Not the one at the back that's fully flooded. We're not there yet! The one at the front that has sprouted black plastic. It's called aze-sheet. Aze is the name of the ridges between the rice paddies.
The sheet is there to add to the waterproof-ness (waterproofability?) of the aze. Our aze are so thick/ wide that it really isn't an issue but as the field hasn't been used as a rice field for about 40 years we don't know if it is riddled with mole and mouse holes or whatever so it's like aze insurance.
Aze sheet close-up. Oh and if you look really closely you can see that the field to the South (the downhill side) is also using aze sheet. And that's another great reason to use it- the neighbours do. And they recommend we do, too. Strongly recommend it. And sometimes farming is more about people than plants... that's just the way it goes.