Surface application of Texas greensand helps the lawn and some plants. Not a quick green-up like foliar sprays. We've been having trouble since the lack of rain of recent years has had us dumping so much alkaline tap water on our yards in its place. Don't know that there is a permanent solution without a return to historic rainfall levels (or changing out the turf/plants), but would be glad to learn of any.

Here is a link that might be useful: Texas greensand

Do you know of any brake shops around you?? they turn drums and rotors that are cast iorn, the cuttings work wonders to green up all plants. I usethem around roses . Allen

My understanding is, with alkaline soils problem is not one of lack of Iron in the ground but one of absorption by the plant. The acid soil makes the Iron present in the soil to an absorbant type. According to my reading, the only way to acidify the soil is to add lots of compost or sulfur. Either can be done only when preparing the ground, before the planting. So, I was wondering if there is a solution after the planting.

Just as with anything else, there are degrees of help for these types of issues. Simply sprinkling agricultural sulfur or other materials around the base of the plant usually does little good but actually working them into the soil two to three inches deep does allow the material to start the process whereby the native alkalinity is slowly changed to a more neutral state. Remember that no matter what you do, it will take some amount of time for the "new" materials to start the change you're looking for so be prepared not to see massive changes in the plants immediately.
Of course, the best option is still to dig in the added materials before you plant but rarely does anyone (including me) think about that beforehand.
Steve

Believe the disadvantage of surface application is not exactly that it does little good, but that it requires both greater quantities of material and more time for same results as applications in the root zone. It's still a decent option for periodically maintaining something like an azalea bed that's already at an abnormally low pH for the area or a lawn that's mildly chlorotic, but not so much for curing chlorosis within the short production cycle of annual veggies.

Our neighbor kept his acid-loving pines looking good with deep iron treatments via root feeder every year or two. Seems it should also work for established crop plants. Am guessing he was using EDDHA chelated Iron because our soil pH sits above 7.... and he was an old east Texas farmer who paid attention those sorts of details.

The MO Botanical Garden page on Iron Chlorosis listed below includes a link to a pin oak treatment using holes bored in the root zone. Might be something that could be adapted on a smaller scale/dosage to other plants.

Other variable that's not been mentioned is the soil's health with respect to the microorganisms that produce acids and siderophores that make ferric iron (and other elements) available to the plants. Don't know if any of the retail "soil inoculants" specifically address chlorosis yet, but may be worth a look. Anyone using these?

A rain barrel/bucket is another thing to consider. Our rain is slightly acidic. But as mentioned before, Dallas tap water is slightly alkaline. Using rainwater as much as possible to irrigate our more sensitive plants is not a total solution, but does seem to help.

Here is a link that might be useful: Iron Chlorosis (MBG)

I second the Green sand option. Heavy apps of that turned my pin oaks from dying to doing very well.

If you scatter soil sulfur granules liberally on the surface and rake them in a bit, they will dissolve slowly into the soil as you water the plants.

Next year, scatter more and dig it in when you prepare the bed.

It's not as dramatic as watering with diluted vinegar, but it lasts longer, and it's an inexpensive solution compared to "greensand"

Vegetables grow very well in our Dallas, alkaline soil, OP. You need to go read a book by our local soil dude, Howard Garrett. It would take me an hour to explain, and I just don't have enough time. Best wishes.
M