventer and a broadleaf weed control herbicide with the university recommended amount of nitrogen (1 lb/1,000 sq. ft.). Seventy percent (70%) of the nitrogen in Greenview Fairway Formula Spring Fertilizer is time-released. This allows one application of Greenview Fairway Formula Fertilizer with weed control to replace both spring applications in a 4 step program.

Universities recommend no nitrogen be applied to cool season grasses in the summer because lawns go dormant due to heat. This is why you can mow less frequently in the summer. If you have a grub or insect problem, a pesticide without fertilizer should be applied after you discover the condition.

The Fall Fertilizer incorporates 1.5 lbs/1,000 sq. ft. of nitrogen. This is the minimum amount of nitrogen recommended by leading universities for the fall; however, because it is 40% time-released, one application provides feeding throughout the fall. This feeding rebuilds the grass root system and builds energy for a quick spring green-up!

Choosing a Product with Phosphorus

Some soils are high in Phosphorus. Therefore, additional phosphorus is not always needed. If you believe your soil is high in phosphorus, you should have your soil analyzed by your local state extension agency. To find your local state extension agency, look in the yellow pages or contact your local state university. Additionally, some counties mandate the use of products without phosphorus. Check with your local state extension agency for local regulations to make sure that phosphorus is allowed. 

View Greenview's full range of zero phosphate fertilizers »

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