Interesting poem.

One thing seems clear to me: the "child new born" is not being sacrificed. It must be the youngest incarnation of the same scarecrow figure mentioned in the first two verses at different ages. They all tell the narrator to love them, but s/he suspects that they are not real humans.

Also, I am not sure whether any existing ritual is referred to at all. A scarecrow is obviously a realistic object, but who is the old man? A Guy Fawkes effigy would be burned, not hung / hanged.

As for the dons, they might be symbolic of the twelve months. The passing of the seasons is an old symbol of the sequence of generations and ages. The corn (= wheat, thus yellow enough) seems to grow every year, but lovable human value remains doubtful.

Anyone with better ideas?