نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم و مهندسی خاک، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران.
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objectives: Infiltration is one of the most important hydraulic properties of soil, representing the entry of water into the soil, which usually occurs in a vertical direction. This soil property plays a crucial role in the natural water cycle and has significant implications for soil management. In semi-arid regions, this hydraulic property is particularly important not only for meeting the water requirements of rangeland and rainfed crops but also for reducing runoff and soil erosion. Several factors influence soil infiltration, and they can be generally categorized into three groups: (1) surface characteristics, (2) soil properties, and (3) climatic and environmental conditions. This study focused on soil physical properties, with the aim of quantifying the influence of a wide range of these properties on water infiltration and identifying the most important factors in selected soils in a semi-arid region.
Materials and Methods: To investigate the role of soil physical properties on soil water infiltration indices, 68 sites in a semi-arid climate of Zanjan province were selected. To capture sufficient variability for examining the effects of physical factors on soil water infiltration, the sites were chosen based on criteria such as land use type, vegetation cover, and soil texture, ensuring that the experiments were conducted on the predominant soils of the region. At each sampling site, 14 consecutive readings of infiltration depth were recorded at specific time intervals until the infiltration rate reached a steady state flow, for the calculation of various soil water infiltration indices. To evaluate soil water infiltration in detail, six key indices—cumulative infiltration (CI), initial infiltration (II), initial infiltration rate (IIR), final infiltration rate (FIR), mean infiltration rate (MIR), and effective infiltration depth (EID)—were determined. In addition to field infiltration measurements, disturbed and undisturbed soil samples were collected from the 0–60 cm soil depth as the active hydrological layer, and transferred to the laboratory. The following soil physical properties were determined: particle size distribution (PSD), gravel content, bulk density (BD), initial soil moisture, mean weight diameter of dry aggregates (MWDdry), and mean weight diameter and geometric mean diameter of water-stable aggregates (MWDwet and GMDwet).
Results: Pearson correlation analysis revealed that the MWDwet and GMDwet of water-stable aggregates were significantly correlated with all infiltration indices (p< 0.05). Bulk density also exhibited significant correlations with CI, II, FIR, and MIR (p < 0.05). Moreover, multiple regression results indicated that physical properties including BD, initial soil moisture, gravel content, PSD, and GMDwet are the main factors controlling water infiltration in these soils. According to one-way ANOVA, the soils were classified into four groups based on BD, MWDwet, and GMDwet. Significant differences were found among GMDwet groups in CI, II, and FIR (p < 0.05). Differences among the groups of MWDwet in CI and II were significant. Additionally, significant differences were found among the BD groups in CI. This study indicated that, along with soil structure, the particle size distribution of soils can affect soil structure and porosity and, in turn, impact water infiltration in semi-arid soils.
Conclusion: The results showed that MWDwet and GMDwet of water-stable aggregates, along with BD, have the highest correlations with soil water infiltration indices. These three soil physical properties can be considered the most important determining factors in explaining soil water infiltration. It was also found that PSD indirectly influences MWDwet, GMDwet, and BD and, consequently, affects soil infiltration behavior. These findings emphasize the importance of PSD and soil structure in the process of soil water infiltration in semi-arid regions.
کلیدواژهها [English]
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