Eptam on first year Alflafa

First time I've ever planted hay last fall. I didn't use a residual control at planting.(regretting it after the fact) 

 

I see I can put Eptam on post emergence with irrigation.  My guess is the irrigation is used to get it down into the soil for the residual to work properly.  My field does not have irrigation, so my question is has anyone ever tried to spray Eptam on in the early spring during a good rain to wash it down into the soil?  Any luck or would I just be throwing money away? 

 

I had a plan to spray Pursuit in the late fall but my alfalfa did not germinate evenly. Some areas the alfalfa was not mature enough to spray and areas I could spray the weeds were to big for Pursuit to kill.  My main pest is Lambsquarter.

 

Thanks for any help.

Eptam on first year Alflafa