The 'green corridor' concept along the railway lines is an emerging research area in bio-engineering as form of subgrade soil stabilization. Native trees grown along rail corridors increase the matric suction of the subgrade through the root water uptake associated with the evapo-transpiration by the tree canopy. One of the most important aspects in subsoil improvement through native vegetation is the effect of osmotic suction attributed to solute uptake by active root hairs. The current study offers to capture the effect of matric and osmotic suction to overcome the existing empirical relations which are applicable mainly for site-specific controlled conditions. Moreover, the proposed computational model relates the water and solute uptake with the rate and magnitude of evapo-transpiration of tree canopy. The results show the importance of considering osmotic suction, especially in saline soil in the presence of trees.