Good question... all I know about growing rice is the horror stories my mom has from china when they went to the field as part of their "re-education"... It mostly involved stepping on weeds into the dirt and puling off leaches as you went.
My Indian co-workers say, it's best to do an aquaculture system where you put freshwater fish in the rice paddy. The fish will help keep down weeds, worms, bugs, etc. Freshwater shrimp are another option.
Leeches unfortunately are a real concern. I am too squeamish about vampiric critters to do this myself.