University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Time for Fertilizing Lawns

September 2, 1999

With Labor Day weekend just about here, we begin the transition from summer to early fall. Early fall is an ideal time for fertilizing lawns. With all the fertilizer products in the garden center, how do you choose the right one?

When looking at the fertilizer bag, the three numbers represent nitrogen, phosphorus, and potassium, in that order. The main concern for lawns is adding nitrogen that helps give a nice green color. Potassium is used for hardiness of the plant, however, and is commonly found in winterizer fertilizers. Phosphorus is generally not needed in significant amounts unless a soil test has shown a deficiency.

An important portion of the product label is the guaranteed analysis that will tell more about the nitrogen and other nutrients in the package. Look for controlled-release nitrogen in the product. Controlled-release nitrogen, often referred to as slow-release or perhaps extended feeding on the package, will release smaller amounts to the grass over a longer period of time. This leads to more uniform growth.

Examples of controlled-release nitrogen to look for on the label include sulfur-coated urea, ureaform, coated urea, IBDU, and activated sewage sludge. Also look for water insoluble nitrogen, or WIN. These are all examples of good fertilizer sources for use on lawns. Although more costly, controlled release nitrogen fertilizers are highly suggested for lawn use.

After purchasing a quality fertilizer, how much should be applied to a lawn? Amounts are based on the nitrogen rate, which varies according to the type of grass and maintenance level. An average full-sun lawn in our area should receive about three pounds of nitrogen per 1,000 square feet of area per season. Some should get less, especially lawns in shady areas. Higher maintenance lawns may need more.

Most individual applications should be around one pound of nitrogen per 1,000 square feet. This early fall treatment could be higher, in particular if some type of controlled release nitrogen fertilizer is used. Fertilizer labels often have suggested setting guides and also indications on the lawn coverage the bag will provide.

Whether fertilizing once, twice, three times or more a season, early September is a key time. If the lawn is dry, fertilize right after a rain or irrigate ahead of time for the best results.


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