Water Infiltration Characteristics Research Articles

The Effect of the Construction of a Tillage Layer on the Infiltration of Snowmelt Water into Freeze–Thaw Soil in Cold Regions

The snow melting and runoff process in the black soil area of Northeast China has led to soil quality degradation in farmland, posing a threat to sustainable agricultural development. To investigate the regulatory effect of tillage layer construction on the infiltration characteristics of snowmelt water, a typical black soil in Northeast China was selected as the research object. Based on field experiments, four protective tillage treatments (CK: control treatment; SB: sub-soiling treatment; BC: biochar regulation treatment; SB + BC: sub-soiling tillage and biochar composite treatment) were set up, and the evolution of soil physical structure, soil thawing rate, snow melting infiltration characteristics, and the feedback effect of frozen layer evolution on snowmelt infiltration were analyzed. The research results indicate that sub-soiling and the application of biochar effectively regulate soil aggregate particle size and increase soil total porosity. Among them, at the 0–10 cm soil layer, the soil mean weight diameter (MWD) values under SB, BC, and SB + BC treatment conditions increased by 6.25%, 16.67%, and 19.35%, respectively, compared to the CK treatment. Sub-soiling increases the frequency of energy exchange between the soil and the environment, while biochar enhances soil heat storage performance and accelerates the melting rate of frozen soil layers. Therefore, under the SB + BC treatment conditions, the maximum soil freezing rate increased by 21.92%, 5.67%, and 25.12% compared to the CK, SB, and BC treatments, respectively. In addition, sub-soiling and biochar treatment effectively improved the penetration performance of snowmelt water into frozen soil layers, significantly enhancing the soil’s ability to store snowmelt water. Overall, it can be concluded that biochar regulation has a good improvement effect on the infiltration capacity of surface soil snowmelt water. Sub-soiling can enhance the overall snowmelt water holding capacity, and the synergistic effect of biochar and deep tillage is the best. These research results have important guiding significance for the rational construction of a protective tillage system model and the improvement of the utilization efficiency of snowmelt water resources in black soil areas.

Impact of textural layers in soils on irrigation infiltration processes in an oasis farmland, northwestern China

AbstractThe Hexi Corridor Oasis in China is an important agricultural area supported by extensive irrigation. The sandy soil in the area exhibits textural layering, which has marked effects on its properties. Textural layered soils play an important role in distributing and regulating water regimes in irrigated fields. However, little is known about the textural layering‐dependent variability in soil water infiltration characteristics following irrigation and the potential effects on soil hydrology and water regimes in these soils. The objective of this study was to determine water infiltration processes and their influencing factors for six soil profile types in an oasis farmland. Six in situ constant‐head infiltration measurements (with three replications in each of six sites) were conducted with a single‐ring infiltrometer in different soil texture configurations, and Hydrus‐2D model was applied to evaluate soil water distribution. The results showed that the wetting front depth for all treatments was in the following order: ST‐1 > ST‐5 > ST‐6 > ST‐3 > ST‐2 > ST‐4; the stable infiltration rate ranged from 1.2 to 3.3 cm/min during the investigation period in all treatments. The presence of a finer‐textured soil layer decreased water infiltration rates through the profiles, and the thickness and burial depth of textured layers had obvious effects on infiltration, compared with homogeneous sand profiles. Presence of a medium‐textured layer affected the infiltration characteristics and soil water spatial variability; driven by increased field capacity and the wilting point, hydraulic conductivity was correlated with soil variables that were related to soil structure, such as wilting point and field capacity, and less so with variables that were related to soil texture, such as the clay fractions (p < 0.001). These results suggested that textural layering altered the soil structure and caused heterogeneous infiltration of water, with implications for the distribution of irrigation water and prevention of deep percolation in this oasis farmland. The result of this study offers a new analysis of ponded single‐ring water infiltrometer data that the soil water infiltration is also influenced by the type of textural layered than just the irrigation system, which supports crop irrigation management in study area and other regions with similar soil regimes.

