Nice myth for you to believe, but no,they didn't know that then and would not have believed it had you told them. In fact, mechanization of cotton harvesting didn't become practicable until the 1950s. Before that, virtually all cotton was picked by hand.
I first visited Georgia in the early 1960s and there were still plenty of 'share croppers', white and black and still plenty of cotton picked by hand.
No one in the south in 1860 envisioned bringing in a cotton crop without slave labor.
A lot of the crops in Georgia are still picked by hand but we don’t have slaves doing it. Slaves were not doing it in the 60’s either.
There was a lot of other industry that began to be developed in the South in the 1800’s textile mills being a large Southern industry.