piece of ground vs piece of land

piece of ground and piece of land both are nouns.

Word	Noun	Adjective	Verb	Adverb
piece of ground	Yes	No	No	No
piece of land	Yes	No	No	No

As nouns, piece of ground and piece of land are synonyms defined as:

Other synonyms of piece of ground include parcel, parcel of land, tract.

piece of ground (noun)	piece of land (noun)
an extended area of land	an extended area of land