@ Noora, salinity is a measure of soluble salts in soil and salinity can occur naturally where drainage is poor. In your case the pots are in similar condition and soils were irrigated with the same quantity of water having different NaCl level. Therefore, there should be gradual increase in salinity with the salt concentration. Please check your instrument and irrigation water.

I support the explanations given by Dr J.C.Tarafdar.

Relative

The short answer is no as given by JC Tarafdar