Question
How to estimate cation exchange capacity and the presence of exchangeable cation (Ca) in the soil.

Answer
Hi Patricia;
Completely unnecessary testing. Just a waste of money.
If you follow a balanced organic program, the soil, nutrients will level themselves out.
an organic program is self adjusting to give the soil what it needs.
Yu only need this information if you are studying for your degree in Agriculture, and I don't do homework.
Charlotte