Urban farms differ from rural ones
Sept 2018 — In 1998 the McKinley-Vento Act allowed nonprofit organizations working with disadvantaged populations to use federal land. By 2009 Chicago lawmakers amended city ordinances so that urban farms could exist.
The purpose of urban farms is to provide locally grown produce and sometimes animals for the community. Usually the farms are much smaller than rural ones and the crops are diversified. Sometimes they are so small they can hardly be differentiated from gardens.
These farms grow produce to sell and either provide tax money or benefit the community in another way. Gardens, on the other hand, grow produce primarily for personal use. Restaurant gardens grow produce, sometimes on their rooftops, for their menus while community gardeners either take home their produce or give it away.
Some urban farms are primarily educational, making youth/adults employable; some train future urban farmers and then let them rent incubator farms on the premises. Some are indoor and some are outdoors. Indoor vertical farms use the nontoxic waste of neighbor tenants to feed their produce and then recycle their own waste. Outdoor farms extend their growing season by using hoop houses(covered hoops to protect the plants).
Some urban farms are for-profit and some are not. Some are certified organic by the USDA while others are certified naturally grown by a farm-to-farm organization that requires adherence to the USDA organic criteria minus the exorbitant fee; still others skip both avenues, but adhere to the USDA standards anyway. All revive the soil, which suffered from previous owners; rotate crops; try to avoid chemical pesticides.
Most urban farms grow their produce in soil, but some grow it in water. When the water contains animal waste, the process is aquaponic; when no animal waste is in the water, the process is hydroponic. As with produce grown in soil, the best way to find out the kind of waste used as fertilizer is to ask the growers. Fortunately, this can be face-to-face with local growers.