Infiltration Characteristics of Surface Water in Coal Seam Mining Beneath Gullies and Corresponding Preventive Measures

Infiltration Characteristics of Surface Water in Coal Seam Mining Beneath Gullies and Corresponding Preventive Measures

Runoff and infiltration characteristics of rainfall and snowmelt water on a model embankment slope composed of sandy soil simulating vegetation works.

Runoff and infiltration characteristics of rainfall and snowmelt water on a model embankment slope composed of sandy soil simulating vegetation works.

Modification of Green-Ampt model based on multi-stage characteristics of soil water infiltration

ABSTRACT Water infiltration in unsaturated soil is significantly affected by multi-stage characteristics that depend on the movement of the wetting front. We modified the Green-Ampt model to accurately capture these multi-stage characteristics during infiltration. The proposed model divides the water-infiltrated unsaturated soil into three zones, while the infiltration process itself is divided into three stages, with the quarter-elliptic wetting front curve being defined. The proposed model, together with other Green-Ampt based models, is analysed and compared with experimental investigations conducted in this study, as well as with published results from the literature. The results demonstrate the proposed modified model successfully describes the measured infiltration time for soil columns with different heights. Additionally, a parametric sensitivity analysis of the proposed model reveals the water infiltration process is mainly controlled by the hydraulic conductivity in the infiltrated zone and the suction head between the wetting front zone and the unpenetrated zone.

Infiltration and Leaching Characteristics of Soils with Different Salinity under Fertilizer Irrigation

Salt and nutrient transport and transformations during water infiltration directly influence saline soil improvement and the efficient use of water and fertilizer resources. The effects of soil initial salinity (18.3 g/kg, 25.5 g/kg, 42.2 g/kg, 79.94 g/kg, and 165 g/kg, respectively, labeled S1 to S5) on the infiltration and leaching characteristics of water, salt, and nitrogen were analyzed via a one-dimensional vertical fertilizer infiltration experiment. Meanwhile, the estimation models of cumulative infiltration and wetting front, including the effect of soil initial salinity, were established. The results showed that, with the increase in soil initial salinity, the cumulative infiltration within the same time decreased, and the migration time of wet front to 45 cm was longer. The time required for S5 to reach the preset cumulative infiltration was more than six times that of S1, and, for the wet front migration to 45 cm, the time requirement for S5 was about four times that of S1. In the established Kostiakov model and wetting front model, the coefficients all decreased with the increase in soil initial salinity, and the test index R2 values both reached 0.999. In the Kostiakov model, coefficient K had a linear relationship with the natural logarithm of initial soil salt content, while index a had a direct linear relationship with initial soil salt content. The cumulative leachate volume decreased with the increase in soil initial salinity, and the corresponding data of S3 and S5 were reduced by 37% and 57.3%, respectively, compared with S1. The electrical conductivity values of S1, S3, and S5 were 15.4, 209.8, and 205.6 ms/cm, respectively, being affected by the initial content in soil, soil moisture transport rate, and exogenous potassium nitrate (KNO3) addition. The NO3−-N concentrations in the leachates of S1, S3, and S5 at the end of leaching were 55.26, 16.17, and 3.2 mg/L, respectively. Based on the results of this study, for soil with high initial salinity, the conventional irrigation amount (2250 m3/ha) of the general soil in the study area could not meet the requirements of leaching salt. These results can provide a reference for the formulation of irrigation and fertilization strategies for soils with different salinity and contribute to the sustainable development of saline soil agriculture and the ecological environment.

