Manure like Steve suggests is probably one of the best ways so long as it is
thoroughly decomposed. In any case, you wouldn't use lime to make the soil
more acid. Lime would make it even more basic than you are already. For
quick drops in pH, aluminum sulfate is usually recommended. Powdered sulfur
should drop it over the long run along with the added compost. Manure itself
would help buffer the pH and not really acidify the soil but maybe help
neutralize it on top of the other benefits supplied by the organic material
including moisture retention.
I hope the kids get a good crop.
Gary

"Nicole H" wrote in message
...
I'm in the San Joaquin valley. Our soil tends to be alkaline. Well, at
the elementary school, we have a Life Lab (hands on science w/garden
plots). I have a few teachers who want to grow potatoes.
My gardening book says that pototoes need acidic soil but not to use lime.
How else do I get the soil to move to the acidic side? We're about 7.5 to
8.0.

Thanks
Nicole

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