ploughland vs fallow

ploughland and fallow both are nouns.

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

As nouns, fallow is a hyponym of ploughland; that is, fallow is a word with a more specific, narrower meaning than ploughland:

ploughland: arable land that is worked by plowing and sowing and raising crops
fallow: cultivated land that is not seeded for one or more growing seasons

ploughland (noun)	fallow (noun)
arable land that is worked by plowing and sowing and raising crops	cultivated land that is not seeded for one or more growing seasons

ploughland (adjective)	fallow (adjective)
	undeveloped but potentially useful
	left unplowed and unseeded during a growing season