RO = reverse osmosis.
MgSO4 will chemically combine with nitrogen at a ph under 5.8. I use no more then 10ppm of the stuff. I did a test with epsom salt and added like a half cup to a one gallon pot. It grew well for a month about with no signs of stress. Then it began to yellow slightly but not bad. Once I transplanted her into a two gallon pot she came back to normal. Mg lock up is hard to get and deficencies are rarely seen as it is a microelement. MgSO4 will stay in your soil for a while increasing the ion content. Hard water limits the nutes your baby can uptake which is why some growers use under 100ppm every two to three days.
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