This probably isn't much help but most slug/snail bait pellets contain iron phosphate, maybe an occasional application would help add some iron to the soil?

Thanks. That makes some sense, but it is well understood that phosphates just tend to aggravate iron chlorosis. So iron phosphate probably isn't a good way to treat chlorosis. This isn't about chemistry, evidently. The nucleus’ ability to regulate gene expression in response to low iron is interfered with by phosphorus. So phosphorus is an important nutrient, BUT it's not handy if you have iron chlorosis.

I just heard back from Southern Ag. Very interesting. Their "Liquid Iron" is chelated with Lignin Sulfonate. They say that this chelation isn't very stable in alkaline soil, as noted above. The stuff is a mild acidifier, but probably not enough. So they say that I either have to aggressively acidify (which, as I said, is not very credible for me), or else do foliar application. That's a bit more trouble, but foliar application doesn't depend at all on the soil pH. Good idea!

FWIW, many treatments, including Ironite, just have a hefty dose of sulfur to try to acidify, in order to preserve the plant-usable iron.

Treating iron chlorosis can be somewhat tricky, I guess.

Have you tried using soil sulfur to bring down the pH? (Oops - just saw that suggestions at the end of the comment above.) We use it when growing blueberries in southern Ca.

As I said, acidification of my soil is sort of a losing proposition because of my high pH irrigation water. I irrigate like crazy in the summer, so applied sulfur goes "down the drain" pretty fast. But yes, it may be that amending soil with sulfur is simply what you have to do to make any iron amendment last.