Lowering (or raising) pH is more complicated than a simply #'s/acre ratio. The amount depends on soil type. If you have a very sandy soil it will take less. If you have a very high organic content it will take more.

Sulfur will lower pH. Get it with iron or aluminum (iron or aluminum sulfide).

I don't know what it costs in TX to get a complete soil analysis, but I doubt it's more than $15-$20 per sample. Scrape away ground cover and scoop soil from the surface down to about 6-8 inches. Mix it thoroughly in a plastic bag. Put a plastic label inside the bag and also label the baggie (or box) that you package the soil in. Call your local NRCS office (blue pages in phone book) and get the address to send the soil.

Here's a link: http://aggie-horticulture.tamu.edu/county/smith/tips/land/soilTest.html