I have a question on what concentration of nutrients (mg/l) is too much for plants in that it can cause the leaves or roots to burn? I know of some people trying to add DIY tabs (containing 1 mg of dry KNO3) into their substrate, and then saying the roots of their plants were just burned. So to add dry KNO3 into the substrate seems to be bad idea (maybe too high concentration of K/NO3. When we are dosing dry salts into the water column the chemicals are diluted so its much more safe for plants as well as for us to reach some dangerous levels.
Does anyone know what levels are still safe (for water column vs. root fertilizing)? Better yet what is the critical level for each nutrient (NO3, PO4, K, Fe ...) before it harms our plants?
I know we speak a lot of EI dosing, so the IE recomended levels should be OK. But what about sediment levels? We're adding a different stuff into the sediment, but it seems no one knows how much is OK vs. how much can cause burning roots.
I'm quiete confused with this matter, because in ADA AS/PS there is quite (extremely) high concentration of NH4, PO4, Fe ... but still the roots have obviously no problem with it. So why they have problem with dry KNO3 ... ?
Any suggestions/ideas/answers welcomed.