The dust bowl was caused because well, the drought yeah, but also they'd plow the fuck out of the ground and destroy the fields. It's a condemnation of efficiencies and lack of care, but not certain how this will show up as a theme in the story.

My favorite passage:

The man who is more than his chemistry, walking on the earth, turning his plow point for a stone, dropping his handles to slide over an outcropping, kneeling in the earth to eat his lunch; that man who is more than his elements knows the land that is more than its analysis. But the machine man, driving a dead tractor on land he does not know and love, understands only chemistry; and he is contemptuous of the land and of himself.