Quote:
Originally Posted by sunfire
I use rainwater and MSU rainwater formula. I probably had been under fertilizing it over the winter (fed at 50ppm N every week). I have increased the dose recently to 100 ppm every week.
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Let me throw out a couple of things that might help.
The MSU RO formula has plenty of magnesium, and supplementation is probably unnecessary, but...
A decent weekly feeding level is about 100 ppm NITROGEN, which for that formula, has a
true TDS contribution of 740 ppm (i.e., 0.74 g powder per liter of pure water).
I don't know how you determine your concentration, but if you've been feeding at a true TDS of 50 or 100 ppm, you've obviously been drastically underfeeding, but...
TDS meters are notoriously inaccurate, so don't trust the reading to be solid indicators of reality. You can use it as a control device though, making your own "calibration curve".
I had two TDS meters (now both trashed), If I remember correctly, for a known 100 ppm N solution of MSU RO, one said the TDS was 375 ppm, while the other said about 450.
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