After seeing these things, I became interested in rice growing. Some of the terraces are that old. The wet rice method is very advanced. It requires flooding the field and then changing the water level regularly until harvest time, when the water is drained and the field is allowed to dry. There are at least two advantages of wet rice over dry rice farming.
Wet rice produces two crops a years instead of one.
And wet rice is ecologically neutral. The same ground can continue to produce wet rice forever. It does not lose nutrients. Other methods require crop rotation or other ways to keep a field fertile. The trouble or perhaps additional benefit of wet rice is that it requires a division of labor.