I don't know what your instructions were, but what you've said is correct.
The complete subject is "the warm ground."
In the fall, the warm ground melts the first layer of snow.
in the fall- prep. phrase
of snow- " "
ground- subject
melts- action verb
anything else? because i answered this and she said it was wrong
2 answers
all we had to do is find the subject, verb and prep. phrases