I remember learning in school that some of the most profitable cash crops early on in the southern colonies were tobacco, indigo, and rice. Tobacco and indigo seem to make sense, but why was rice, a food crop, so profitable that it required large plantations worked by slaves?
There was quite a lot of early experimentation with possible crops in the new colonies, and rice seems to have arrived around 1685. Rice is a warm-weather crop, and plantations growing it thus did not compete with English farmers. It is labor-intensive and land-intensive (corn is far more productive per acre) and it's not surprising that it would be a plantation crop where labor was cheap and land plentiful. But an important factor was the slaves: they already knew something about how to grow it- they'd done so in Africa- and so the plantation owners could make use of their expertise.... even if they didn't reward it.