Institute of Agrophysics, Polish Academy of Sciences, Doswiadczalna 4, 20-290, Lublin, Poland.
Sci Rep. 2021 Apr 15;11(1):8293. doi: 10.1038/s41598-021-86862-3.
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 cross-semivariogram. The studied region (140 km) 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 and ranged from 0.01 up to 11.54 m day. 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 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.
饱和导水率（K）是评估土壤水分运移和质量的关键特性。大多数关于 K 的空间变异性的研究都是在田间或更小的尺度上进行的。因此，本工作的目的是评估东南波兰较大区域尺度上 K 的空间分布及其与其他土壤特性的关系，包括固有砂、粉砂和粘粒含量、相对稳定的有机碳、阳离子交换容量（CEC）和随时间变化的水分含量（WC）、总孔隙度（FI）和表层（0-20 cm）的干体积密度（BD）。使用半变异函数和交叉半变异函数评估空间关系。研究区域（140 km）主要为渗透性强、肥力和生产力低的砂壤土，位于波兰东南部（波德拉谢地区）。平均砂和有机碳含量分别为 74%和 0.86%，其范围（%）分别为 45-95%和 0.002-3.75%。个别样本数量从 216 到 228 个（K、WC、BD、FI）不等，其他土壤特性的样本数量为 691 个。最佳拟合模型被调整到经验半变异函数（指数）和交叉半变异函数（指数、高斯或线性），用于绘制克里金图。结果表明，在所研究的土壤特性中，K 的变异性最大（变异系数为 77.3%），与总孔隙度呈显著正相关（p<0.05，r=0.300），与土壤容重呈显著负相关（r=-0.283）。通过自然对数和平方根变换得到正态或接近正态分布。平均 K 值为 2.597 m·day，范围为 0.01 至 11.54 m·day。在单一（直接）半变异图中，K 的空间自相关（范围）为 0.081°（8.1 km），而在交叉半变异图中，使用 OC 含量、质地分数和 CEC 作为辅助变量，K 的空间自相关（范围）有利地增加到 0.149°-0.81°（14.9-81 km）。生成的空间图允许勾勒出两个亚区，北部砂质（砂含量>74%）和粉砂质（粉砂含量<22%）部分的 K 值主要较高，超过 3.0 m·day，而研究区域南部的 K 值较低。一般来说，研究区域 K 值的空间分布取决于各个固有质地分数的份额。另一方面，K 与固有和相对稳定的土壤特性之间的空间关系范围（从~15 到 81 km）比 K 与随时间变化的土壤特性（0.3-0.9 km）之间的空间关系范围大得多。这些知识有助于做出与土地管理相关的决策，旨在改变水力传导率，以改善土壤水资源和作物生产力，并减少化学淋失。
