Contact herbicides like paraquat and PPO inhibitors like Cobra and Ultra Blazer as well as Storm and Basagran will control weeds more effectively when applied in higher volumes of water that improve coverage of weeds. Slowing down ground speed will also help. These herbicides need to cover as much foliage of the weeds as possible. I understand that there is a lot of ground to cover but these two practices will increase control. Also, apply these herbicides when weeds are small. Larger weeds often have more foliage that is not covered by herbicides and they also have energy reserves in roots that allow regrowth to occur. Obtaining less than complete control tends to move populations towards resistance. Plants that are partially controlled are also capable of producing seed at some point during the season, although development may be delayed.