When testing soil pH, one method, used by soil science labs, is to mix the soil sample with distilled water, and then filter the soil & water mixture. The result, the filtrate, is what gets tested for pH. The test can be done with a calibrated pH meter, or it can be done with dye indicators. For really accurate results, you need a pH meter, because these units can be calibrated so they will indicate plus or minus 0.01 pH unit. So if you need to know that your soil is at 6.45, because 6.46 is too high, then a pH meter is the method of choice. The same filtrate described above can be tested with a dye indicator, and the result might be 6.4, plus or minus 0.2 pH unit. That means the sample has pH in the range 6.2 to 6.6, and this is close enough for some gardeners.

In my soil testing laboratory in graduate school back in the 1960's we allowed the water and soil mixture to sit for 30 days before testing when we were doing serious work. I once attempted to explain to someone that it is indeed the pH of the "soil solution" that is important but amature horticulturist just don't get it. NASA has a site on soil for some reason and they start by explaining that it is the ph of the soil solution that we really want to test; but then on the 'how to' page they revert to the language of testing the 'soil pH' and don't even mention soil solution again. (pH is pritty complicated as you must have figured if you have done any serious acquarium stuff.)

The closest large seller of farm fertilizer is about 50 mi south of here, but I can arrange a stop there on my way to getting pastured meat in the Fall. There used to be one not 15 miles from here but no more. As some of you know, my pH=9.2 water coupled with pH=7.7 soil can be a handful. Only grapes need it in the orchard, and I give it to tomatoes and potatoes in the garden, and of course I add more organic matter than most (21% OM in the garden). Anyhow, IIRC in late 2011 one 50lb bag of sulfur was $20. I had to sign a declaration that it and the rest of the stuff was intended for food production not to pay the sales tax. If you have relatively large holdings, it pays to go to such a place. A single 50 lbs urea bag allows many years of fertilization between trips. The 2011 trip was concomitant to starting the orchard in horrible, lifeless, compacted P=7ppm soil, so I got 25lbs of superP, 100 lbs of sulfur, microminerals solution to be added in the sprayer, and 50lbs of urea which will take me to 2020 or so. I have now added over 30 tons of wood chips to the orchard, and the soil is less horrible, but to start it you have to do a first amending.

Check this doc from, of all places ... the UC Ag Extension program :p http://ceriverside.ucdavis.edu/newsletterfiles/Topics_in_Subtropics10457.pdf They did a comparative test of several commercially available soil test kits, comparing the results to lab tests of the same samples, and actually found a couple kits that provided reasonably reliable results. Recommendations were a kit called "RapidTest", and a kit called "La Motte Soil Test Kit" (get that specific model, they tested another La Motte kit with poor results). RapidTest was slightly more accurate -- but it was only good up to pH 7.5, and gave unreliable results above that. Here is a link that might be useful: Testing Commercial Soil Test Kits