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Composting for the lawn

Published February 9, 2012

URBANA — Garden waste is perfectly good organic matter that can be returned to the soil.

"It is easy enough in our vegetable garden and flower beds where there is a lot of open space each spring that allows the gardener to turn in the compost, but what about the lawn, which deserves that organic matter too," said University of Illinois Extension horticulture educator Richard Hentschel. "Organic matter coming out of compost bins and piles can be used to top dress our lawns just like we use black dirt."

In the beds, gardeners do not worry about the occasional big pieces that have not completely decomposed. They either return them to the compost pile or turn them into the bed to finish breaking down.

For use on the lawn, however, screening the compost using a homemade sieve will make your top dressing job a lot easier.

"It is easy enough to fashion your own screen using one-by-four or two-by-four lumber, creating a frame that sits over the edges of your garden cart or wheelbarrow," Hentschel said. "Use hardware cloth that has one-half inch openings and cut it to size and secure it to the wooden frame using nails or staples. This screen can be very basic or a work of garden art, depending on your skills."

The better-composted material will probably be near the bottom and center of the compost bin or pile, where temperatures and moisture are consistent throughout the composting cycle. "Nearly all of that material should easily pass through the screen without a lot of additional effort or will not need to be screened at all," said Hentschel.

Material from the top and outside edges of the compost pile will have seen considerable temperature variation and may have dried out, slowing or stopping the composting process. Anything that does not pass through the screen should be saved and used at the next composting cycle.

Once the organic matter has been screened, it can be spread on the lawn. Except on a thinned lawn where the soil is exposed, the top dressing should go unnoticed by the neighbors.

According to Hentschel, "It is better to apply two or three lighter top dressings a season than one heavy one. You want to encourage new crown and root development and the active breakdown of the thatch layer to allow roots to develop and grow into the soil and not the thatch layer." Organic matter will continue to break down in the lawn, releasing the nutrients that the grass plants need to grow.

Once the top dressing has been applied, overseeding is the next step. Lightly rack the seed into the newly spread compost. Keep in mind that overseeding should be done when the soil temperatures promote quick germination. Depending on the contents of the compost pile, gardeners may later see an out-of- place plant, such as a tomato or cornflower, in the lawn or the flower beds.

Hentschel said that there will be big benefits as the weather turns warm. The grass will stay green longer and use less water because organic matter holds more soil moisture while improving drainage. "A healthier lawn is better able to recover from dormancy, a hot summer drought, a seasonal outbreak, or the badminton match from the family reunion. If a gardener sticks with top dressing the lawn using well-decomposed compost at least once a year, good things happen."