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

August 31, 2000

With September arriving tomorrow, we begin the transition from summer to early fall. Early fall is an ideal time for lawn care, including fertilization. When fertilizing lawns, key decisions include choosing a quality fertilizer and applying the correct amount.

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

Look on the fertilizer package, usually on the back, for the guaranteed analysis. This section tells 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 for every 1,000 square feet of lawn 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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