Improving the Physical Properties and Water Retention of Sandy Soils by the Synergistic Utilization of Natural Clay Deposits and Wheat Straw

Improving the physical properties and water retention of sandy soils is of critical importance in arid and water-scarce regions such as Saudi Arabia. The impacts of organic amendments of different particle sizes coupled with natural clay deposits on improving the soil physio-chemical characteristics, nutrient availability, and growth of Sudan grass were investigated in this study. A loamy sand soil was amended with natural clay deposits at 2.5%, 5.0%, and 10% (w/w) application rates, and in combination with 1.0% (w/w) wheat straw of different particle sizes. The water infiltration, evaporation, and retention characteristics of the amended soil were studied for 9 weeks, and then Sudan grass was grown for 7 weeks. The impacts of the particle size of wheat straw on soil properties and nutrient availability were significant (p < 0.05) when combined with clay deposits. The highest application rate of clay (10%) demonstrated the highest water content (20.63–21.73%), and increased P and K availability to 35.54 and 6980 mg kg−1, respectively, in soil, which were 33% and 88% higher, respectively, compared to the control. Plant N, P, and K concentrations were increased to 0.95%, 0.26%, and 4.33%, respectively, which were 2–3.5-fold higher than the control. Therefore, the integrated application of natural clay deposits and wheat straw of fine particle size could be an effective strategy in improving plant production in water-scarce regions.

Soil water infiltration characteristics of reforested areas in the paleo-periglacial eastern Liaoning mountainous regions, China

Plantation forests (PF) and natural secondary forests (NSF) are the primary reforestation approaches. The establishment of PF can affect forest hydrological processes by changing soil structure. To date, few studies have focused on these changes and the effects on hydrological processes for the paleo-periglacial landform. To reveal reforestation approaches effects on water infiltration, including soil water infiltration capacity, retention capacity, and waterflow path pattern, we conducted field dye-tracer investigations with rainfall and laboratory infiltration experiments for the paleo-periglacial landform of eastern Liaoning mountains, China. The results showed that (1) Soil physical properties (including total porosity (TP), capillary porosity (CP), non-capillary porosity (NCP), initial soil water content (IWC), field water capacity (FWC)) and root abundance (RA) decreased with soil depth in both PF and NSF, while the soil bulk density (BD) and distribution of gravel content showed opposite changes. (2) Establishment of PF reduced the infiltration capacity and water retention capacity in the 0–20 cm layer, but enhanced the water retention capacity in 20–30 cm layer. Low IWC was conducive to increase soil water content (SWC) after infiltration. (3) Infiltration capacity parameters (including saturated hydraulic conductivity (Ks), SWC, difference between SWC and IWC (SWC–IWC), dye coverage ratio (DC)) were significantly correlated with BD, TP, CP, NCP, FWC, and fine roots RA (P < 0.05). Better connectivity gravels were more conducive to water infiltration. (4) Preferential flow was the main infiltration type, but with different waterflow paths pattern, with the 'funnel', 'finger' shape for PF, NSF, respectively. Increasing infiltration could increase flow path connectivity. Our findings show that soil physical properties, roots, and gravel occurrence affected soil infiltration, and different reforestation approaches had varying impacts on soil infiltration, water redistribution, transportation, and storage of surface and groundwater, improving the understanding of ecohydrological processes and effects of water resources management in forest ecosystems of paleo-periglacial landform.

Effects of Subsoiling with Different Wing Mounting Heights on Soil Water Infiltration Using HYDRUS-2D Simulations

Subsoiling is an essential practice in conservation tillage technology. The amount of disturbed soil at various depths resulting from subsoilers with different parameters has an important effect on soil properties (e.g., bulk density and water infiltration). The information regarding the effects of subsoiling on the characteristics of soil water infiltration is essential for the design of subsoiling tools. In this study, the effects of the wing mounting height (h) (75–155 mm) of the subsoiler on soil disturbance and soil water infiltration were modelled using HYDRUS-2D and validated using field experiments. Results showed that reducing h values resulted in larger soil disturbance area ratios, soil water infiltration rates (f(t)), distances of vertical wetting front movement (DVWs), accumulative infiltrations (AINs), and soil moisture contents at depths of 10–30 cm. The relationships among characteristics of soil water infiltration, h and time (t), were developed. The stable infiltration rates (fs) varied quadratically with h and the corresponding coefficient of determination (R2) was 0.9869. The Horton model is more suitable for describing the relationship between f(t) and t under the tested soil conditions, as compared with the Kostiakov and Philip models. According to the results of soil water content at different depths from the HYDRUS simulations and field experiments, the developed soil water infiltration model had a good accuracy, as indicated by RMSEs of &lt;0.05, R2 values of &gt;0.95, and mean relative errors of &lt;12%. The Above results indicated that increasing the hardpan disturbance by optimizing wing parameters of the subsoiler could improve soil water infiltration characteristics.

