Why were many african american farmers caught in a condition of debt peonage ?

Peonage is something of a system that the employee is made to pay back the debt to the employer with work and this is also considered as debt slavery. many African American farmers caught in this situation because they do not have enough money to pay for goods from the stores. This situation happened during the reconstruction period after the civil war. Since they cannot afford land they cultivated crops in other's land and share the crop.