Spatial variability of physico-chemical properties and hydraulic characteristics of a gravelly calcareous soil

Abstract

Due to the existence of gravelly soils and the lack of sufficient research on such soils, this study was carried out on a gravelly calcareous soil. Selected physico–chemical and hydraulic soil attributes were determined at 69 points on a nested-sampling design. Hydraulic characteristics including unsaturated hydraulic conductivity (K _ψ) and sorptivity coefficient (S) at six applied tensions of 0 to 0.2 m, and sorptive number (α) and macroscopic capillary length (λ) at five applied tensions of 0.03 to 0.2 m were determined using a tension disc infiltrometer. Hydraulic and chemical soil attributes were the highest and the lowest variants, respectively. The maximum and minimum values for the coefficient of variation (CV) in all the measured physico-chemical and hydraulic soil attributes were obtained for α_0.2 and soil pH, respectively. Minimum, maximum, mean and variance values of K _ψ, S and α decreased as applied tension increased. Although the pattern was reversed for λ. The majority of soil attributes showed the spatial structure with dominant spherical and exponential models for physico-chemical and hydraulic attributes, respectively. Range values of semi-variograms were obtained between 4.6 m (for α_0.03) and 211 m (for clay, gravel content and soluble Mg). In general, range values were 99.60, 82.05 and 40.2 m for physical, chemical and hydraulic soil attributes, respectively, indicating that the physical soil attributes influenced neighboring values over greater distances than the other soil attributes. This enables soil scientists to use measured soil physical data over greater distances to estimate attributes in the unsampled locations.

Keywords:

• hydraulic properties
• kriging
• gravelly soils
• tension infiltrometer