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Fall is the Time to Feed your Lawn!

University of Minnesota Extension, Stearns County News
October 4, 2017

Source:  Brenda Postels
Interim Extension Educator-Horticulture
University of Minnesota Extension
Stearns & Benton Counties

Fall is the Time to Feed your Lawn!
By Brenda Postels, University of Minnesota Extension

ST. CLOUD, Minn. (10/04/17) — In Minnesota, most of the lawn grasses we grow are considered "cool-season" and grow best in spring and fall.  As we move into fall, and our grasses are again actively growing, consider feeding your lawn. Just like people, lawns need a balanced diet. If you fertilize them too much, too little, use the wrong kind, or at the wrong time, they won't be healthy.

First of all, test your soil.  A soil test will tell you how much phosphorus (P) and potassium (K) fertilizer your lawn needs, if any. Visit or contact your county U of MN Extension office for soil testing information.  If tests indicate that no P or K is needed, use nitrogen fertilizers that contain few or none of these elements.  Adjust pH if needed.  Lawns should have a slightly acidic pH (6.0-7.0).  If your soil tests fall outside this range, follow instructions included with the test results for adding lime or sulfur to bring pH into this range.  If phosphorus and potassium levels are adequate in the soil, nitrogen (N) is the most important nutrient for grass growth.  For most low-maintenance lawns, a single application (1 pound/1000 square feet) between mid-August and mid-October (about two weeks after your last mowing) is best.  Top-growth continues in fall until there are about 10 days with average daily temperatures below 50° F.  Roots will continue to grow and take up fertilizer until the ground freezes.

Organic nitrogen sources alone are not a good choice for fall fertilization because they require warm soil and microbial action to release nitrogen.  Soluble nitrogen sources are readily available to the plant, but leaching may occur on sandy soils.  Slow-release to quick-release N is less risky to the environment.  Most synthetic lawn fertilizers contain at least 40 percent slow-release nitrogen.  Slow-release nitrogen sources have a lower risk of burning plants and a lower potential to pollute water than water-soluble N sources.  The tradeoff is that slow-release N is usually more expensive.  After applying fertilizer, water it in.  Give your lawn one-quarter to a one-half inch of water after spreading fertilizer to get the material into the ground where it can be used by plants. 

Consider different needs.  High-traffic areas usually require more fertilizer than low-traffic areas.  Different species of grass have different needs, too.  Kentucky bluegrass, for example, requires more nitrogen than do fine-leaf fescues.  If bluegrass doesn't get enough nitrogen, it is less competitive against weeds and pests.  If fine-leaf fescues (which normally grow slowly) get too much N, they produce lush, weak growth that is susceptible to pests.  Apply with care.  The idea is to get the right amount of fertilizer on the lawn and none into streams and lakes.  Feeding your lawn properly this fall will help to ensure a thick, healthy lawn next summer!   Always read fertilizer labels carefully before buying and again before using these products.  For more information, go to:

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