Q: My vegetable garden soil pH shows 7.7. What does that mean and how do I fix it?
A: A vegetable garden soil pH should ideally between 6.0 and 6.5. Your pH is more than 10 times higher than the ideal. There are a few things you can do to help but lowering pH is difficult and most often the change is only temporary. Attached is a publication from the University of Florida which will assist you with specific details on how to raise or lower soil pH.
I am going to provide section from the publication just to be sure what I say is not misrepresented:
The soil pH can be temporarily lowered by adding elemental sulfur. Bacteria in the soil act to change elemental sulfur into sulfuric acid, effectively neutralizing soil alkalinity. However, the effects of elemental sulfur are localized to the area amended and the effect is temporary. Soil pH will begin to rise shortly after soil bacteria exhaust the added sulfur supply. This effect will require repeated applications of sulfur to ensure the soil remains at the desired pH. This is where sulfur addition can get tricky. If too much sulfur is added, or if it is added too frequently, it can actually injure or kill your plants. Therefore, it is important to never apply sulfur in excess of 5 to 10 pounds of sulfur per 1,000 square feet per application. Adding sulfur at high rates or too frequently, can actually result in damage to your plants. If you decide to apply sulfur, make sure to monitor your plants.” http://edis.ifas.ufl.edu/ss480