That is one of my pet peeves. When zoysia or bermuda is mowed high it gets thatchy or fluffy, then someone trying to push PC lawn care says "you are fertilizing too much." True, if you starve zoysia, it survives and does not grow more than an inch or two in 12 months. However that lawn is also the color of straw most of the time. I do not get paid to make a client's lawn to look like straw. I give a lawn enough N to maintain color and density and insist it is mowed correctly. The way most fine lawns in Hawaii ended up being zoysia is in the 1990's most of the bermuda developed Take all patch. Homeowners were forced to resod. I think hybrid bermuda is one of the most disease susceptible grasses. If it is not Take all, it is dollar spot or leaf spot infecting it.
I spray liquid fertilizer through my boom all the time. That stuff is corrosive. I think a bare ground mix cannot nearly be as bad. Note the threaded caps on the end. That way, I can flush out the boom completely. I remove the caps, push water through, then remove nozzles and screens to clean those, put water through the nozzle bodies as well. Never had a problem with cross contamination. My bare ground sites are not far from landscaped areas. One of them is in a nursery. I am treating the roads and walk paths going through the nursery. Remember that there is no such thing as a 0-5 MPH wind day here and I do not spray on the rare day it is dead calm due to the danger of vapor damage.