I recently saw this question asked. I want to see how many soil guys can answer this. Because the people building our cannabis soils and consulting our organic weed farms across the country can NOT answer this question.
I’ve heard manufacturers change rates depending on water due to carbonates binding up and making nutrient less available. Not just nutrients, evidently the herbicides are sometimes different based on the water as well. And then for foliars anything over 70ppm carbonates or so is considered undesirable.
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If the nitrogen is from calcium nitrate that answers the question. If it’s from urea or ammonium nitrate idk
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Just found the formulas- looks like they change the ratios of ammonium and nitrate. Since these are -/+ charged, they’d have different effects on soil acidity. Adding an acidity generating fertilizer with hard water would help neutralize some of the bicarbonate… that’s my final best guess.
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@grow yes ph stability sounds like the answer , good call : )
I would be concerned with the lack of p in the feed if I was using either of them as something extra to think about and amend
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19-4-23 is a macro/micro nutrient fertilizer formula created by MSU (Michigan State University) for growing orchids.
This formula just happens to be great for growing cannabis too.
The 13-3-15 is MSU’s fertilizer formula for using city water and RO water alike.
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Morning folks. Not all hard waters are created equal. A water test might show neither one is a good choice, depending on what’s in it. Just a curious guy.
City water used to eat my coffee pot in 3-4 months. State water I get 8 or 9 months now.
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This right here!
Trying to use my (midwest) tap water has been the bane of my existence. Commonly it’s around 300+ PPM right out the tap, springtime though after the winter thaw it can be over 400PPM.
I resorted to just refilling 5gal jugs at a local RO water refill station because the alkalinity is unmanageable, pretty sure my entire town is sitting ontop a huge limestone deposit or something.
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Can’t you offset that with gypsum or nah
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You know, I’m actually not sure. 
I’ve read that gypsum will help with alkaline soil but does that also apply to alkaline water? The difference may be that alkaline soil has a build-up of sodium carbonate, as opposed to the municipal water supply having a high concentration of water-soluble calcium carbonate.
Maybe someone with more mineral/soil smarts than me can chime in…
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