See:
Site Preparation, Stale Seedbeds, and Directed Nonselective Applications
paraquat (Gramoxone; 2 lb paraquat cation/gal)
Stale seedbeds
Rate 0.50 to 1 lb cation/A (2 to 4 pints/A); use higher rates for heavy weed infestation.
Time Apply just before crop emerges to emerged weeds only. Add a nonionic surfactant or crop oil concentrate as label specifies, taking care to avoid anionic formulations that react in the tank to form insoluble precipitates.
Caution Restricted use pesticide due to acute toxicity. For retail sale to and use only by certified applicators - not to be used by uncertified persons working under the supervision of a certified applicator. Do not ingest or inhale spray mist. Applicators must wear long-sleeve shirt and long pants, shoes plus socks, protective eyewear, chemical-resistant gloves, and a NIOSH-approved particulate respirator or approved powered air-purifying respirator.
Site of action Group 22: photosystem 1 electron diversion
Chemical family Bipyridilium