I can't give a complete opinion on your question.   I've never used Valor.  But have used trifluralin for over forty years.  In my opinion, it is a good product.   I believe the label says in needs to be incorporated within 24 hours.   Not necessarily, immediately.   

One concern I have with trifluralin, is it's five month rotation restriction to planting wheat.  That makes me nervous, since we often like to follow soybeans with wheat.   But if wheat planting isn't a goal for you, then rotation restrictions shouldn't be an issue for you.  

I don't think I've ever had a time when I wished we hadn't of incorporated a soil herbicide, but instead sprayed it over the top.  As long as the incorporation is light in nature, but thoroughly mixed in the top couple of inches.... I feel it gives us better odds of success, versus hoping for a rain to work in the herbicide.  



gordon