Soil water characteristics of Middle Pleistocene paleosol layers on the loess Plateau

Abstract

Soil water plays an important role in water quality monitoring, irrigation scheduling, solute migration, and plant growth. The soil water condition for a field site depends on soil type and related water movement parameters. Information about the soil hydraulic properties of Middle Pleistocene paleosol layers within the Yingpan section on the Loess Plateau of China is necessary since it may affect water cycle processes both in vertical and horizontal directions; however, little data is currently available. The saturated hydraulic conductivity (K_s), soil-water characteristic curve (SWCC), field capacity, particle size composition, and other indices of the paleosol layers were determined. Out of a potential eight models to be fitted to the SWCC data, the van Genuchten model was applicable to four layers (S1, S5-2, S5-3 and S6) while the dual porosity equation was applicable to the S2, S3, S4 and S5-1 layers. These models fitted the data well. Results show that paleosol layers differed from each other in their capacity to hold water and this was related to their soil structures and porosities. These differences could be due to the different conditions prevailing during their formation. Although, paleosols occur at various depths, certain deep-rooting plants can access the water they hold. Therefore, the SWCC of the individual layers has significance for ecological management in the region.

Key words: Middle Pleistocene, paleosol, soil water characteristic curve, Loess Plateau.