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Old 12-05-2007, 01:26 PM   #8 (permalink)
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Default Re: Once more about soft vs. hard water and Ca:Mg ratios

Well that obvious Ca , uptake, deficiency problem is one that I really want to takle.

This some info I collect around:
This element is found in its ionic form (Ca++) in the soil solution and in a hydroponic nutrient solution. This is also the form that the plant can absorb. Acidification of the nutrient solution when using soilless mixes can cause a slight reduction in the availability of calcium to the plant.

In sumerged plants:
Uptake reducing rapidly under 6.5 ph

Overall function:
In the cell, calcium can combine with bicarbonate to form the base, calcium bicarbonate, that is an effective neutralizing agent for acids formed during cellular metabolism.

Calcium uptake mechanism. (submerged plants)
Both Ca and Mg in land plants do not 'move' as readily in the xylem as other ions. The hypothesis is that because the movement of water through aquatic plants is less than in land plants, Mg requirements can't be satisfied by upward movement. At no time have I said that Ca and Mg can't move within the xylem of aquatic plants ... in fact experimental evidence clearly shows that at least Ca can move up or down in aquatic plants tissues (just not at a rapid enough rate to satisfy external requirements).

Calcium uptake mechanism. (Land plants)
Calcium uptake is by mass flow. Calcium contained in the soil solution moves into the root system with the influx of water and is carried in the transpiration stream to the various plant organs. Usually those areas with the greatest activity receive more water and therefore more calcium. Mass flow delivers more calcium than plants take up. Calcium uptake is generally genetically controlled. One of the restrictions is the fact that only newly expanding unsuberized root caps can absorb calcium. Any environmental factor that limits root expansion limits the uptake of calcium predisposing plants to physiological disorders.

Calcium and Nitrogen
Nitrate nitrogen tends to accumulate in the leaves and increase organic acid production, which increases the demand for Calcium to neutralize the acidity, if this calcium is in short supply calcium may be mobilized from the roots. This movement of calcium from roots is the demise of the root integrity and can lead to leaky roots and ethylene production signaling the plant to shut down.

In land Plants:
Problem with calcium uptake seems to be induced by factors that tend to limit the timely uptake or distribution of calcium within the plant. There are a number of factors that can contribute to this condition.

A low pH (6.0) or a high magnesium content can contribute to calcium deficiency.

[B]Natural water have a ratio of around 4:3 (to verify)[B]

With a ratio greater than about 5:11 of calcium to magnesium it may be of some benefit to add calcium even if you don't need to adjust your pH. Gypsum (calcium sulfate) is high in calcium but won't affect the pH. The best ph is 6.5 to 6.8
You can add calcium with Calcium sulfate or Calcium chloride

If your soil does not have either a low pH or a high magnesium content, over-fertilizing with potassium or nitrogen can influence the amount and distribution of calcium.

Last edited by Glouglou; 12-05-2007 at 03:38 PM..
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