How do you control weeds in an annual pasture?

Question: I want to plant annuals for grazing on 10 acres of established pastureland. We are looking at sorghum-susan grass, and maybe grazing corn. We have tried to do this a couple of times in the past using a no-till drill in existing pastures. Even when we mowed the pastures quite low, the annuals did read more How do you control weeds in an annual pasture?