Tobacco farming dramatically changed Southern Maryland's natural environment by depleting rich soils of nutrients. In the 18th and 19th centuries, farmers rotated fields, introduced fertilizers and guano (bat dung), and employed deeper plowing methods to maintain production levels, and all of these activities taxed the environment. The laborious, 14 month farming cycle also impacted the social and racial landscapes. Beginning in the late 17th century, plantation owners turned to African slaves to work the money crop. Transported across the Atlantic Ocean in deplorable conditions, these slaves were housed in spartan cabins in the colonies. Sotterley's lone surviving slave cabin dates from c. 1850.