Interactions between flue gas desulfurization gypsum and biochar on water infiltration characteristics and physicochemical properties of saline-alkaline soil

The application of flue gas desulfurization gypsum (FGDG) improves the soil structure, reduces soil pH, and accelerates soil salt leaching. Biochar amendment to soil can affect the soil infiltration rate, increase soil porosity, decrease soil bulk density, and enhance the water retention capacity. This study investigated the interactive effect of FGDG and biochar on water infiltration characteristics and physicochemical properties as well as determined the optimal amendment rate as a saline-alkaline soil conditioner. Seven experimental schemes were designed, and the newly reclaimed cultivated soil from Pingtan Comprehensive Experimental Zone in Fujian Province, China, was used in an indoor soil column experiment to simulate soil infiltration. Five models were employed to describe the infiltration process. The power function was used to represent the dynamic process of the wetting front. The conclusions of this study are as follows: (1) there was a reduction in the infiltration capacity of saline-alkaline soil (sandy soil) in each treatment, and the application of FGDG alone had the highest inhibition effect compared to the control (CK). The Kostiakov model provides the best fit for the experimental data of soil cumulative infiltration. (2) All treatments increased the total porosity and water content of saline-alkali soil, with the combined application of FGDG and biochar found to be more effective. (3) The application of FGDG alone or in combination with biochar decreased the pH and increased the electrical conductivity of the saline-alkali soil significantly, with the combined application having the most significant effect. In contrast, soil amended with biochar alone had minimal effect on the pH and EC of the soil. (4) The best improvement ratio was achieved with the F1B2 combination (75 g/kg FGDG + 30 g/kg biochar).

Effects of Bio-Organic Fertilizer on Soil Infiltration, Water Distribution, and Leaching Loss under Muddy Water Irrigation Conditions

This study analyzes the soil water infiltration characteristics under muddy water irrigation and bio-organic fertilizer conditions in the current context of muddy water irrigation rarely being used in agricultural production and in combination with the problems of water resource shortages and low soil fertility in arid and semi-arid regions. An indoor one-dimensional soil column infiltration device was used for studying the effects of four muddy water sediment concentration levels (ρ0: 0; ρ1: 4%; ρ2: 8%; ρ3: 12%) and four bio-organic fertilizer levels (FO0: 0; FO1: 2250 kg·hm−2; FO2: 4500 kg·hm−2; sFO3: 6750 kg·hm−2) on soil water infiltration, evaporation characteristics, and leaching loss. The results demonstrated that a higher muddy water sediment concentration and fertilization level resulted in a smaller wetting front distance and cumulative infiltration amount within the same time, but the infiltration reduction rate (η) gradually increased. The three infiltration models (Kostiakov, Philip, and Horton) were fitted, and it was discovered that all three had good fitting results (R2 &gt; 0.8), with the Kostiakov model displaying the best fit and the Horton model exhibiting the worst fit. The cumulative evaporation amount and evaporation time in muddy water irrigation and fertilization conditions was consistent with the Black and Rose evaporation models (R2 &gt; 0.9), the Black model was proved to be higher than the Rose model. In comparison to ρ0, muddy water irrigation increased conductivity and total dissolved solids (TDS) in the leaching solution, but it reduced cumulative evaporation, soil moisture content, the uniformity coefficient of soil water distribution, and leaching solution volume. Compared with FO0, the application of bio-organic fertilizer increased soil water content and reduced soil water evaporation while also reducing the leaching solution volume, conductivity, and TDS in the leaching solution. The results of this research can provide scientific reference for the efficient utilization of muddy water irrigation and the rational application of bio-organic fertilizer.

