Jap millet is the easiest to grow. Just broadcast and it'll come up. Rice is a little tougher to grow, but if you do, I would suggest raising the water level to just below the top of the stalks after the rice gets about 6 inches tall. That will keep down the weeds in the "impoundment". That said, if you can plant and grow corn in there, do it. Put about 36" between rows which will allow for the ducks to land amongst the corn. If you have ringnecks in the area, you may want to leave an open spot so they can also have a landing spot.