Achieving such yields in a test garden does not mean they are feasible for urban farmers in the Bay Area. Most urban farmers in California lack ecological horticultural skills. They do not always optimize crop density or diversity, and the University of California’s extension program lacks the capacity to provide agroecological training.
The biggest challenge is access to land. University of California researchers estimate that over 79 percent of the state’s urban farmers do not own the property that they farm. Another issue is that water is frequently unaffordable. Cities could address this by providing water at discount rates for urban farmers, with a requirement that they use efficient irrigation practices.
In the Bay Area and elsewhere, most obstacles to scaling up urban agriculture are political, not technical. In 2014 California enacted AB511, which set out mechanisms for cities to establish urban agriculture incentive zones, but did not address land access.
One solution would be for cities to make vacant and unused public land available for urban farming under low-fee multiyear leases. Or they could follow the example of Rosario, Argentina, where 1,800 residents practice horticulture on about 175 acres of land. Some of this land is private, but property owners receive tax breaks for making it available for agriculture.