Abstract:

Soil salt crust has an important impact on soil evolution and ecohydrological processes in arid areas. There are few recent studies on water and salt distribution characteristics in salt-crust soils, and the influence of salt-crust thickness is not considered, leading to great differences in research results. Therefore, in this paper, four initial salt concentration treatments (0 g·L⁻¹, 10 g·L⁻¹, 150 g·L⁻¹, and 250 g·L⁻¹) were set to obtain different salt-crust thicknesses (4.5 mm, 6.6 mm, 7.3 mm) through laboratory simulation tests, and the soil-profile dynamics of water and salt were compared and analyzed using a partial repeated stepwise withdrawal method. The results were as follows: (1) Compared with the non-salt treatment, the thicker the salt crust, the larger the soil-profile water content, and the smaller the salt-content variation range. (2) At the end of the experiment, the water content distribution characteristics of the 4.5 mm salt-crust soil were similar to those of the unsalted treatment, and the water contents of the 6.6 mm and 7.3 mm salt-crust soils were significantly higher than that of the unsalted treatment (P<0.05). (3) At the end of the test, the minimum salt contents of the 4.5 mm, 6.6 mm, and 7.3 mm salt-crust soils decreased by 90.5%, 46.3%, and 32.1%, respectively, compared with their initial salt contents. The results confirm that salt-crust thickness has a great influence on the distribution of soil water and salt. Therefore, it is suggested that the influence of salt-crust thickness should be considered comprehensively in future research on distribution characteristics of water and salt.

Key words: salt crust thickness, distribution characteristics of water and salt, evaporation front, HYDRUS-1D model