Slavery in the United States was nothing compared to the intensity of Cuban slavery where slaves commonly spent as much as 20 hours a day harvesting and processing sugarcane.
Here’s another excerpt from Time on the Cross:
“Cotton was, of course, the single most important crop on large cotton plantations, requiring about 34 percent of the labor time of the slaves. However, the rearing of livestock (including the raising of feed) took nearly as much labor time of slaves – about 25 percent. Corn bound for human consumption took another 6 percent. The remaining 34 percent of the working time of slave hands was divided among land improvement, the construction of fences and buildings, the raising of other crops (oats, rye, wheat, potatoes, etc.), domestic duties, and home manufacturing (especially the production of clothes).”
2/3rds of the time of slaves on Southern cotton plantations was spent on activities which had nothing to do with the cotton crop. The slaves on Virginia tobacco farms had even easier lives.
In terms of the intensity of slavery, sugar > rice > coffee > cotton > tobacco. There was a night and day difference between being a slave on a sugar plantation and a cotton plantation.