Two important factors to consider when fertilizing lawns are how much and when to apply. About three pounds of nitrogen per 1,000 square feet per growing season is suggested for most full-sun lawns (Kentucky bluegrass; Kentucky bluegrass mixed with perennial ryegrass and/or fine fescue) in northern Illinois (suggested range is 2 to 4 lbs./1,000 sq.ft./season). Split into two or three applications, with each single application of nitrogen being about one pound per 1,000 sq. ft. About half as much nitrogen is suggested for shade lawns. Percent nitrogen in the bag and size of the lawn (in square feet) are calculation variables as shown below.
EXAMPLE: 15-5-10 fertilizer, 7,000 sq ft, want to apply 1 lb. nitrogen/1,000 sq ft
Therefore, need about 47 pounds of 15-5-10 fertilizer to cover entire lawn
After calculating how much to apply, when to apply is the other important decision. Early fall (September 1-15) is a key time for fertilizing lawns in northern Illinois. The schedule below outlines when to apply based on how many applications are to be made annually and desired lawn quality. Use controlled-release nitrogen fertilizers in May and September and a fast-release source in late fall. (Refer to Choosing Fertilizers for Your Lawn) Consider Mother's Day, Labor Day and Halloween as reminders or favorable times to fertilize lawns in nothern 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, Late October/Early November|
|Four (only with irrigation)(high quality lawn)||Early May, Mid-June, Early September, Late October/Early November|
An organic fertilizer program involves using composts applied at least once a year and can be supplemented with compost teas, if desired.