Good maintenance type fertilizers should be in a 3-1-2 ratio of nitrogen (N) to phosphorus (P) to potassium (K). An example of a 3-1-2 ratio fertilizer would be a 15-5-10 or something relatively close to this. However, keep in mind that established lawns do not require additional phosphorus (the middle number) and should be avoided. Requirements for phosphorus and potassium (the third number) should always be based on a soil test. Nitrogen only fertilizers with some slow-released nitrogen (See Guaranteed Analysis on bag) can be used if phosphorus and potassium are at adequate levels.
Most lawn fertilizer products are designed to cover 5,000 or 7,500 square feet. Check the bag and read the label of the product you have chosen. It is important to apply the correct amount of fertilizer per total square footage of your lawn. Any remaining fertilizer can be stored in a cool, dry place until next time. It is also best to apply one-half the rate in two directions to ensure an even distribution. Be sure to sweep or blow all fertilizer off of sidewalks and driveways into the lawn. This helps to maintain good water quality for your community.
Click here for more information about application timing and rates.
Click here for more information about spreader calibration.
Calculating fertilizer amounts based on nitrogen recommendations from an extension person, literature, or soil test report.
Enter the amount of nitrogen (N) you wish to apply per 1,000 square feet:
Enter the amounts (%) of nitrogen (N), phosphorus (P), and pottassium (K) in the fertilizer you selected. For example, a 24-4-12 would be the precentages of N-P-K.
You need ______ pounds of your selected fertilizer to cover your ______ square foot lawn.
The rate is ______ lbs of fertilizer per 1,000 square feet, or ______ lbs of fertilizer per acre.
Soil testing your lawn can prevent unnecessary fertilizer applications. Soil testing will tell you what nutrients the soil needs as well as what nutrients are in sufficient amounts. Knowing the pH of the soil is also important for nutrient availability to your lawn. Applying only what is needed also helps maintain good water quality for your community.
Click here for information on soil testing lawns.
Direct questions and comments to Kent Shannon
Option 1 - Go to "Google Map Developers Area Calculator" click here. You will be leaving the fertilizer calculator app to use this area calculator. Be sure to subtract your home and any other hardscapes from the total area to determine the area of your lawn, then return to the fertilizer app.
Option 2 - Actually measure the size of your lawn with a measuring tape. Your lawn can be broken into multiple geometric shapes, measuring each one, then summed for the total area.
Option 3 - Pace-off the lawn area to estimate square paces. Your lawn can be broken into rectangles or squares, paced and summed for the total square paces. Then multiply square paces by 6.25 to equal square feet. Average normal pace is 2.5 feet.
Table 1: Fertilizer Recommendations for Tall Fescue, Kentucky Bluegrass and/or Perennial Ryegrass based on amounts of nitrogen
| Expressed in pounds of nitrogen per 1,000 square feet | ||||
|---|---|---|---|---|
| September | October | November | March/April | |
| Basic Maintenance | 0.75 to 1.0 | + 0.75 to 1.0 | + 1.0 | + 0.5 to 1.0 |
| Low Maintenance | 0.75 to 1.0 | + 0.75 to 1.0 in Oct. or Nov. | -- | |
Table 2: Fertilizer Recommendations for Zoysiagrass, Bermudagrass or Buffalograss based on amounts of nitrogen
| Expressed in pounds of nitrogen per 1,000 square feet | ||||
|---|---|---|---|---|
| May | June | July | August | |
| Basic Maintenance | 0.5 to 0.75 | +0.5 to 0.75 | +0.5 to 0.75 | +0.5 to 0.75 |
| Low Maintenance | 0.5 to 0.75 | -- | +0.5 to 0.75 | -- |
Table 3: Fertilizer options to adjust phosphorus or potassium only
| Phosphorus (P) Source | Potassium (K) Sources |
|---|---|
| Triple Superphosphate (0-45-0) | Potassium sulfate (0-0-50) i.e. Sulfate of potash or SOP |
| Potassium chloride (0-0-60) i.e. Muriate of potash |
This project was supported by National Integrated Water Quality Grant Program number 110.C (Award 2012-03652) and the Missouri Agricultural Experiment Station.
MU CAFNR
MU Extension