Yes, it's very possible. In fact, around here, it's not that uncommon to see our clay soils under 4.0. It may be worth getting a test done at a soil lab for confirmation.

Thanks stompede, so what can I do to correct chlorosis on my trees. I was going to apply sulfur, but that will only make the soil more acidic?

osprey

You should consider seeking advice from the NMSU coperative extension office for your county--folks there should be familiar with the soils in your area and the needs of the trees that you have.

Here is a link that might be useful: New Mexico State Univ. county extension offices

Osprey

Yes, there is nothing inherent about clay preventing its' having low pH. Never the less, I'm a bit surprised at your findings. Are you certain the pH reading was accurate? I'm only going by intuition here, with the dry areas tending towards alkalinity. If this is in fact the correct pH, than sulfur will make it worse. You would want to use lime to "sweeten" the soil. But again, I'm surprised that this would be necessary where you are.

+oM

If you had a complete soil test done by a lab, then I would believe the pH number - if you used a home test, I would be skeptical, as those these tests are usually inaccurate as far as absolute numbers go. In other words, you can use one, and keep using it, to see how the pH of your soil alters over time, but the number you are getting may not be right, even though it will accurately reflect the changes. Sorry, this isn't coming out the way I want it to, so I hope I'm not confusing you....