If the soil is too heavy, you can improve it by mixing in quality compost and gypsum. If the soil is too acidic, add lime to achieve the preferred pH. Soil's pH Levels For optimal growth and fruit ...
If the soil pH isn’t quite right, I’ll look to adjust it. To do this, I simply mix in some sulfur or ericaceous compost to make the soil more acidic. To make the soil more alkaline, mix in some lime.