Growers who can mix a fertilizer solution and apply it at the right dose
somehow could not manage to put the correct dose of Osmocote;

The jar of Osmocote has a picture on it of exactly how much to scatter.
Although the picture means on a flower bed, I suspect the same amount would do
for a bonsai. It is very little.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)