I recently heard an interesting pod cast from CBC about SPIN farming.
SPIN stands for small plot intensive farming. Individuals in
Saskatchewan first starting out this venture by renting out peoples'
unused back yard veggie plots to grow intensive crops that they then
turned around and sold. Apparently, they are savvy enough to get
three crops off per year! (An I'm struggling just to get my beans to
germinate...stupid weather). Here's a link to their web site (http://
www.spinfarming.com/), perhaps there's some information there that
might be of interest to other urban farmers.