Why does methane come out of rice paddies? Does it come out of corn fields and other stuff, too?

Answer 1

Methane comes out of lots of things... In rice paddies it is likely being generated from the breakdown of startch by methogenic bacteria living in the soil.

Methane production seems to be increased by human activity, probably because we stir soil up when we farm making food available to certain soil bacteria that would otherwise not have access to it.