There is a general empirical formula for conversion of EC to total dissolved solids (TDS).

TDS (mg/l) = EC (dS/m) * 640  (for EC range 0.1 - 5 dS/m)

The EC will vary with the type of salt used and there are other ratios for higher ECs. For a table of conversions see page 159 of

https://publications.qld.gov.au/storage/f/2013-12-19T04%3A10%3A23.754Z/salinity-management-handbook.pdf

Regards Andrew

There is a general empirical formula for conversion of EC to total dissolved solids (TDS).

TDS (mg/l) = EC (dS/m) * 640  (for EC range 0.1 - 5 dS/m)

The EC will vary with the type of salt used and there are other ratios for higher ECs. For a table of conversions see page 159 of

https://publications.qld.gov.au/storage/f/2013-12-19T04%3A10%3A23.754Z/salinity-management-handbook.pdf

Regards Andrew

Thank you Andrew Butler. But what if we need to irrigate with water of higher salinity like 6 and 8 dS/m for experimental plots? 

The conversion will be pretty close to that above, so around 3.84 g/L and 5.12 g/l for your test samples. You may need to adjust slightly depending on the quality of the salt.

Hi Dear Gaurav, 

I agree with Dr Butler about the relationship between TDS ( mg/L) and EC ( dS/m) , but the coefficient of 640 can vary withe concentration of the salt and also with salt type. 

you can use also the empirical formula :  C  ( mmolec/L°= 10*EC for converting  the EC to salt concentration.  

In my knowledge , Saline solution with higer Concentration tend to form ion-pair, and the concentration of the ion have no-meaning in this environement because it's the Ion activity that counts. 

Kind regards Louadj Yacine

The Relationship between electrical conductivity and the concentration of dissolved ions is a function of the major ions. If you want to prepare a solution of Nacl, then you should use the specific relation of Ec versus TDS for chlorides, and you can find it in the figure 11, page 68 of the USGS Water Supply Paper 2254 at :

http://pubs.usgs.gov/wsp/wsp2254/html/pdf.html

Based on this graph for a 2 dS/m (2000 micro S/Cm in the figure 11) you should have a solution of water and NaCl with Cl concentartion of around 410 mg/lit (the exact value of concentration should be computed on the curve for chloride) . It means that you need around 675 mg of NaCl solved in 1 liter of distilled water. 

by the way, how much water do you have used for solving the 1.17 Kg of salt?

Dear Gaurav Jha

Your question is incomplete w.r.t. salt name, vol. of saline water to be prepared.

It is appropriate to consult EC to TSS with the help of graphs for single salt or mixture of salts given in USDA Handbook 60; these graphs are reproduced in different books later, e.g. Saline-sodic soils by Bresler et al.; Salt affected soils by Ghafoor et al.; Water quality for irrigation by Ayers and Westcot etc etc.

For precise calculations and conversion you may consult the following papers available on Research Gate.

Ghafoor, A., T. Aziz and M. Abdullah. 1988. Dissolution of gypsum size grades in synthetic saline solutions. J. Agri. Res. 26(4): 289-294.

Ghafoor, A., M.M. Ahmad, S. Muhammed and N. Ahmad. 1988. Efficiency of gypsum grades and quality of leaching water for reclaiming a saline-sodic soil. I. Amount and solute concentration of effluents. Pakistan J. Agri. Sci. 25(3):239-249.

Ghafoor, A., M.M. Ahmad, S. Muhammed and N. Ahmad. 1989. Efficiency of gypsum grades and quality of leaching water for reclaiming a saline-sodic soil. II. Chemical improvement of soil. Pakistan J. Agri. Sci. 26(3): 313-321

Ghafoor, A., M.I. Shahid, M. Saghir and G. Murtaza. 1992. Use of high-Mg brackish water on phosphogypsum and FYM treated saline-sodic soil. I. Soil improvement. Pakistan J. Agri. Sci. 29(2):180-184

We can use this formula if we need to get EC more than 5 dS/m.

= TDS (mg/L ≈ EC (dS/m) x 800 for EC > 5 dS/m

I want to use mixture of sodium sulphate and calcium chloride salts . How can i get the EC 2,4 maintaining the same number of atoms of each salt in a mixture?