The sentence that expresses the main idea is
1. (1)In the South, the Civil War destroyed half the region’s farm equipment and killed one-third of its draft animals. (2)The death of slavery also ended the plantation system. (3)The number of farms doubled from 1860 to 1880, but the number of landowners remained the same. (4)The size of the average farm dropped by more than half, as sharecropping and tenancy rose. (5)A shortage of cash forced Southern farmers to borrow against future crops. (6)Crop liens and high credit costs kept a lot of black and white farmers trapped in a cycle of debit and poverty. (7)So at the very time the rest of the economy was consolidating after the Civil War, Southern agriculture was marching off in the opposite, less efficient direction.