MadSci Network: Agricultural Sciences
Query:

Re: WHY DO WE HAVE A GREATER LEACHING OF CALCIUM THAN MAGNESIUM IN THE SOIL?

Date: Fri Nov 20 02:19:37 1998
Posted By: Bo Stenberg, Post-doc/Fellow, Soil microbiology/ecology, Swedish University of Agricultural Sciences, Department of Microbiology
Area of science: Agricultural Sciences
ID: 910638351.Ag
Message:

The main reason is that there generally are more soluble Ca-ions present in 
the soil. Roughly there is about ten times more Ca than Mg. The 
leachability of ions in soil depends mainly on two things: The electric 
charge and the hydration. Both Mg and Ca have two valence electrons and 
consequently the ions have a two-fold positive charge (2+). This make them 
both relatively strongly bound to the negative charges on mainly 
clay-particles (or colloids) and humus. However, Mg2+ is slightly more 
hydrated than Ca2+. This make the ion larger and slightly looser bound to 
soil particles. Subsequently the Mg-ion is more prone to leaching then the 
Ca-ion. This difference, though, is not large enough to compensate for the 
richer occurrence of calcium in the soil. Acidification of the soil will 
increase the risk of leaching as hydrogen ions will occupy some of the 
negative charges instead of Ca, Mg and other positive ions.

Not being a specialist on the nutrition of fish I do not think that the 
fish directly takes up this calcium (or magnesium). It probably has to go 
through the food chains first, starting with plants and microbes.




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