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Thursday, April 19, 2012 03:31 pm

Feeding the soil builds sustainable lawns

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Spraying chemical fertilizers and pesticides on lawns is like giving kids junk food, says landscape designer Cathy Bilow. They’ll be invigorated for a while, but eventually they’ll crash and burn. The chemicals kill organisms in the soil that feed plant roots, and as a result “our lawns are dead,” she told a recent class at Lincoln Land Community College on sustainable lawns and landscapes.

A sustainable lawn is one that thrives with as little inputs and labor as possible. It is better for the environment, not only because it lessens chemicals going in the ground, but it also reduces carbon emissions from mowing and supports bees, butterflies and other wildlife.

Bilow, who works at Grieder Landscaping in Bloomington, where she founded Kid Conscious Lawn Care, says the key to a sustainable lawn is cultivating healthy soil. “When soil is healthy, plants will thrive, and thriving plants are more tolerant of disease and drought,” she said. Instead of killing soil bacteria, insects and earthworms, we should be nourishing them with compost.

One cup of soil contains as many bacteria as people on the planet, she said. Microorganisms have a kind of symbiotic relationship with plants, supplying the nutrients plants need in return for the sugars their roots give off. As bacteria and fungi decompose organic material in the soil, they make nitrogen, phosophorus, potassium and other nutrients available to plants.

One of the easiest ways to feed microbes is to leave mowed grass on the lawn, preferably mulched by your lawnmower to decompose faster. It saves the labor of raking and bagging, and grass clippings alone can supply a quarter of the nitrogen needs of a lawn, according to Bilow. Leaves can also be chopped up with the lawnmower and left on the lawn or placed around trees and perennials.

The first thing Bilow recommends for transitioning to a sustainable lawn is to start a compost pile with leaves, weeds and other organic debris from lawn and garden. A cubic yard of compost applied annually is all that is needed to fertilize a thousand square feet of soil. Food scraps and horse or cow manure can also go into the pile, but she advises against using too many lawn clippings because they can make it slimy and anaerobic, taking longer to decompose.

Bilow, who is accredited in organic land care from the Northeast Organic Farming Association, also endorses humic acid, liquid fish, seaweed, corn sugar and molasses as good organic fertilizers for the soil.

Weeds will begin to move out on their own once the soil is vibrant enough to support lush growth. Dandelions, like most weeds, are opportunists that take advantage of weaknesses or bare spots in a lawn. “If you give them an inch, they’ll take a mile,” said Bilow. A lawn with a lot of dandelions indicates a soil deficient in calcium, and she recommends composted leaves as a remedy for it. Other weeds can indicate that your soil is compacted or infertile or that your lawn is improperly mowed or watered. Grass should be mowed at the highest setting to discourage weeds, and there should be enough room in the soil to permit the flow of air and water.

Bare spots or trouble spots in the lawn can be replaced with plants native to Illinois to reduce mowing, watering and weeding. Native plants have deeper, sturdier roots than grass, and since they grow taller, they keep weeds down. Clover, which people actually planted in lawns before World War II, is a native plant that is low-growing, drought-tolerant, and makes its own nitrogen. Bilow says it is making a comeback, and a Chicago company is now growing clover sod.

 In designing a sustainable landscape, the goal is to replace as much lawn as possible with native plantings. To convert an area, Bilow removes sod around the perimeter, and then lays down cardboard over the grass interior. She spreads about a foot of soil and compost on top of the cardboard, which serves as a weed barrier, and installs plants whose roots grow through the decomposing cardboard. Alternatively, carpet remnants can be laid down to kill and compost the grass. After they are removed in a few months, the bed is ready for planting.

Bilow suggests adding a rain garden to the landscape to manage water flow and prevent soil erosion. A trench filled with rock directs rainwater away from the house and toward plants in the garden. By passing through more soil, the water is filtered before it enters the groundwater.

Homeowners who embark upon a sustainable landscape, Bilow stresses, have to change their expectations of what a lawn is. “We want a miracle that is going to make our lawns look like Augusta National, but that’s not going to happen.”

They also should be aware that eliminating chemicals means more labor. “There isn’t anything that’s going to take care of itself,” she said. “Sustainable means lower inputs, but not no inputs.” She doesn’t rule out the occasional spot spraying of individual plants, but opposes the wholesale spraying of lawns that is common practice today. “There’s too much misuse and overuse of synthetic fertilizers and pesticides.”

Karen Fitzgerald of Pleasant Plains is a writer with a master’s degree in science and environmental reporting from New York University. She can be reached at kmfitz3@juno.com.

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