Very good question Harshraj.  I think , there will be much greater extent of salinity stress  under hydroponics compared to soil , at equivalent rates of electrical conductivity  as a function of NaCl. 

Broadly speaking the crops are more tolerant to salt stress when grown in hydroponic systems, especially NFT, than when grown in soil (SOARES et al, 2007).

SOARES, T. M.; SILVA, E. F. F. ; DUARTE, S. N.; MELO, R. F. ; JORGE, C. de A.; BONFIM, E. M. Produção de alface utilizando águas salinas em sistema hidropônico. Irriga, v. 12, p. 235-248, 2007.

 I think  hydroponic solution  is better than soil as you can control the salinity  levels by using   hydroponic  

thanks

Hi  Harshraj.

From the attached paper below. On p.4454, it states:

"Responses to salinity in hydroponics and soil may also be fundamentally different (Tavakkoli et al., 2010) and so to evaluate the relative effects of Na+ and Cl–, a soil-based system is needed to simulate the responses in field-grown plants."

Personally, I agree with the authors. For practical application, a soil-based system should be implanted for your research if you want to simulate the responses in field-grown plants. And I believe that most farmers grow pearl millet (your current research material) in soil.

You should also check out the paper by Tavakkoli et al., (2010) listed in the paper to see what are the fundamental differences between using soil or hydroponics method for salinity-resistant test. .

 Thank you all for suggestion .

Thats a very good point by Egidio , younwill have better control on EC of growing medium , but on the other side , it will not be representative of typical saline/sodic soil conditions , since specific ion effects and osmotic pressure effects , as a result of cumulative effects of all the ions , will distinctively missing . I feel , the results will also vary under two different conditions , because of these reasons.