Can i use this to inject 3 gpm of fertilizer solution into a system operating at 70 psi with a 25 gpm flow?

I use it for chrysanthemums, I said it one to 100, 1 gallon fertilizer for 100 gallon water. It has all kinds of settings on it so it should work for you. I think your pressure should be OK.

Can I use this Dosatron for humic acids ?

We do not use humid acid in ours. Humid acid has some solid materials in it that may require constant agitation to keep it stirred up. The dositron has a screen but not sure if it would clog or reduce effectiveness. We have used humic acid in a sprayer system with an agitator. Sorry this is not a better answer. Best of luck!

Manufacturer	Dosatron
Part Number	D637922-D14MZ2 D14MZ2VFII
Product Dimensions	55.88 x 17.15 x 14.61 cm; 1.97 kg
Item model number	D637922-D14MZ2 D14MZ2VFII
Colour	Black
Style	Submersible
Material	Metal
Power Source	Water Pressure
Item Package Quantity	1
Flow rate	14 Gallons Per Minute
Batteries included?	No
Batteries Required?	No
Item Weight	1.97 kg

D14MZ2 D14MZ2VFII Water Powered DOSER 14GPM 1:500-1:50 D637922

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