Asphalt Garden

Urban farms are cropping up in cities across the nation, bringing hyper-local food options and greener streetscapes to areas that once lacked both.
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From GreenSource
Andrea Ward

The New Agrarian Center has a "City Fresh" garden program to turn vacant lots into verdant beds and train residents to grow food for local businesses.

Photos: Brad Masi

Is urban soil fertile enough?

Finding ideal soil conditions for growing vegetables can present a variety of challenges in an urban environment. Previous land uses, especially former industrial sites, gas stations, and drycleaners, can leave soil contaminated with heavy metals or harmful chemical compounds-soil testing is a must. In areas where demolition has occurred, there may be concrete or other inorganic detritus present in soil.

"Most urban lots have what we some times call ‘urbanite,' " explains Brad Masi, executive director of the New Agrarian Center at Oberlin College in northeast Ohio, which leads the City Fresh initiative in nearby Cleveland. "It's a unique urban soil-very compacted and full of rubble." Urban farmers have devised plenty of ways to work with and around urbanite, however. One solution that has caught on in Cleveland and elsewhere is "asphalt gardening"-building raised beds directly on top of unused parking lot space and other paved surfaces. Through workshops hosted by the New Agrarian Center, Cleveland residents learn to fill strawbale- or cinderblock-framed beds with layers of cardboard, wood chips, shredded newspaper and office paper, discarded vegetable matter, and a smaller amount of prepared soil; then earthworms do the job of breaking down the constituents. The paved surfaces function as a reliable barrier between the beds and potential contamination in the soil beneath. "EPA studies looked at asphalt leaching and determined that it doesn't cause any problems with contamination," says Masi.

The availability of cheap and free soil-building elements for Cleveland's asphalt gardens underscores a critical reality that gives cities one small edge over rural areas, at least on this point. "You'll find there's an abundance of material that can be composted," Masi says. "Cities are really rich in that way." Richard Pederson of City Farm in Providence, Rhode Island, (no connection to Chicago's City Farm) makes the rounds of City Farm's downtown neighborhood, collecting leaves from a nearby cemetery and organic waste from area businesses-cups and coffee grounds from a coffee shop, for example. It's a good way to meet the neighbors and introduce them to the farm in their midst, he says. When asked about the fertility of urban areas, Pederson focuses on one number: "Twenty-five-that's the percentage of trash going to the landfill that is biodegradable and could be used to build soil for urban farms and gardens." It's a resource he and others believe could be utilized much more productively.

On the ground techniques

Places like Providence's City Farm show that, given the right approach, it's possible to make market gardens and commercial urban farming operations viable with less space than you might think. Pederson, who was hired at City Farm eight years ago, introduced a variation on the "biointensive" method of farming that allows City Farm to sell vegetables to local restaurants and at three different local farmers markets, while still having leftovers to give to farm volunteers and neighbors-with just 5,000 square feet of their 3/4-acre lot dedicated to vegetable cultivation. Developed in the 1960s, biointensive methods focus on building soil while producing large yields from a relatively small land area. At City Farm this means double-digging the top two feet of soil to alleviate compaction and increase drainage, building permanent rounded beds with walkways to accommodate workers, and planting with particular spacing (depending on the plant), using a hexagonal rather than the more conventional row-based layout. They plant cover crops in the fall, another biointensive element, but unlike strict biointensive farms, which must grow all their soil inputs onsite, Pederson widens his closed-loop soil-building system to include organic material collected from the surrounding neighborhood. "The farm can support local businesses by buying or using these things that would otherwise go to the landfill," he says.

 

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Originally published in GreenSource
Originally published in May 2010

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