Influence of Interlayer Soil on the Water Infiltration Characteristics of Heavy Saline–Alkali Soil in Southern Xinjiang

Interlayer soil is common in southern Xinjiang, because interlayer can reduce the infiltration rate of soil water. To simulate the interlayer soil in heavy saline–alkali cotton fields, this paper adopted a vertical one-dimensional infiltration test. T1 (315 mm), T2 (270 mm), and T3 (225 mm) and different interlayer positions (T5, 315 mm) and thicknesses of the interlayer (T6, 315 mm) with the same irrigation volume, as well as one perforation and sand filling treatment (T4, 315 mm), were set. The influence of different irrigation amounts, locations, and thicknesses of the interlayer and sand injection on water infiltration was analyzed. The analysis results showed that with the increase in irrigation amount, the water infiltration rate and the migration distance of the wet front increased, but did not penetrate to the bottom soil (90 cm). Under the same irrigation volume, the increase in interlayer thickness (T6) compared with the increase in interlayer position (T5), the change in soil moisture content in the upper and lower layers of the interlayer was greater, and the advance time of wetting front migration and cumulative infiltration were slightly higher. After tunneling and sand filling (T4), the infiltration rate of water was increased, the migration time of the wet front was reduced, and the profile water content of each soil layer was improved. The Kostiakov model could better simulate the water infiltration characteristics of interlayer soil with different profile configurations in heavily saline–alkali land. The results showed that in all of the treatments, only the wet front of the soil moisture reached 100 cm in the T4 treatment, and the maximum was only 87.8 cm in the other treatments, indicating that too little irrigation water or the upward movement and thickening of the interlayer were not conducive to water infiltration. For the interlayer soil area in the heavy saline–alkali land in southern Xinjiang, the appropriate irrigation water should be more than 315 mm. The treatment of drilling first and then filling sand can be used as a simple but effective measure to increase the water infiltration rate of the interlayer soil, and can thus be applied to the layered soil structure in the interlayer position of 60–80 cm.

Effects of urea solution concentration on soil hydraulic properties and water infiltration capacity

Elucidating the effect of fertigation on soil hydraulic parameters and water-solute transportation is fundamental to the design of farmland irrigation systems and their sustainable utilization. Few studies have focused on soil hydraulic parameters or water infiltration characteristics or how they are influenced by urea solution concentration. In this study, the clay loam and sandy loam in Yangling District of Shaanxi Province, China, were used as test soil, and experiments involving seven urea solution concentrations (0.2, 0.4, 0.6, 0.8, 1, 3, and 5 g/L) and a control treatment (0 g/L) were conducted to explore the influence of the various urea solution concentrations on soil hydraulic parameters and water infiltration characteristics. The results indicated that the cumulative infiltration and wetting front migration depth increased with urea solution concentration, as accurately estimated using the Kostiakov model and a power function, respectively. In addition, the coefficients of the Kostiakov model and the power function increased with urea solution concentration. Treatment with multiple concentrations of urea solution resulted in an increase in the volume of macro pores in the soil but a reduction in the volume of mesopores and micro pores in the soil, leading to increases in the saturated water content, saturated hydraulic conductivity, soil water diffusivity, and infiltration capacity and a reduction in the water-holding capacity of the soil. The effect of urea solute potential on the inhibition of soil water movement is small, and this inhibitory effect is far weaker than the improvement effect of the urea solution on soil structure, and hence enhance the soil water infiltration capacity. Our results increase the understanding of soil hydrological mechanisms and may be usefully applied for improving the management of fertigation.

