when you got talking about 'drilling' a smallish diameter hole down into a bedrock pocket to make a wicking ribbon that you could then plant a tree on it got me thinking.... I'm planing on jetting a well in yard soon, and to do that the easy way you take a 2" diameter PVC pipe and hook a hose to one end and cut teeth into the other end. Turn the hose on and start digging (the teeth loosen the soil and the water transports it to the surface (around the pipe)). Now of course in the desert there isnt a lot water so one could use air instead with some modifications to pipe diameters to ensure that the sand would semi reliably create a complete meniscus allowing the air to create a bubble and push the sand to the surface. Once you have the PVC pipe down to the bedrock, you would fill it with your organic matter and then remove the pipe, leaving a 2" diameter wicking column.
Paul / Owen if this sounds like some thing that you want to pursue let me know and I'll work on the details and get model made.
Yeah... I dont know why I got moved here. I posted it on what I thought was the show discussion for the 'greening the Sahara' podcast episode. If you or anyone knows how to get it back there please let me know what to do. I was attempting to offer Paul / Owen my abilities in developing a method of digging a long narrow hole, to accomplish what Paul was talking about in his podcast.
I didn't hear the podcast but I am downloading it now. The idea is intriguing.
I have watched videos of jetting a well, and if I recall correctly it has a depth limit of 10-12 feet, probably determined by the volume and velocity of the water. I am curious what type of organic matter would be used for the wicking. I am thinking of a mix of sterilized compost and sawdust. Sterilized so you don't introduce bacteria to the water table. In my theory the tree would send down a taproot/feeder root through the most fertile substance and when that food was exhausted it would send out feeder roots through the normal topsoil zone resulting in a drought tolerant deep taprooted tree.
The Greenhouse of the Future ebook by Francis Gendron