unbroken vs fallow

unbroken is not a noun while fallow is a noun.

Word	Noun	Adjective	Verb	Adverb
unbroken	No	Yes	No	No
fallow	Yes	Yes	No	No

unbroken (noun)	fallow (noun)
	cultivated land that is not seeded for one or more growing seasons

unbroken (adjective)	fallow (adjective)
not broken; whole and intact; in one piece	undeveloped but potentially useful
marked by continuous or uninterrupted extension in space or time or sequence	left unplowed and unseeded during a growing season
(especially of promises or contracts) not violated or disregarded
(of farmland) not plowed
not subdued or trained for service or use