I would recomend mowing (if you can - atv mower?) the weeds early and often and not let the weeds go to seed. Use the plow or a harrow scratch the field to open the soil. I would plant straight clover (ladino and red). This is a low cost/simple approach. You could get more elaborate by spraying, no-tilling, etc, but this might be a low risk way to start.

ps - make sure to take a soil sample first