My UTV sprayer is 25 gallons. And about 50- lbs when empty. Combined that's about 260 lbs in addition to the 1500 lb UTV.
My tractor weighs just shy of 6,000 lbs and would be using a minimum of a 40 gallon sprayer, putting the combined weight well above 6k.
Either way, under no circumstances would either of the above setups be doing 45 mph and routinely gunning the throttle in an attempt to spin the wheels.
Besides, last I checked...when spraying it is not recommended to repeatedly run over the same ground. It's the repetitive recreational use of the ditches that creates erosion. The twice yearly spraying barely leaves wheel tracks in the grass.
I can't believe I have to explain the difference in net effect on this.