Which formula is applied to calculate gypsum requirement (meq/I00gm)

Answer: Option C

Gypsum is a soft sulphate mineral composed of calcium sulphate dehydrate. It is used as fertilizer and helps soil better absorb water and reduces erosion also helps in the reclamation of soil.
The gypsum requirement (GR) is the calculated amount of gypsum necessary to add to reclaim the soil.

$$\text{GR}=\frac{\text{ES}{\text{P}}_{\left(\text{initial}\right)}-\text{ES}{\text{P}}_{\left(\text{final}\right)}}{100}\times \text{CEC}$$

ESP is Exchangeable sodium percentage.
CEC is Cation exchange capacity.