The Effect of Osmotic Pressure Gradients on Water Movement in Unsaturated Soil

Water movement, in response to osmotic pressure gradients, was measured in clay loam and sandy loam soils at soil water suctions from 0.08 to 15 bars. Movement in response to osmotic pressure gradients were compared to movement in response to hydraulic pressure gradients in the soil water suction range from 0.08 to 0.65 bars. At suction less than 0.5 bars, the amount of water moved by osmotic pressure gradients was generally less than 4% of the water moved by hydraulic gradients of equal magnitude.