Not magic, but I think the "downdraft" from any aircraft merely replaces the pressure driven droplet speed out of a typical ground sprayer boom. 

The downdraft of the aerial applicator is also relative to it's gross weight. As the load decreases, so does the lift demand. This equals less downdraft. Not so with typical ground boom spray nozzles.

Maybe we need to stick with 20 gpa in ground sprayers. I'd just like to see proof that 2-5 gpa doesn't work in ground sprayers as well as it does in aerial. Actually I think most aerial is 2 gpa. I'm not saying 2 gpa doesn't work in aerial, I'm asking for testing to see if it works for ground sprayers.