[APD] RE: K+ at high or low Ca values

["Steve Pushak" <teban at powersonic_bc.ca>]

Could Antonio Trmas' apparent problem with Ca uptake be caused by too high a
level of magnesium?

Terrestrial plants have problems with Ca deficiency with high K (saline)
conditions because the high salt level interferes with the transpiration
stream by making it difficult for the plant to take up and respire water.
There has to be a sufficient transpiration stream to conduct this mineral
because it is not easily transported. Aquatic plants would not have this
problem because the Ca is present in solution & does not rely upon
transpiration.

The mechanism for magnesium toxicity is different. Doesn't this mineral
interfere by substituting for Ca chemically?

Just a wild guess, but perhaps lowering the K level in the water can induce
enough transpiration to bring Ca from substrate interstitial water into his
Echinodorus to ameliorate the shortage?

We don't really know if the Ca levels in his water are sufficient since the
high GH levels might be disproportionately due to Mg. The Ca in the water
might be being used up.

Peat & organic material can absorb a great deal of calcium from solution by
exchanging lower affinity cations such as sodium & potassium.

I induced salt stress (leaf loss, red coloration) in my cherry trees a
couple years back when I fertilized with lime. My theory was that the lime
liberated enough salts by cation exchange from the manure-rich soil to
create a salinity problem.

Steve P

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