Combining some advice from Robert Kourik - Lasy Ass Gardening book and my local Master Gardener, I put together this system:
First to place the lines, I asked my landscaper to rent a ditch witch to dig the trench.
This is expensive, but hopefully this will be trouble free and last a long time.
While trenching is expensive, PVC pipe is pretty cheap. While my Master Gardener said to put in as much PVC pipe as possible, my landscaper recommended to limit the PVC pipe to a max of 4 - he said anymore and it gets to difficult to fix a leak.
I installed two 1 1/4" PVC lines in the pipe with tees going to risers every 14'. Either line should have plenty of pressure for the 20 risers I ran on each line.
By having a double system I can have two watering schedules. For example I could have mature trees being watered deeply every few days, while young sapling could be on a short, daily schedule. Simply connect the drip irrigation line to the right pipe. My Master Gardener also recommended a tee value at each tree. This would allow me turn off the water to spot if the tree dies or something else. I am just adding these as I add trees.
For my drip irrigation I am using an in-line drip emitter. Robert recommends 12" spacing. As you can see from the photo, i used way more than I needed for a small tree and the timer only goes on for a few minutes a day.
But there is a method to the madness. First notice the drip line is not just where the roots are, but also where I want them to GO. As the tree grows and the roots extend, I can simply widen the drip spiral and lengthen the time on the timer until it gets to a 12" x 12" spacing. It will take years before I need to worry about adding to or replacing these emitters.
Next I connected my system to a irrigation valve and timer. My old-school landscaper wanted me to get an old-school timer, but I opted for an intelligent Rachio system instead. By linking in to local weather it can calculate tree evapotranspiration and give it the water it needs. It will even delay watering if rain is forecasted. It took some time to get the time right (only 15 minutes with all the emitter line and very clay based soil), but since then the only issue I have had is a valve being stuck open from a pebble in the water line.
For the pies de resistance, I added two outlets where I planted my citrus trees. This will allow me to give the trees a little heat with old Christmas tree lights in the winter if it falls below freezing for a few days. But wire is expensive, so I just set it up to hit 4-6 trees close to the house.
Finally, we planted the tress with a gopher mesh to protect the roots and more wire mesh to protect the leaves from goats and deer. Then it was topped off with a nice coating of wood chips.
I set up spots for 20 trees, but only got 5 in the ground. That's OK, I am all set to go this spring.