What are Mama and Papa doing that could make them lose their land?

Big Ma signs the land over to her two sons so that it cannot be taken from them after her death and so that it will require both of their signatures to sell it. Mr. Jamison agrees to put up the credit for a group of black families to shop in Vicksburg and says that not all white Southerners feel the same way as the Grangers. Nonetheless, he reminds the Logans that the Wallace store is on Granger land and that Harland Granger lives in the past. Also, starting a boycott against the Wallace store is tantamount to saying that blacks and whites are equal by seeking to punish the Wallaces for the murder of a black man, a claim that may be dangerous in their town's current racial climate. Even if he cannot beat Granger or the Wallaces, Papa says that he wants his children to know he tried.

A few days later, after taking orders from the other families, Papa and Uncle Hammer take the wagon to Vicksburg to buy goods at the store there. The day after they get back, Mr. Granger arrives at the house. He suggests that their loan for the second two hundred acres of land might come due anytime, especially since the bank owner doesn't like people stirring up bad feelings in the community. He adds that he might have to charge his sharecroppers more than their usual portion of cotton that year, so they might not be able to pay their debts. Granger leaves after saying he plans to get the land back and that there are a lot of ways of stopping David Logan. Papa says he better make them good.