Soil water retention curve of agrogray soils: Influence of anisotropy and the scaling factor

Abstract

Abstract-The soil water characteristic or soil water retention curve (WRC) of m edium -loam y gray forest soil horizons was studied in cylinder-shaped samples of disturbed and undisturbed structure. The sample height varied w ithin 2-4 cm and the diam eter w ithin 4.5-10 cm. The soil m onoliths were sampled in three profiles: vertically, along the slope, and across the slope in accordance w ith the intrasoil paleorelief form ed by the funnel-shaped surface of the second hum us horizon. The experim ental W RC were approxim ated w ith the van G enuchten equation. The statistical analysis of the W Rc approxim ation param eters proved to differ signifi cantly in filled soil samples and m onoliths, and a num ber of param eters differ for samples of the maximal height and diameter. T he reliable differences of the param eters were also noted for the different sampling directions, m ost often, for those across the paleorelief slope. The noted variation in the W RC approxim ation param eters may substantially influence the predictive estim ation of the spring water reserve for example. This fact suggests the necessity to strictly indicate the sampling procedure, in particular, w ith respect to the soil profile, the asymmetry in the soil properties, and the sample sizes (scaling factor) used for analyzing the hydrological properties of structured soils.