btw... I just did a bit of research on using sulfur and came up with an article that makes things pretty clear (at least to me)... it says, in part:
"Elemental sulfur and aluminum sulfate are the most common amendments used to decrease the soil pH. Elemental sulfur is the safest option to decrease soil pH; it is relatively inexpensive and available via local agriculture suppliers and garden centers. Unfortunately, it is slow to react. Elemental sulfur must go through two processes, a biological process and a chemical process, before soil pH is decreased. This often takes 3 to 6 months of warm soil temperatures when soil biology is active. Aluminum sulfate reacts in the soil very quickly as it must only undergo a chemical process. The change in pH happens within days or weeks. However, aluminum sulfate is not an ideal amendment because requires more material than elemental sulfur to reduce the soil pH and aluminum is toxic to plants."