I do not know if some sparingly soluble Ca2+ compounds may occur, otherwise the Ca2+ in materials such as vermicompost may largely be weakly bound, i.e. could be displaced by the ammonium ion in (say) ammonium chloride solution. This is a standard soil method.

Dear Vishan, it may happen, because our experience is after addition of Tricoderma to vermicompost the percent Ca in vermicompost has been improved from 0.8% to 1.5%.

Thank you all for your contributions!

Mr. Tarafdar, do you have any published paper on the findings whereby the calcium content was improved? It will be most helpfull to my research work. Thank you