Once I have found this paper:
John Skok "Effect of the form of the avalable nitrogen on the calcium deficiency symptoms in the bean plant", and it seems like
kekon’s assumptions in How to balance NPK, Ca, Mg and micros - new experiments partially wrong.

John tested plants with Ca deficiency -Ca and CO(NH2)2 dosing VS. -Ca and NO3 dosing. I allow myself to quote:

«Calcium has been found to be one of the most important mineral elements needed for normal plant growth. In its absence plants exhibit very severe deficiency symptoms.»
«The reason that calcium deficiency has a more severe effect on a plant than the deficiency of almost any other single element is probably in part because calcium has been found to have many functions in growth and development.»
«If minus calcium plants lose their capacity to reduce nitrates and synthesize proteins, they are essentially minus nitrogen as well as minus calcium.»
«(1) Under normal conditions including the presence of calcium, urea is not as good a source of nitrogen as is the nitrate form for growth of the bean plant.
2) In the absence of calcium much better growth is made
by the bean plant with urea than with nitrates.»
«The form of the available nitrogen, however, has a very pronounced effect on the calcium deficiency symptoms. With urea, the calcium deficiency symptoms are much delayed and when they become evident they are very much less severe.»
“...calcium deficient plants have a lowered reductase activity since the calcium deficient plants receiving urea, which is a reduced form of nitrogen, make much better growth than do those receiving nitrates. The calcium-deficiency symptoms of the plants receiving urea, then, are really truer symptoms which can be directly assigned to the lack of calcium. Since other elements, namely potassium, phosphorus, and sulphur, were also found to be necessary for normal reductase activity by ECKERSON (3), it may be entirely possibly that their deficiency symptoms may also be lessened in severity with the use of urea.”

So there is no NO3/PO4 “overdosing” in very soft water.

Plants assimilate NO3 reducing it to NO2, than to NH2 and only than “eat” it up.
When Ca is in deficit plants just can’t assimilate NO3 at needed rates because they have big problems with reducing ability of NO3, so really it is not “overdosing” NO3, but general lack of N !
NH2 (urea, amino acids, guanidine nitrate) cures N deficiency of plants coused by lack of Ca giving them reduced form of nirogen, but again not the couse itself – lack of Ca.

As Tom advises lowering growth rates by lowering light intensity, or as someone may say lowering NO3/PO4 dosing to some degree cures simptoms, but again not the cause itself – lack of Ca/Mg.

So, overdosing of B and underdosing of Cu is not the case with such simptoms?
Lack of Cu at very low GH coused by lack of Ca, and intoxication with Boron is caused by lack of Mg.
Or we still have to dose TMG to fix the issue?
I see that Tom Barr is totally right that TMG helps because it has lowered level of B and elevated levels of Cu, so we can say TMG is “tuned” for soft water and effectively prevents mentioned disorders, while PMDD on Plantex CSM+B is not?

Give to tricky plants a little bit of shade (or shorter lighting peak)
keep GH not less than 4-6 dosing GH booster etc or mixing RO-water with tap water 1:4
give some part of N in amidic form
dose TMG or equal (less B, more Cu) instead of PMDD or equal
....and enjoy very fast growth rates with RO-water without any leaves distortion.


It is my understanding only.
Correct me if I am wrong, please.

naman