Raising lawn level - what to do with existing soil/weed
I am considering mass killing all the weeds before i soil/reseed in fall (my understanding is it's not a good time for new grass right now). I tried vinegar/salt/dishsoap method in paved area and it worked quite well in killing the weeds. Is there any issue to mass spray this onto the lawn? I heard that the vinegar/salt will permanently make the soil infertile, but since i will putting 3 inches of new soil, maybe it wouldnt matter?
basically 2 questions:
- How risky would it be to "kill" off the lawn before I add the new 3-inch soil on top? I want to make sure the new soil would be sufficient for new grass to grow later.
- I assume vinegar/salt is more "organic" than other herbicide. My kids will be playing in the backyard so i want to avoid using the really toxic herbicide. Any other recommendation for herbicide?