muddy up vs soil

muddy up is not a noun while soil is a noun.

Word	Noun	Adjective	Verb	Adverb
muddy up	No	No	Yes	No
soil	Yes	No	Yes	No

As verbs, soil is a hypernym of muddy up; that is, soil is a word with a broader meaning than muddy up:

Other hypernyms of muddy up include begrime, bemire, colly, dirty, grime.

muddy up (noun)	soil (noun)
	the geographical area under the jurisdiction of a sovereign state
	material in the top layer of the surface of the earth in which plants can grow (especially with reference to its quality or use)
	anything regarded as making something unclean
	the part of the earth's surface consisting of humus and disintegrated rock

muddy up (verb)	soil (verb)
dirty with mud	make soiled, filthy, or dirty