I live in the Palm Springs, CA. Figuring out the right amount of water for my citrus trees is driving me nuts. I tried a cheap moisture tester, but that didn't help. I can't tell if I'm drying them out or over-watering. As you said I could be losing leaves from over watering or drying them out, I just don't know. Aside from that I notice stunted growth in my healthy trees. Sometimes I think when I am getting it right I will see a little growth, like some new leaves came in on a new tree I tried to rescue from a friend. But then everything stops growing for weeks. I noticed this on all three of my good trees. Is there anything else I can do to try and understand how much to water? Mind you we're at 108 degrees today. And because I'm planting in sand, I think there is no drainage.
What Do I Do if I Have Poor Drainage
Certified GKH Gardening Expert
These trees are naturally adaptive to your climate and are probably served best by a deep watering once a week. Stop worrying and let nature take its course!
Citrus trees in your area will bear all year, but there are periods of dormancy in between when leaf loss is natural. I'd check with a local nursery to see if they can offer any suggestions.