soil vs muddy up

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

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

As verbs, muddy up is a hyponym of soil; that is, muddy up is a word with a more specific, narrower meaning than soil:

Other hyponyms of soil include foul, contaminate, foul, pollute, smear, slime, muddy, splash, mire, muck, muck up, mud, crock, blemish, spot.

soil (noun)	muddy up (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

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