What was not a major cash crop in the south

Indigo. Rice, too. Improved answer from Scarlet Ribbons: Indigo had a very brief lifespan as a cash crop in South Carolina. It was introduced to the colony in 1744 and was done and dusted by 1798. Its demise was due to three things - the 1793 invention of the cotton gin that made cotton crops the better investment for lowcountry planters; the latter 18th-century influx of a far superior quality of indigo from India to the world market; and the loss of protective British tariffs and bounties, due to the American Revolution, which lost South Carolina its reliable market for indigo in the dye houses of Great Britain's textile mills and forced the state into an open market competition that it quickly lost.