Buffalograss Turf - To reduce the weed competition, you should prepare your site 1 to 2 weeks before planting and irrigate to get as many weeds up as possible. Then apply Roundup prior to seeding. Currently, mowing is the best method of controlling weeds during the first year of establishment. After the lawn is established, a pre-emerge herbicide such as Balan or Dacthal can be used.
Prairie and Pastures - Planting after the soil temperature gets above 65°F will allow several weeds to germinate before you plant. Then apply Roundup prior planting. After the grass is up 2 inches tall or higher, Ally can be applied for broadleaf weed control. Otherwise, shredding is the best alternative.