How did farming practices in the midwest during the great depression contribute to the conditions which caused the dust bowl? a. farmers left their fields unplanted because they had no money to buy seeds, leaving the ground uncovered. b. farmers dug extensive wells to irrigate crops and drained underground water supplies, which dried out the soil. c. farmers switched from growing wheat to raising livestock and overgrazed the land, destroying the native plant species. d. farmers plowed deep into the ground to create fields, destroying existing root structures that held the top soil together.