A paper published this past July the journal Agronomy for Sustainable Development reports that growing leafy greens in rooftop hydroponic systems can not only produce a steady supply of vegetables—it can also be cheaper than buying store-bought alternatives. [...]
Rooftop farming could also create jobs and reduce the carbon footprint of transporting foods into cities, says Wanquing Zhou, a research associate at the Worldwatch Institute. Those are essential side effects, considering the rapid urbanization currently underway in China: By 2020, Guangzhou’s population is expected to nearly double from 9.62 million in 2010 to 15.17 million—almost equivalent to adding the entire population of New York City. [...]
For the two-year study, researchers constructed a “screenhouse”—a semi-enclosed structure with a roof—on top of a two-story building inside the South China Botanical Garden. Surrounded by screens to ward off armies of insects that thrive in Guangzhou’s summer subtropical climate, 14 hydroponic tanks inside the screen house nursed and fed a forest of seven different greens, including caraway, potherb mustard, and Italian lettuce. The crops were then rotated based on their natural growing seasons—from November through March, bouquets of crown daisy and Italian lettuce populated the screenhouse, while summer and fall months brought waves of leaf mustard. [...]
The team also tested two greens and found that they contained fewer contaminants than their market counterparts—including pesticides, nitrate, lead and arsenic. If the finding holds up for the other five vegetables, the hydroponic screenhouse model could be particularly relevant for urban farming. New York, Philadelphia, Detroit and Shanghai have all had traces of lead contamination pop up in their urban soils.
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