If the contents of exchangeable ions (cmol kg<sup>-1</sup>) determined in soil are Na<sup>+</sup> = 5, K<sup>+</sup> = 5, Ca<sup>2+</sup> = 10, Mg<sup>2+</sup> = 2, H<sup>+</sup> = 1, Al<sup>+3</sup> = 1, Cl<sup>-</sup> = 1.6 and HCO<sup>-</sup><sub>3</sub> =0.4, the CEC of soil is

Correct Answer: 24 cmol (P<sup>+</sup>) kg<sup>-1</sup>
CEC is cation exchange capacity is a measure of the soil’s ability to hold positively charged ions.
If the contents of exchangeable ions (cmol kg-1) determined in soil are
Na+ = 5
K+ = 5
Ca2+ = 10
Mg2+ = 2
H+ = 1
Al+3 = 1
Cl- = 1.6
HCO-3 = 0.4
Summing up all the values of positive ions, we get the value of CEC of soil i.e. 24 cmol (P+) kg-1