Urban agriculture may solve issues of feeding urban populations. It has been estimated that the total rooftop space in China is about 1
million hectares, some of which can be converted for rooftop farming. This article present here a feasibility study of hydroponically grown vegetables
in a rooftop screen house in Guangzhou, China. None
of the roof hydroponic vegetables exceeded the maximum residue limit
for lead, arsenic, cadmium, chromium, mercury, or nitrate. In contrast, 5
of 98 market vegetables were contaminated by exceeding the maximum
residue limit for lead. Similarly 3 were contaminated for arsenic, 23
for nitrate, and 2 for organophosphate or carbamate insecticide.
Compared to high-end vegetables sold on the market, rooftop-grown
vegetables were competitive in cost and quality. Given that many
countries have limited arable land to feed a large population, the
widespread adoption of rooftop hydroponics could help expand the total
area available for food production.