Organic Lawn Fertilization
The current “green movement”, with its interest in organic, sustainable gardening,
has grown to include a variety of lawn care practices, including use of organic
fertilizers derived from natural sources such as plant or animal wastes. Examples
of organic fertilizers include biosolids (e.g., Milorganite) and manure-based fertilizers.
As use of organic fertilizers becomes more widespread, understanding ways in
which they differ from conventional, inorganic fertilizers is important.
One pound of nitrogen (N) from an organic fertilizer almost never produces the
same result as one pound of N from a conventional fertilizer. Organic fertilizers
tend to contain complex N-containing compounds that must be broken down by
soil microorganisms before the N can be used by plants. This process occurs
slowly over a long period of time and the microorganisms use a substantial
portion of the N for their own growth.
Also see Fertilizer Basics, a Wisconsin Pollinators reference guide.
In general, in order to get the same result from an organic fertilizer as a conventional
fertilizer, one needs to apply approximately twice as much organic fertilizer. After
roughly 10 to 20 years of fertilization with an organic product, organic nitrogen will
accumulate in the soil to the point that grass will begin to require less fertilization.
Another major difference between organic and conventional fertilizers is that organic
fertilizers usually do not cause grass to green up as fast as conventional fertilizers do.
Greening is related to the amount of soluble N available to the grass. Typically,
conventional fertilizers have higher amounts of soluble N than organic fertilizers.
Some organic fertilizers contain no soluble N at all, while others may have up to 50%
of their N in a soluble form. Since the insoluble portion of N in organic fertilizers
becomes available through the action of microorganisms, N release in organic
fertilizers is slower, especially in spring and fall when soils are cooler and
microorganisms are less active.
The first step in going the organic route with an existing lawn is beefing up
weakened soil, which means starting with a soil test. That way you'll know which
nutrients are lacking and which organic amendments you'll need to incorporate.
For example, soil with a calcium deficiency can be top-dressed with gypsum; and
soil low in magnesium might need a healthy dose of the mineral langbeinite.
You will need to dig up samples from several different areas of your lawn (2 cups of
soil total), and mail them off to a lab to be analyzed. Call local nurseries and
university extension offices to see if they offer soil tests (both should provide
Once you know which amendments you need, you should prepare the lawn by
mowing the grass down to about 2 inches, pulling up weeds, removing thatch
(dead grass and roots that accumulate on the surface), and aerating (a power
aerator that pulls up plugs of soil can be found at most rental yards). This will
enable your soil to fully absorb any amendments you add.
Whatever the test results, you'll also want to spread a half-inch of compost on
the lawn to add essential organic matter to the soil. It's almost like a blood
transfusion. It improves soil structure—especially in clay or sand-heavy soil—and
is full of beneficial organisms, including bacteria, algae, fungi, and nematodes,
that keep your soil healthy.
Look for compost that is made up of decomposed organic plant material, similar
to the stuff you find on the forest floor. You can buy it at nurseries, or collect
your own yard waste in a backyard bin. Many municipalities have composting
programs, which provide information on how to compost and, sometimes, discounted
composting bins. It is also recommended speeding up your lawn's transition to
organic by brewing your own compost tea and spraying it on your lawn once a
month with a backpack sprayer or a watering can.
Make an initial application of an organic fertilizer to your lawn in late May or early
June (i.e., around Memorial Day). Application of a slow-release fertilizer at that
time will gradually produce N that can be used by grass all summer long. Consider
a second application of an organic fertilizer at the beginning of July (i.e., around
Independence Day), but only if your grass is still green and not under drought
Make a final application in early fall (i.e., around Labor Day). This final
application will help promote faster greening and faster growth the following spring.
If you leave clippings on your lawn as you mow, N will be released as the clippings
decompose providing the equivalent of one additional fertilizer application of N
during the year.
In general, when using an organic fertilizer, keep the following points in mind:
Applying an organic fertilizer at the labeled rate will not green your lawn
in the same way you have come to expect from using conventional fertilizers. A similar
greening can be achieved by applying an organic fertilizer at twice the labeled rate.
In addition to supplying nitrogen, an organic fertilizer will add more organic carbon
to the soil, which may improve soil structure and soil biological activity over the long
term, and allow you to reduce your fertilization after 10 to 20 years.
Use an organic fertilizer that contains some soluble N. This will lead to
quicker greening and will likely lead to more efficient use of N. Using a product with
soluble N is especially important for applications made in the spring and fall. The
soluble N content is listed on the label of every bag of fertilizer.
Most organic fertilizers contain phosphorus and have the potential to
contaminate surface and ground water if used improperly,even though they are
exempt from state restrictions on the use of phosphorus-containing fertilizers.
Always sweep fertilizer off of solid surfaces (e.g., driveways and sidewalks), and
avoid application directly into bodies of water or on frozen soils.
When it comes to mowing a naturally grown lawn, conventional wisdom still
applies. Cut it too short and it doesn't develop the strong, healthy roots it needs
to fend off weeds and disease. So find out the best height for the type of turf
Cool-season grasses, such as Kentucky bluegrass and red
fescue, prefer to be between 3 to 4 inches high; while warm-season varieties like
Bermuda grass can be maintained at 1 to 1 1/2 inches. Be sure to mow with a
mulching attachment or a mulching reel mower and leave the clippings where
they fall; they're a natural source of nitrogen as they decompose.
When it comes to conserving water, the good news is that organically-cared-for
lawns require less water than chemically treated ones, since the latter needs lots
of moisture just to digest all the synthetic fertilizers and pesticides fed to them.
As with any lawn, the key is to water infrequently and deeply, encouraging turf to
send down deep roots and making it less susceptible to drought and disease.
The best time to water is early morning, since it gives your lawn plenty of time
to absorb it and dry off in the sun.
Most lawns require about 1 to 2 inches of
water per week in summer. Use a rain gauge to measure how much water your
lawn's getting; and make sure your sprinkler water isn't being wasted on your
driveway or street.
The Life Cycle of Plants: Fertilization
The Spruce: How to Make Your Own Fertilizer
Pollination and Fertilization
4 Ways To Use Eggshells For Your Plants
10 Ways to Use Banana Peels in Your Garden