Question

all the cotton the South's most profitable cash crop it was not going everywhere why do some Farmers harvest rice or tobacco instead of cotton

Answer 1

When?

going everywhere?

Answer 2

You can not row cotton profitably everywhere. You need the right soil and water conditions and preferably a large area of flat land.
Rice in particular uses very different soil conditions, like wet.
Virginia climate was very good for tobacco as was Ky and Tenn.

Answer 3

Not all land in the southern states was suitable for the growth of cotton.