What implement would be best for knocking down weeds in rocky soil. I want to knock down weeds for fire prevention. Most of the rocks in the field are softball size. I don't think a rotary mower would work. How about a flail mower? Or a disc with no weight on it. I don't need to till it in, just knock down the weeds. I have been using a hand-held string trimmer but we are talking about three acres.