Effect of subsoil's particle size on water and salt transport in layered soil

Effect of subsoil particle size on water and salt transport in layered soil with the loamy soils overlying sandy soils were investigated in a 2-D soil chamber. The results showed that finger flow occurs when wetting front enters into the subsoil, infiltration process changes from non linear into linear. The accumulative infiltration and the rate are higher in finer subsoil than that in coarser one. Behaviors of the salt and water transport in layered soils are different from that in homogeneous soils, and more water and less salt can be kept in the topsoil with coarser subsoil. The relationship between Cl- content and total salt content appears to be exponential function, however, the relationship between Na+ and total salt to be power function. The difference of Cl- content between two treatments is less than that of Na+ content when the total salt content is more than 20 g/kg; otherwise, the former is less than the latter. Moreover, Cl- content in coarser sandy soil is less than that in finer sandy one, which is completely opposite to the change of Na+ content. Obviously, adsorption of the finer sandy soil to Na+ is more than that to Cl- . As a result, the particle size of subsoil at layered soil has a great effect on salt leaching and water transport, which will provide useful information for planting field crop and irrigation in Xijiang region in China.