EC and osmotic pressure are positively related.Water relations are most affected because of high osmotic pressure built up in soil solution induced by EC from soluble salts..

The EC and the osmotic pressure measure the same thing: the concentration of chemical ions in the soil solution

Salinization is a threat world-wide to land degradation, and one of the most serious problem in agricultural production facing world. The status of soil water content is required to accomplish fluctuating salinity, and can be described, as follows:

a) the soil water content (SWC) > amount of water in soil,

b) soil water potential (SWP).

If You know SWP, You can identify energy level by which the water is held in the soil. Both parameter are closed to soil salinity. Soil salintiy is influenced by osmotic potential in the soil solution at any particular time. We can descibe osmotic potential as a function of the salt concentration in the soil solution (expressed as electrical conductivity = the total concentration of dissolved salts in soil solution directly related to field moisture) and soil water content. Generaly, EC should be used as the primary criterion of osmotic pressure affecting water uptake by plants.

Researches prefer indicate relation in the ratio of actual salt content using leaching curves. The same extent of leaching is required to know effect of soil type on the quantity of water. A large accumulation of ions in the plant leading to ion imbalance, and conseqently to osmotic stress resulting in poor plant growth crop is considered. EC is important in salt-affected soils, due to low soil microbial activity. Saturation soil extract of more than 4 dS/m at 25°C is boundry of osmotic stress. However, Soil Science Society of America indicate 2 dS/m at 25°C as a level of salt problem in yield and soil water leaching.

Understanding the interaction between osmotic stress and water content is important to maintain turgor of water, ameliorate saline soils, avoid wilting of plant, to study present of soil microbes, and to estimate the quantity of sufficient neutral soluble salt related to water movement.

You may find these article worth reading. Hope it will be useful to you.

http://www.zobodat.at/pdf/PHY_18_1_2_0071-0078.pdf

http://www.fao.org/docrep/003/T0234E/T0234E02.htm

https://books.google.co.in/books?id=jWFK5UgUG0IC&pg=PA164&lpg=PA164&dq=relationship+between+EC+and+osmotic+pressure+in+soil&source=bl&ots=vySQqQDQRw&sig=1SG3xTzeVgbugVx_geIiSEG4fCM&hl=en&sa=X&ved=0ahUKEwjixNTt-JHUAhULK48KHRSnBH0Q6AEITTAF#v=onepage&q=relationship%20between%20EC%20and%20osmotic%20pressure%20in%20soil&f=false

http://www.fao.org/docrep/x5871e/x5871e04.htm

https://dl.sciencesocieties.org/publications/sssaj/abstracts/13/C/SS01300C0066?access=0&view=pdf

http://www.sciencedirect.com/science/article/pii/S1674775513000711

https://books.google.co.in/books?hl=en&lr=&id=H6aHAwAAQBAJ&oi=fnd&pg=PP1&dq=relationship+between+EC+and+osmotic+pressure+in+soil&ots=BWNg2-Xb1I&sig=NPlLASBIgSnh0BhOr_80OPpr7h0

EC and osmotic pressure are positively related.Water relations are most affected because of high osmotic pressure built up in soil solution induced by EC from soluble salts..

OP = 0.36 × EC (EC in dS/m)

Indranil Das. precisely answered

Thanks all of you for valuable informations.

Osmotic Pressure  = 0.36 × EC (dS/m)

Such empirical relation between osmotic pressure and EC( nicely shown by Indranil Das)  , whether or not , it will vary according to type of salinity and within any range of EC..?

Indranil Das or Emad Aboukila - Can you please give some references to this formula?

Please give me more time so that I can provide you the references.

Okay. I'll be grateful.

It is based on the concept of competing interphase interactions in soil and develops the classical ideas by A.A. Rode. Upon the low soil water content, surface (molecular and ion-electrostatic) forces of the solid phase bind water molecules and prevent them from hydrating ions and dissolving electrolyte salts in the soil solution; as a result, electrical conductivity and osmotic pressure values approach zero in this case. With an increase in the water content, water molecules escape gradually from the energy field of surface forces, and their activity (chemical potential) and dissolving capacity also increase. This results in the expected growth of the electrical conductivity and osmotic pressure of the equilibrium solution extracted from the soil.