From Inside Urban Green:
"Most community garden raised beds I have seen are a bad joke. When you can see the insides of the boards and that the grade level inside and outside the bed is about the same it’s more accurate to call them flat beds, or faux beds.
For one thing, these so-called raised beds lack oxygen because of soil compaction or they were never filled to begin with. No wonder the plants are weak looking.
They also lack protection against lead contamination from the city soil below. I would not eat vegetables from most city gardens that I have seen.
Have any of them heard of sub-irrigated planters (SIPs) that supply both water and oxygen online, are easy to use, save precious water and help protect the environment from nitrogen and other pollutant runoff?
SIPs have the potential to be disruptive technology, even though they date back more than a hundred years. With help from a large well-respected corporation they can become the cell phones of urban greenscaping."
Inside Urban Green: Larry Page on the Google Sidewalk Labs Announcement http://buff.ly/1efjUml