Variation in preferential flow features induced by desiccation cracks in physical crusts

Abstract

Studies have shown that preferential flow induced by cracks establishes multiple features such as morphology in different soil profiles. However, there has been little experimental evidence of the contribution of physical crust towards crack features and preferential flow. Essentially, this investigation focused on physical crusts (structural and deposition crust) of Lou soil, a loam and silt loam-textured soil, to demarcate the formation of cracks and preferential flow under artificial rainfall. The crack initiation and propagation processes were defined as the formation of primary cracks in the initial phase and narrow cracks around primary cracks, respectively. The cylindrical soil containers and cubical stainless-steel boxes were employed to trace preferential flow in the horizontal and vertical profile, respectively. The cracks in structural and deposition crusts were dominated by initiation and propagation cracks, respectively. The area, length, and width of the cracks in the structural crusts (5.7 cm2, 815, and 1.44 mm) were notably larger than deposition crusts (1.7 cm2, 604, and 0.96 mm). The maximum dyed depths of the structural and deposition crusts reached 35, 45, and 65 mm, and 35, 55, and 75 mm under the infiltration amounts of 10, 30, and 50 mm, respectively. The uniform infiltration depth, length index and PF-fr of structural crusts were in the ranges of 6.7 ∼ 25.5 mm, 19 ∼ 46 %, and 83 ∼ 111 %, respectively. Corresponding values for deposition crusts were 7.2 ∼ 26.2 mm, 10 ∼ 46 %, and 87 ∼ 103 %, respectively. The preferential flow in the soil profiles with structural crusts was superior to deposition crust. An assessment of the potential function of the physical crust for preferential flow is a supplement to study the effect of soil surface morphology on hydrological process.