There are several problems in looking for mention of land or real property in wills. Any land which had been inherited by the owner was "land of heirship" or "property of inheritance" until the Wills Act was passed in 1869. So only after 1869 can you expect to find reference to all land owned by a testator. Before this many landowners adopted wheezes such as sales in trust, or sale and re-sale so they could control what happened to their property.

If they did not take these steps the heir would inherit most of the land.