Thanks for all the info.
I think DanO. is correct. I check with a local farmer and he also said it is to produce a growth spurt for the Roundup to work better.

I could not find any. I sprayed my field this past weekend with Roundup. Will check on it next weekend and spray again.

I have no way to cut the dead grasses in the field prior to seeding. Can I seed and let the rain do the work??
Will the dead grasses provide shade to maintain soil moisture?