I use store bought vegetation killer. I think the main ingredient is glycophosphate or something that looks like that word. If you buy it at one of the farm stores it is usually about a 44% solution and a gallon goes a long way when mixed with water as directed.

They sell similar stuff at Lowes and Home Depot but the concentration is way less, it doesn?t cover as much, and generally doesn?t work well.

If I were you I would make a trip to your closest farm and ranch store and see what they have.