I fully realize I can’t add in more alfalfa.

I got a field on lighter ground that the stand of alfalfa faded out real quick.   Last year was very hard on it between being on light ground and on the wrong side of have and have not for rain this year it’s sparse.   Some grass coming in but lots of weeds mainly marestail.   Looking to spray lite enough not to kill the alfalfa but burn back the rest.  What would you no till in the help the stand?   Orchard grass?   Fescue?    I got a grass box on my 750.