Do you suppose this has anything to do with a certain commonly used phrase

When I was in the military, I was on the island of Malta to pick up some aircraft parts. The British treated me extremely well as they always do and invited me to eat dinner with them. Malta is mostly a desert island with little of no greenery anywhere. The Brits served me some delicious little grape tomatoes. Being a carrier pilot and mostly at sea, this was a real treat. I asked them where they got the tomatoes and was told they raised them on the island. I was puzzled realizing there is little or no plant life there and asked how they did that. They told me the locals dig a hole, crap in it and drop in the tomato seeds. I spit up tomatoes all over everyone at the table! True Story

That would tend to curb one's appetite in a hurry

Increasingly I see both canned and frozen food from China for sale, and yet I cannot dispel the vision of "night-soil"

There are some things that one just should not think about

Gardener's call it "Liquid Gold".

Very apt description