Lawn Care/Basics for Homeowners-Lawn Care/Fertilization

Please select among the following topics to learn more about fertilization

Amount of Fertilizer

Fertilizers

When to Fertilize

How Much to Apply

The Grand Principle: Enough Is As Good As A Feast

Soil Testing

Application and Spreading

Composting as an Alternative

(Arkansas) Fertilize Your Lawn: Keep it Green and Growing
http://www.uaex.edu/Other_Areas/publications/HTML/FSA-2114.asp

(Florida) The Good and Bad in Landscape Fertilization:
http://sarasota.extension.ufl.edu/Hort/Pubs/Fertiliz.htm

(Georgia) Fertilization for Lawns
http://pubs.caes.uga.edu/caespubs/pubs/PDF/B710.pdf

(Georgia) Composting and Mulching
http://pubs.caes.uga.edu/caespubs/pubs/PDF/c816.pdf

(Indiana) Don't Bag It!
http://www.agry.purdue.edu/turf/pubs/ay2.htm
Recycling grass clippings

(Kentucky) Principals of Home Landscape Fertilization
http://www.ca.uky.edu/agc/pubs/id/id72/id72.htm

(Minnesota) Responsible Fertilizer Practices for Lawns
http://www.extension.umn.edu/distribution/horticulture/DG6551.html

(Minnesota) Lawn Care Practices to Reduce the Need for Fertilizers and Pesticides
http://www.extension.umn.edu/distribution/horticulture/DG5890.html

(Minnesota) Manufactured vs. Natural Fertilizers
http://www.extension.umn.edu/info-u/plants/BG284.html

Amount of Fertilizer

The amount of lawn fertilizer that should be applied annually depends on a number of factors.

1. Homeowner desires: A dense, dark green lawn requires more fertilizer than a thinner, lighter colored lawn. Applying more fertilizer annually also means more mowing and irrigation. (Note that over application of fertilizer can also lead to more nutrients leaching to groundwater or in runoff to surface waters.)
2. Location: More fertilizer is needed to maintain the same turf quality in the warmer regions than in the colder regions because the longer growing season.
3. Species: Certain types of zoysia, buffalograss, or tall fescue require less annual fertilizer than species such as Kentucky bluegrass or perennial ryegrass.
4. Weather: Wet weather stimulates growth and requires more fertilizer than dry weather. The same is true for an irrigated lawn vs. a nonirrigated one.
5. Soil type: Turfgrasses grown on a very sandy or very heavy soil requires more fertilization (especially phosphorus and potassium) than on a silt loam soil.
6. Age and quality of existing lawn: New lawns need more fertilizer for the first few years to enhance density as does rebuilding a neglected or thin lawn.
7. Clippings: Clippings should always be returned to the lawn; removing clippings for composting or mulch necessitates more annual applications of fertilizer.

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Fertilizers

All fertilizers have a series of three numbers displayed prominently on the label. These numbers represent the percentage by weight of nitrogen, phosphorus (as P₂O₅), and potassium (as K₂O). For instance, a bag of 24-4-8 fertilizer will be 24% N, 4% P₂O₅, and 8% K₂O by weight.

Fertilizer burn

Though N, P and K are all important in maintaining a healthy turf stand, N will cause the greatest response. Most fertilizer recommendations for lawns are listed as lb. N per 1000 ft². Nitrogen fertilizers come in two basic forms: quick release (readily soluble) nitrogen and slow release (slowly soluble) nitrogen. Quick release nitrogen normally causes a response in a week or less, whereas slow release nitrogen will cause a response in three to 10 weeks or more. Quick release nitrogen is inexpensive and can burn leaf blades if applied improperly. Slow release N forms tend to be more expensive, but rarely burn leaf blades even when applied at temperatures above 85 °F. Both N forms can and should be used on lawns. Examples of slow and quick release N forms are listed below.

Both forms of N are sometimes blended in the same bag so quick release N gives a response shortly after application while the slow release N results in a more gradual and longer response.

The best way to determine how much phosphorus and potassium to apply is to follow the recommendations of a soil test. In lieu of a soil test, a general recommendation is to apply 1/4 as much phosphorus and 1/2 as much potassium as nitrogen. For instance, if you apply 4 pounds nitrogen per 1000 ft² per year, you should apply 1 pound phosphorus and 2 pound potassium per 1000 ft² per year.

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When to Fertilize

Fertilize lightly in spring and early summer, little to none in summer, and heavily in fall. A heavy fall fertilization program produces the healthiest turf throughout the year. Applying high rates of N in spring and summer stimulates excess leaf growth at the expense of root growth. This forces you to mow more often and reduces turf quality. High rates applied in spring and summer can also stimulate disease, weed, and insect activity.

The table below recommends lawn fertilization programs for the eastern midwest. The maximum program is for homeowners who want the greenest lawn, and are also willing to devote considerable time to mowing and irrigation. The minimum program is for those of us who are satisfied with a less attractive lawn (and less work). Keep in mind that the initial seven points listed at the top of this page will greatly affect your fertilization program. Adjust dates for the climate zone you are in. Start earlier and finish later in warmer climates. In colder climates begin later and finish earlier.

In addition to the applications listed in below, an April application of 0.75 lb. N per 1000 ft² is recommended where no previous fall application was made. Preemergence herbicides applications in April can be combined with nitrogen fertilization. If this is done, the May fertilizer application should be skipped. Professional lawn care companies often increase the number of applications while decreasing the rate of nitrogen per application. This gives a more gradual feeding of the plants and produces a high quality lawn.

How Much Fertilizer to Apply?

It is important to apply the proper amount of fertilizer. The following example explains how to calculate the proper amount of fertilizer to apply. The fertilizer bag usually lists recommended settings for most popular spreader models. If the setting is not listed, refer to "Calibrating a Fertilizer Spreader." Even if your settings are listed on the bag, calibrate your spreader to make sure it is still accurate. Settings gradually change over time because of wear.

For an automatic fertilizer application calculator, click here: (North Carolina) http://www.ces.ncsu.edu/cumberland/fertpage/fertcalc_intro.html or (Minnesota) http://www.math.umn.edu/~white/personal/fertcalc.html.

Click here for the Texas A&M Lawn Fertilizer Calculator:
http://aggieturf.tamu.edu/aggieturf2/calculators/fertsheet.html

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The Grand Principle: Enough Is As Good As A Feast

Excessive application of fertilizer at the wrong time is not simply "overkill"; it is waste. If X amount of fertilizer is what you need, 2X will not bring you twice as much growth or take effect twice as rapidly. It will simply waste your money burn your grass, run off into the gutters or stream, or infiltrate to contaminate the groundwater. Learn your real needs from soil testing and do what is necessary. Use the fertilizer you already have in the form of recycled grass clippings and compost.

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Page Updated June 29, 2005