the weeds will return. granted if you spray it good right now, it'll kill all the weeds in a week or two, but after about 6-8 weeks there will be a few rains and warm weather and sunshine. the sun will get to existing weed seeds that are now free to germinate and grow because they aren't shaded.

i have some berms that were just packed with weeds. i sprayed them good, and it killed everything. but two months later it was just as thick with new weeds as it was when i sprayed them.

what do you use to plant with? i'm guessing you use an atv, small disk, and a broadcaster. in october the weeds will be pretty tall and you'd probably have to bush hog it.

maybe you could plant some roundup ready beans now? the next time you're up there (july?), hit it with roundup. come october the beans will be matured and the place should be relatively weed free, as the beans provided a canopy to keep the weeds from germinating, and what weeds did germinate when you planted you took care of with the roundup.