NewsWhen fertilizing lawns, two crucial aspects to consider are how much to use and when to apply it. Most full-sun lawns (Kentucky bluegrass; Kentucky bluegrass combined with perennial ryegrass and/or fine fescue) in northern Illinois need around three pounds of nitrogen per 1,000 square feet every growing season (recommended range is 2 to 4 lbs./1,000 sq.ft./season). Split into two or three applications, with each application containing around one pound of nitrogen per 1,000 square feet.
To Figure How Much Nitrogen Fertilizer to Apply to Lawns:
- Divide the required nitrogen rate by the percentage of nitrogen in the bag. (first number of 3 on bag, use decimal form)
- Multiply the answer by the square footage of the grass and divide by 1,000.
EXAMPLE: 15-5-10 fertilizer, 7,000 sq ft, 1 pound nitrogen/1,000 sq foot
- 1 pound divided by .15 = 6.66, round to 6.7
- 6.7 multiplied by 7,000 is 46,900; divided by 1,000 equals 46.9 pounds.
As a result, about 47 pounds of 15-5-10 fertilizer are required to cover the whole grass.
After determining how much to apply, the next critical choice is when to apply. In northern Illinois, early autumn (September 1-15) is an important period for fertilizing lawns. The timetable below specifies when to apply depending on the number of applications to be made each year and the desired grass condition. In May and September, use controlled-release nitrogen fertilizers, and in late autumn, use a fast-release source. (Refer to Choosing Fertilizers for Your Lawn) Consider Mother’s Day, Labor Day, and Halloween as reminders or good times to fertilize your lawn in northern Illinois.
Lawn Fertilizing Program Schedules for Northern Illinois
| Number of Applications/Year | Suggested Timing Schedule |
|---|---|
| One (low quality lawn) | Early September |
| Two (low to moderate quality lawn) | Early May, Early September |
| Three (moderate to high quality lawn) | Early May, Early September, and Late October/Early November are all good times to visit. |
| Four (only with irrigation)(high quality lawn) | Early May, Mid-June, Early September, and Late October/Early November are all good times to visit. |
Composts are used in an organic fertilizer program at least once a year and may be augmented with compost teas if desired.