I'm slow getting back to this thread, but I so appreciate the discussion! Thanks for further thoughts on sand, grit, crushed granite, etc. Now I know that the sane I bought is builder's sand.
On the alkaline comment, like pollengarden in Pueblo, here in San Antonio we have soil with pH of 8 or 8 point something, as a rule. Plus most yards here sit atop a limestone ledge, which is why I use raised beds.
Now with my own mix of soil (combo of purchased stuff plus my own compost) you'd think pH wouldn't be an issue but I think I'm understanding that even the rain here is alkaline, plus compost made of plants grown in this area (grass, leaves from my yard) will make it more alkaline over time. So no adding lime for me!
Anyway, it's just something to keep an eye on. I read a couple suggestions to add granulated sulphur but I haven't gone down that path yet.
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Soil fix-up
Yes, sulfur is a common acidifier. Sulfur combined with water makes sulfuric acid - handle with care. Protect your eyes and respiratory system from any contact.
It is the Sulfur in onions that makes them keep well - and makes your eyes water. The sulfur in the onion combines with your tears to make weak sulfuric acid. That why mild onions like Walla Walla and Vidalia don't make your eyes water but don't keep worth a darn - they are a naturally low sulfur onion grown in low sulfur soil.
Since the soils here a High in "Free Lime" (available lime), adding acidifier does not help much - the acid dissolves more lime and soil just fizzes until it returns back to near the original pH. Adding organic matter does help, it increases the percentage of non-lime soil. My soil is high in salt, too, so I can't add manure (except perhaps poultry, since they don't eat salt).
I am slowly double digging all my beds, adding organic matter deeply, AND sieving out the little limestone rocks.
To the beds that are directly in the "dirt", I add organic compost that includes pine bark fines, peat, sharp sand, greensand, rock phosphate, azomite (small amount), bone meal, and blood meal. Now it will depend on the area and what I am planting, to add anything else. I did add some manure for my pea beds as well as perlite since these beds have a tendency to compact. This particular area
has been worked several times and is particularly sticky hard clay, but I can see that it has improved a bit.
Sometimes it takes years, unless I just dig out all my dirt and replace it with a soilless mix, which I did for part of my shady bed. It is doing wonderfully and is lush and green with huge leaves.
We live in the forest and lots of tree roots had to be removed for that shady garden. I dug 2 feet down and took all the soil out...including those roots! It took a while, last fall and then spring. I just dug a little at a time, since I am an old lady now.
Rain most places is acidic. Some because of the pollutants in the air from emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. But also as water falls it comes in contact with atmospheric carbon dioxide, or CO2, which is a weak acid and forms carbonic acid.
It is possible for rain to combine with other substances in the atmosphere that will increase the alkalinity of its pH, such as suspended soil dust(which could happen in San Anton), but most rain water ultimately has a pH between five and seven, making it slightly acidic.
If you irrigate, the pH of the water you use will have a huge impact on your gardens soil pH.
Adding sulfur to a calcareous soil is a challenging proposition. Many calcareous soils are highly buffered and it would take alot of sulfur to reduce the pH. I do use sulfur here to treat the soil around my blueberries and have had success. It is stinky though.
Soil is the stuff your plants grow in. Dirt is what you sweep off the floor.