Looks like Panicum,
If Roundup and Atrazine did not take it out,
Maybe you should try Roundup without any Atrazine,
Atrazine is Clay based,
Not really sure what purpose the Clay provides?
Controlled release?
Encapsulated release?
No one has explained this to me?
Maybe some other herbicides are formulated in a similar manner?
Roundup is neutralized when it comes in contact with the soil,
So Atrazine is antagonistic to Roundup.
Clethodim would be the next choice.