There's a better way to do it.. Trees can be planted in deserts without irrigation using technology developed by a Dutch company called Groasis [0]. They have also recently come up with a new version of their Waterboxx that can use any kind of wastewater to plant trees, even sea water. [1] Looks like it works via solar condensation which then wicks into the soil so the roots can follow it down to the deeper capillary water ~3 meters below. So no need for drip irrigation.
This new water filter box will come in handy for ongoing restoration projects in the Galapagos Islands etc where fresh water is unavailable. Will make a post for it when more information becomes available.