Jefferson raised tobacco for sale to European markets until the early 1790s. Then, market forces and an interest in agricultural reform led him to institute a more diversified operation, with wheat as the main crop. The new system involved a greater variety of tasks, which gave enslaved workers additional skills and increased autonomy, enabling them to negotiate small improvements in conditions for their families.
The cultivation of grain required permanent, plowed fields, and plowing entailed the removal of stumps and a schedule of manuring and crop rotation to maintain soil fertility. Plows needed draft animals to pull them, skilled operators to guide them, and blacksmiths to maintain them. The use of draft animals called for slaves trained in their care. The transportation of grain, fodder, and manure meant wagon-makers and carters. To increase profits, Jefferson erected mills to grind flour, which necessitated carpenters, stone masons, and trained millers.
No longer working lock-step in a gang, now laborers, either alone or in small groups, were dispersed across the plantation, performing a variety of tasks. For the planter, this presented a challenge to efficient supervision; documents attest that Jefferson relied on measurements of the quality and quantity of output—pounds of nails, bushels of flour, yards of cloth—to assess the productivity of his slaves. In addition, the complexity of some of these jobs required specialized expertise and the ability to make independent decisions. The investment in training or purchasing a skilled slave made that person a more expensive, valued, piece of property. Archaeologists currently hypothesize that, under these circumstances, effective slave owners realized the limitations of blunt force and began offering positive incentives to motivate compliance. This development could have given enslaved people some leverage to achieve the marginal improvements in the condition of their lives which is seen in the archaeological record at Monticello.