General recommendations that I was given were to use sand as the soil medium to reduce saline build-up that you get with organic matter in the soil, additionally I used a flood irrigation as apposed to just enough to maintain soil moisture.  The idea was that each irrigation would wash out access salt and maintain desired salinity level.  The water for irrigation would be mixed prior to irrigation to the desired salt concentration, then applied.  There are also soil probes that can be utilized to monitor salinity.  This method does require fertilizer application which I did at a separate time from saline treatments and monitored/mixed to maintain saline appropriately.  While this is not a perfect method it did work fairly well for my bermudagrass germplasm screening, detailed studies are better with a salt table which allows more of a hydroponic method, but greatly limits scale.  Timing of saline application relative to plant maturity would be dependent on the objectives of trial, for my trials I did allow the materials some opportunity to establish in the pots but at the time I was working on turf grass.  I would suspect that your 4-5 leaf millet would be about the level of establishment I allowed my bermudagrass.

  The  method which i use is sand culture method, which is the best ,as you would not use hydroponics.  you should use 1.2 kg of pure sand into each pot, and put your plants in the sand culture for a period using  Hoagland solution ( half or full strength)2 . after 1-2 weeks, start your salinity treatment by preparing 200mM NaCl, using the molar  concentration of salt and then weighing the appropriate weight. this is method which i have been using in my physiological studies on salt stress for the last 25 years.

Harshraj Subhash Shinde did you find the right answer to your question?

Yes.

@harshraj could you please share it.

please check the attached publications.