Fall Fertilization of Lawns Fall, not spring, is the best time to fertilize lawns. Spring fertilization encourages crab grass and other annual weeds and encourages excessive top growth that needs to be mowed frequently and is more susceptible to insect and disease damage. Fall fertilization encourages vigorous root systems with plenty of stored nutrient reserves for next spring.
For those who fertilize three or four time per year, remember the holiday rule. Fertilize on Memorial Day, the Fourth of July, Labor Day and on Halloween. That way your lawn will have a constant supply of the nutrients it needs.
For established lawns, high nitrogen fertilizer is best. This means that the first number in the fertilizer analysis is the highest. Many fertilizers contain more than one form of fertilizer. These are divided into two types. One is water soluble nitrogen (WSN) which is nitrogen that is immediately available because it dissolves in water.
Water insoluble nitrogen (WIN) is slowly available to the grass. The water insoluble nitrogen may be in the form of sulfur-coated urea, urea formaldehyde, organic fertilizers or other compounds. The advantage of water insoluble nitrogen is that it does not leach readily and remains available to the plant for long periods. It is an excellent fertilizer for fall application.
Fall is also an excellent time to aerate turfgrass. Most companies are not as busy in the fall. Aerate the soil is compacted or thatch is more than ½-inch thick.
KSL Greenhouse Tip Larry A. Sagers Regional Horticulturist Utah State University Thanksgiving Point Office