I just spoke with our coop guy about going with fewer gpa to lighten the load on wet ground ... he said they use 20 gpa, and 15 would be a minimum.  I mentioned guys talking 3-5 .. he said planes can do lower, but they like more for better coverage ...

 Just relaying what he said ... I don't know .. I'm trying to figure out what pump to use for my little 9 nozzle  old rig I just got for my Mule.  A 50 gallon tank would sure go further at 4 gpa.