Manure in the Bible

Isaiah 25:10 For in this mountain shall the hand of the LORD rest, and Moab shall be trodden down under him, even as straw is trodden down for the dunghill.
Luke 13:8 And he answering said unto him, Lord, let it alone this year also, till I shall dig about it, and dung it:
Luke 14:34-35 Salt is good: but if the salt have lost his savour, wherewith shall it be seasoned? 35 It is neither fit for the land, nor yet for the dunghill; but men cast it out. He that hath ears to hear, let him hear.