hey, paul
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.