Vinegar can be used as a natural weed killer, but it may also harm St. Augustine grass if applied in high concentrations. It is best to use vinegar carefully and in moderation to avoid damaging the grass.
There is not really any weed control out there that will kill one type of grass and not the other. If you want to get rid of Bahia grass in St. Augustine, you best bet is to spray the areas of Bahia grass with Roundup (the ready to use kind with the blue sprayer). Avoid as much of the St. Augustine as you can as Roundup is non selective, and then in the bare areas left by the dead Bahia grass you can put new St. Augustine in 7 days later. If the bare areas left are not too large, you can fertilize the St. Augustine encouraging it to spread into the bare areas.
St. Augustine
In St. Augustine grass it is most important to apply a crabgrass preventer and fertilizer in early Spring. Far easier to prevent than to kill later as almost anything that kills crabgrass can kill St. Augustine grass. Our Ace Hardware sells a crabgrass preventer in the Spring. They now have a product called Garden Weasel Crabgrass killer. A container of this powder will do up to 200 sq. ft. Must be applied to wet leaves on the crabgrass. I found I did a second application on some "tough guys" but it worked fine.
It looks a lot like st Augustine grass, but the blades are a little smaller.
nitrogen
Probably St Augustine of Hippo because it invades everywhere and chokes out anything in it's path.. Amen - lol
Yes, the city is named for St. Augustine of Hippo.
Saint Augustine grass and Bermuda grass can coexist but there will be issues. Saint Augustine grass needs less fertilizer and usually grows faster. So it could make mowing the grass a frequent chore.
The St John's County/St Augustine Airport is located about 8 miles from St Augustine Beach.
In terms of water, it's the other way around. St. Augustine grass is less drought-tolerant than Bermuda grass; it grows best in tropical climates where there's lots of moisture (swamps, shorelines, etc.)
In south texas, lawns are generally Bermuda, St Augustine, or the more expensive Zoysia
St. Monica is the mother of St. Augustine.