In much of the eastern United States and Pacific Northwest, soils tend to be naturally acidic. In the prairie-covered Midwest, the soils are close to neutral, and in the drier portions of the West, they're on the alkaline side of the scale. The best way to determine the pH of any soil is to have it tested. Apply the limestone in the fall at the rate of five pounds per 100 square feet for every one point increase in pH. Wood ashes can also be used to raise the soil's pH, and they work faster than limestone. If your soil is too alkaline, apply sulfur.
Elemental sulfur works best, and a granular product is easy to apply.
The application rate for sulfur varies from one to two pounds per 100 square feet, depending on the soil type. If your soil is only slightly acidic or alkaline, just add compost to the soil. Compost has a way of bringing soil pH to near neutral due to its buffering capacity.