Risk of using herbicide before laying sod?
I once laid a sod lawn and was soon plagued with grass weeds coming up through it. I swore I would do things differently the "next time". The next time has now arrived.
I recently killed with Round UP herbicide a bermuda grass invested lawn. I now plan to rotor till the native soil and add in some gypsum and compost, grade it and roll it. But before I lay the new sod (90% tall fescue and 10% Kentucky bluegrass)I wanted to thoroughly pre-irrigate the soil to activate the weed seeds and rhizomes near the soil's surface. Once they do, I plan to zap them with Round Up.
My concern is will the Round up residual in the dead new growth of weeds hurt the new sod that I plan to lay. I am being told different things?
How about if I use a pre-emergent herbicide instead? But will that kill the new growth of weeds from rhizomes? And most importantly will it harm the new sod?
My situation does not sound unique to me. Often people lay sod on soil that is not weed seed/rhizome free. What is the common practice when doing this?
I am not seeking well intentioned speculation as to the best course to take. Rather I hope to hear from knowledgeable people that have encountered my type of situation before and speak from personal esperience.
Thank you all very much.