Analysis of Water Infiltration Characteristics and Hydraulic Parameters of Sierozem Soil under Humic Acid Addition

The farmland in Yinchuan is composed of sierozem soil, which is characterized by high sand content and low organic matter content, resulting in poor water-holding capacity and weak soil structure. Humic acid is a natural organic polymer soil amendment. It is critical to study how humic acid affects soil water infiltration in sierozem soil at the microlevel. A one-dimensional vertical infiltration experiment was conducted to explore how adding different amounts of humic acid (0, 1%, 2%, 3% and 4%) affected the infiltration characteristics and hydraulic parameters of the sierozem soil. The results revealed that the wetting front and cumulative infiltration decreased with the increase in humic acid addition. When the infiltration time was 90 min, the wetting front of the 1%, 2%, 3% and 4% treatments was 6.50%, 10.00%, 15.00% and 21.00% lower than CK (0 for CK), and the cumulative infiltration volume was 4.50%, 11.14%, 18.42% and 23.60% lower than CK, respectively. Among the three infiltration models created by Philip, Horton and Kostiakov, the Kostiakov model (R2 &gt; 0.95) could more accurately describe the soil water infiltration process in the study area. After infiltration, the moisture content of each soil layer increased with the increase in humic acid, which improved the water-holding capacity of the sierozem soil. Using Hydrus-1D to calculate soil hydraulic parameters, we found that the humic acid addition affected the hydraulic parameters. With the increase in the amount of humic acid addition, the retention water content θr and saturated water θs were positively correlated with the humic acid addition amount and negatively correlated with the saturated water conductivity Ks and the reciprocal of air-entry α. The results showed that humic acid could increase the water-holding capacity of soil and improve the rapid water loss and poor water-holding capacity of sierozem soil.

Water infiltration and soil-water characteristics of compacted loess under applied vertical stress

Water infiltration and soil-water characteristics of compacted loess under applied vertical stress

Response and prediction of unsaturated permeability of loess to microstructure

The study of water infiltration helps to investigate the pollutants' migration, grasp the mechanism of the water cycle, and correctly evaluate water resources. This paper reveals the mechanism of compacted loess's one-dimensional vertical water infiltration characteristics using a low-cost water infiltration device. In addition, it investigates particle arrangement and pore size distribution characteristics using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The test finding suggests that the loess's early-stage infiltration rate is significant, and the dry density is not related to the infiltration characteristics. With the advance of the wetting front, the infiltration rate decreases under air resistance. The unsaturated permeability decreases with dry density at lower matric suction while unaffected by the dry density at higher matric suction. Moreover, the volume and connectivity of pores mainly control the water infiltration characteristics. Finally, based on the test results, a method for rapidly predicting the unsaturated permeability of loess is proposed. The results of the study help predict contaminant transport and guide groundwater extraction and management.

Study on Water Vertical Infiltration Characteristics and Water Content Simulation of Sandstone Overlying Loess

Research on the infiltration characteristics of surface water is fundamental for understanding the entire hydrological process. Therefore, studying the water infiltration process of sandstone slopes overlaid with loess and predicting soil moisture content are of great importance for investigating hydrological processes and controlling soil erosion in the hilly and gully areas of the Loess Plateau in China. This study mainly focuses on the simulation of the vertical water infiltration characteristics and water movement patterns of four kinds of sandstone (feldspathic and argillaceous sandstone) structures covered with thin layers of loess. In the one-dimensional vertical infiltration experiment and Hydrus-1D model simulation, the interlayer transition planes of loess–feldspathic and loess–feldspathic–argillaceous sandstones were found to present two conditions: fine soil covering coarse soil and coarse soil covering fine soil. Therefore, water infiltration reduced permeability. The existence of a transition layer between loess and feldspathic sandstone decreased the water infiltration rate and infiltration amount and decelerated the speed of the wetting front, thereby further affecting the ability of water infiltration. By using the Hydrus-1D model, 15 sets of soil hydraulic parameters, including θx (0.028–0.05795 cm3/cm3), θs (0.2306–0.4786 cm3/cm3), α (0.01899–0.06071 cm−1), n (1.438–6.408), and Ks (1.96·10−4–0.0576 cm/s) were inverted and optimized for each 20 cm soil layer (total of 60 cm). The Van Genuchten model constructed using these parameters demonstrated high accuracy in the simulation of water content in the vertical infiltration process of sandstone covered by loess with the coefficient of determination R2 &gt; 0.849 and relative error RE &lt; 5.311.

