Question

What push factors drove farmers to give up their farms and move to the city

Answer 1

 Lack of Jobs/Poverty: Economic factors provide the main motivation behind migration.

Answer 2

They had to produce more and more crops to raise enough money to feed their families. Over time the money was cut down because of how much they produced. Kind of like clearance. They couldn't feed there families anymore so they sold or gave their farm away and moved to the city for better work