Spatial variability of saturated hydraulic conductivity and its links with other soil properties at the regional scale
Streszczenie
Saturated hydraulic conductivity (K) is a key property for evaluating soil water movement and
quality. Most studies on spatial variability of K have been performed soil at a field or smaller scale.
Therefore, the aim of this work was to assess (quantify) the spatial distribution of K at the larger
regional scale in south-eastern Poland and its relationship with other soil properties, including
intrinsic sand, silt, and clay contents, relatively stable organic carbon, cation exchange capacity
(CEC) and temporally variable water content (WC), total porosity (FI), and dry bulk density (BD) in the
surface layer (0–20 cm). The spatial relationships were assessed using a semivariogram and a crosssemivariogram.
The studied region (140 km2)
with predominantly permeable sandy soils with low
fertility and productivity is located in the south-eastern part of Poland (Podlasie region). The mean
sand and organic carbon contents are 74 and 0.86 and their ranges (in %) are 45–95 and 0.002–3.75,
respectively. The number of individual samples varied from 216 to 228 (for K, WC, BD, FI) to 691
for the other soil properties. The best fitting models were adjusted to the empirical semivariogram
(exponential) and the cross-semivariogram (exponential, Gaussian, or linear) used to draw maps with
kriging. The results showed that, among the soil properties studied, K was most variable (coefficient
of variation 77.3%) and significantly (p < 0.05) positively correlated with total porosity (r = 0.300) and
negatively correlated with soil bulk density (r = – 0.283). The normal or close to the normal distribution
was obtained by natural logarithmic and root square transformations. The mean K was 2.597 m day−
1
and ranged from 0.01 up to 11.54 m day−
1. The spatial autocorrelation (range) of K in the single (direct)
semivariograms was 0.081° (8.1 km), while it favourably increased up to 0.149°–0.81° (14.9–81 km) in
the cross-semivariograms using the OC contents, textural fractions, and CEC as auxiliary variables. The
generated spatial maps allowed outlining two sub-areas with predominantly high K above 3.0 m day−
1
in the northern sandier (sand content > 74%) and less silty (silt content < 22%) part and, with lower K
in the southern part of the study region. Generally, the spatial distribution of the K values in the study
region depended on the share of individual intrinsic textural fractions. On the other hand, the ranges
of the spatial relationship between K and the intrinsic and relatively stable soil properties were much
larger (from ~ 15 to 81 km) than between K and the temporally variable soil properties (0.3–0.9 km).
This knowledge is supportive for making decisions related to land management aimed at alteration
of hydraulic conductivity to improve soil water resources and crop productivity and reduce chemical
leaching.
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