Lime

Lime is commonly applied to soil to improve fertility and to reduce soil acidity. The application of lime reduces the toxic concentrations of the elements aluminium and manganese. It supplies calcium and increases the availability of some nutrients such as magnesium and molybdenum. The application of lime will improve soil structure and release nutrients locked up in the soil.
Gypsum
Gypsum is added to soils to break down the clay.  As the gypsum dissolves it acts as a flocculating agent on the finer soil particles which form crumbs so that the soil becomes better aerated and has greater water holding capacity.This will improve the soil structure.
Dolomite Lime
When limestone has high magnesium content it is called Dolomite or Dolomitic Limestone. Dolomite is generally defined as having a minimum magnesium carbonate content of 28% and a minimum calcium carbonate content of 35%. Dolomite Lime is suitable for areas extremely low in Lime.