Which element is responsible for causing soil salinity? At what concentration does the soil become saline?

(N/A) Soil salinity refers to the accumulation of soluble salts in the soil.
Salts are a natural component of soil and water.
The ions primarily responsible for soil salinization are $Na^{+}$,$K^{+}$,$Ca^{2+}$,$Mg^{2+}$,and $Cl^{-}$.
Soil is considered saline when the concentration of soluble salts is $0.2 \%$ or above,or when the sodium concentration reaches $500 \text{ ppm}$ (sodic soil).