A study by Kathryn Colasanti and Michael Hamm looks at the capacity for self-reliance in fruits and vegetables in Detroit, a city of 835,000 residents and 44,000 vacant properties. Their study compared actual consumption levels to the recommended daily intake of fruits and vegetables. It also considered scenarios for storage and season extension and intensity of production methods (conventional row crops versus bio-intensive). They conclude that about 76 percent of vegetables and 42 percent of fruits could be supplied year-round on ~2,000 acres of land using bio-intensive methods.
Brad Masi, Janet Fiskio, and Md Rumi Shammin, "Urban Agriculture in Rust Belt Cities," Solutions, January-February 2014, Volume 5, Issue 1: p 48