Here in PA we have large worms we call nightcrawlers. Many people say that rototilling kills many worms in your garden bed and I can understand that. But if the rest of your lawn is loaded with worms, couldn't it be possible to just catch them at night and transfer them to the garden bed? In my area, it's very easy to catch 100 plus worms a night. Once you placed them in the bed, it's my opinion that they would enjoy the freshly tilled soil and continue to reside as well as reproduce there.
Rich