There are two basic types of lime used for growing plants, they are calcitic and dolomitic.
Dolomitic lime is the source most commonly used in North Carolina.
By law, dolomitic lime must contain at least 6 percent magnesium. In most cases, if magnesium is low in the soil and the pH needs to be raised, dolomitic lime is recommended as the source because it will usually provide the necessary amount of magnesium. If, however, the pH is at the right level or too high, you will need to use a magnesium fertilizer to provide the proper amount of magnesium. Never apply dolomitic lime solely for the purposes of supplying magnesium. Also, if you choose to use a calcitic source and you need magnesium, you will need to use a magnesium fertilizer.