Put them in the ground and they likely will be dead in a year. You can only grow blueberries in the southwest in containers where you can control the soil pH. Trying to control pH in alkaline soils would be a huge amount of continual work.

You seem to indicate you successfully grow them in Tucson for two years so what do I know, but then why are you asking anyone's advice since you literally are the expert? If your routine is working why fix it?

I only know of aluminum and certain nitrous compounds to be avoided with blueberry plants.

I think the best thing for them would be to keep them in their containers. I've started using drip systems this year and mine are actually growing. The one I use for my blueberry plants is a pump that pumps rainwater from a 5 gallon bucket into the containers. I just refill the bucket every 2-3 weeks with rain water from my "rain barrels". It's about 30 bucks on amazon, and I change the 4 AA batteries it uses about 3 times a year. Here's a link to it. By the way, if anyone knows of a watering system like that one, but is plugged into an outlet, let me know.

For 2 years I tried acidic water to make up for the alkaline soil I was using and my blueberries died each year. This year I just went to pure peat moss; they look so much healthier. Granted a dead plant isn't hard to look healthier than, they actually look like plants now. I just use pure peat moss because I don't want perlite causing extra drainage on the already fast draining peat moss.

Blueberries need a soil pH of 4.0 to 5.5. Our tap water has a pH of 7.5 so watering with this water will drive the soil pH up quickly. The only way to maintain the soil pH is to water with low pH water. The pH of rain water is around 5.0 to 5.5. Using rain water is probably all you need for blueberries to be healthy. You could add a little acid to the 5 gallon bucket if you feel the soil pH needs to be lower. I use 85% phosphoric acid so very little is needed, for me it is 3ml in 5 gallons of tap water every two weeks. I chose phosphoric acid because plants need phosphorus. You could use other acids too like sulfuric or citric.

The manufacture of a sanitizer I use at work stated that their product is not only environmentally friendly it is actually good for plants as it lowers the PH of the soil. The guys growing grapes down the road told me they inject acid into their watering systems to control pH. That is how I got the idea to use acid in the water. It has worked very well for my blueberries so far.

My question restated is - is a build up of phosphorus something to be concerned about? If it is then using a fertilizer that does not contain any phosphorus would be a good idea. Maybe changing the type of acid every once in a while too.

I'm always hearing about people worried about the phosphorus leaching out of their containers/ground and wondering how frequently they need to reapply it. I could be wrong, but considering how little you're using, I would put phosphorus buildup pretty low on my list of worries about blueberries here in southern AZ.

Let us know if you find a way to grow them in the soil, I would be very interested in trying it as well, although I'm pretty sure it'll take more than just acidic water, unless your soil is very different from mine.

I shouldn't have mentioned that I put them in containers. Everyone seems to be ignoring that I said they have been in the ground for two years. They have only been in containers for about 2 weeks.

They were in an area where they got early morning and late afternoon shade. I also add a couple scoops of miracle grow in each bucket of water. Just ate a blueberry off them this morning. Fat and juicy but not quite ripe yet.