Water Flow Characteristics Controlled by Slope Morphology under Different Rainfall Capacities and Its Implications for Slope Failure Patterns

The high sensitivity of loess slopes to water has been emphasized in many studies. However, it is still limited in terms of the understanding of slope morphological differentiation on the overall and local failure patterns in slopes, as well as on the acquisition method of hydrological dynamics. In this study, rainfall characteristics and slope surface morphological differences were introduced. Geoelectric and environmental factors were monitored. On this basis, apparent resistivity corrected by seasonal temperature and its relationship with soil water content was calibrated. The water migration characteristics and potential failure patterns of three slope morphologies were evaluated. The results are: (i) the improved resistivity method can better reflect the water flow movement within the slope, and it performs well after being corrected by temperature; (ii) the characteristics of surface runoff and water infiltration are directly affected by the cumulative rainfall value, and especially when the cumulative rainfall is &gt;70 mm threshold, the surface runoff quickly infiltrates into the deep of the slope along the preferential paths; (iii) the interception ability of loess slope morphology to the surface runoff is concave slope &gt; convex slope &gt; linear slope; (iv) with the continuous rainfall, the convex surface of a slope is prone to be damaged by saturated mud flow. When the cumulative rainfall threshold is 70 mm, the preferential flow is easily excited on the concave surface of the slope, resulting in local collapse at the slope toe and mid-deep landslides.

Soil macroporosity and water flow in the root zone of oases in hyper‐arid regions

AbstractThe characteristics of soil macropores and water infiltration are closely connected to the growth of plant roots and their root zone environment. However, it is unclear how the root zone environment of oasis farmlands regulates the development of soil macropores and water flow in hyper‐arid regions. The objective of this study was to investigate soil macropores and their effect on water flow under irrigated oasis farmlands using a combination of X‐ray computed tomography (CT) and dye tracer. It was hypothesized that the integration of CT and dye tracer could clearly reveal preferential flow through biopores and large pores of oasis soils. A helical medical CT scanner was used to quantify more information about soil macropores in the root zone, along with an in situ single‐ring dye infiltration experiment to reveal water flow in three different oasis farmlands (piedmont oasis farmland, marginal oasis farmland, and old oasis farmland). Soil macroporosity was 0.44% under crop rows, while soil macroporosity in the interrows was only 0.30% across the oasis farmlands. Biopores contributed 73% of the volume of the total macropores under crop rows. The stable infiltration rate in the interrows was 0.3 mm min−1, which was significantly (p &lt; 0.05) less than that under crop rows (0.7 mm min−1). Water flow under crop rows were mainly transported in biopores and large pores. The contribution of macropores to preferential flow under crop rows was 4.8 times larger than interrows. The integration of CT and dye tracer was a more holistic technique, which adequately revealed that oases had preferential flow affected by biopores and large pores, resulting in higher solute and contaminant transport.Key Points Soil macropores and preferential flow affected by crop roots were investigated in hyper‐arid regions. The integration of CT and dye tracer adequately identified preferential flowpaths of oasis soils. Biopores were larger under crop rows than interrows. Preferential flow transported in biopores and large soil pores under crop rows.

The Dynamics Characteristics of Soil Water Infiltration and Capillary Rise for Saline–Sodic Soil Mixed with Sediment

Yellow River sediment is the potential resource for saline–sodic soil reclamation. Experiments of one-dimensional soil columns were conducted to investigate the upward and downward soil water transportation characteristics for saline–sodic soil mixed with different sediment addition (0, 10, 20 kg/m2 in the top 20 cm layer). The saturated hydraulic conductivity, ratio of macroporosity, cumulative capillary adsorption and infiltration rate all increased with the increase in sediment addition. No significant differences were detected for both the initial capillary rise rate and the initial infiltration rate for the upward and downward water transportation treatments, respectively. The average adsorption and infiltration rates showed an increasing trend with the increased sediment addition. The initial and average infiltration rates were higher than the initial capillary rise rate and average adsorption rates. The Philip model seems the optimal choice for the dynamic simulation of both upward and downward soil water transportation. The results may provide useful information for soil salinization amelioration.