I'm a city boy and I have no idea what real farming is like. I only know it can't be the paradise that you see in jigsaw puzzle art and sentimental posters. My guess is that it's hard...so hard that ordinary people do everything they can to escape from it, and they always have.
I seem to remember reading that farming began in the Middle East about 11,000 years ago. My own guess is that it's at least 2 or 3 times older than that. I imagine that a few people practiced it on a very small scale, and only in the most fertile places, for thousands of years. What made a difference 11,000 years ago was...I'm guessing...
...the discovery of liquor! Only getting blasted all day long could make grueling work like that tolerable.
Think about it. Imagine hoeing endless rows of cabbage on a bleak and empty field under the hot sun. The only thing that would make it tolerable is the expectation that eventually you'd reach a jug of liquor that's hidden in a bush at the end of the row.
I'm guessing that once liquor made small scale farming feasible, then slavery was invented to grow little farms into big ones. Slavery probably always existed on a small scale, but liquor-induced farming kicked it up a notch...a big notch!
Did slave owners give their slaves liquor? My guess is that they did. After all, it probably increased productivity. My further guess is that slave owners eventually stopped doing this because liquor addiction was spreading from the slaves to them, the slave owners. 'Just a guess.
Okay, almost everything I've said is conjecture. I've read very little on the subject. You have to admit, though, that it sounds plausible.