When the narrator tells about the wheel barrow, he gives the situation gravity by saying how much relies on this wheel barrow. its not one thing but many things that depend on it.
glazed with rain, giving the audience a sense of it being washed and shiny, however, it gives the reader that color red that is associated with rage, lust, blood and other unclean things, giving the contradiction within the wheel barrow.
Beside the white chickens gives the reader another contradiction, while the red wheel barrow seems to be less clean than the chickens, the animal is associated with cowards and this contradicts the standpoint of purity.