Soil Infiltration Characteristics Research Articles

The Infiltration characteristics of expansive soil subjected to drying-wetting cycles under surchage

This study investigates the infiltration characteristics of expansive soil subjected to drying-wetting cycles under surcharge. Infiltration tests are conducted on undisturbed expansive soil over four drying-wetting cycles. Additionally, the permeability coefficient under loading is determined prior to any drying–wetting cycles. Within the context of this study, the sample heights after drying and after wetting are monitored to determinethe natural swelling and shrinkage deformations. Experimental results show that the infiltration rate decreases asthe presssure increases. The sample’s swelling–shrinkage deformation decreases with each progressive drying–wetting cycle, whereas the infiltration rate consistently increases. The infiltration curve under the drying–wetting cycle can be divided into three stages according to the infiltration characteristics, which is significantly different from the infiltration curve of the sample without the drying–wetting cycle. Moreover, the proposed model can fit the infiltration curves well, and its fitting parameters are described using dimensionless pressure and the number of drying-wetting cycles.The drying of the expansive soil produces cracksthat are advantageous for infiltration. Additionally, the microscopic connection between aggregates reflects changes in the internal structure of the soil during successive drying–wetting cycles. As the number of drying–wetting cycle increases, small particles aggregate into large aggregates, and the contact relationship between the aggregate changes from face–face to point-point contact, reducing the swelling potential and increasing the porosity and infiltration capacity of the soil.

Changes in preferential flow caused by root effects in black locust plantations of different stand ages in the semi-arid region of the Loess Plateau

Preferential flow significantly influences regional water cycles, and affecting surface and subsurface runoff processes. By comparing soil infiltration characteristics across various forest ages, it can be evaluated how artificial black locust forests on the Loess Plateau contribute to the resilience of soil and water conservation. In this study, we analyzed the spatial distribution characteristics of roots of black locust plants using field investigations and statistical analyses and determined the effects of the root characteristics on the preferential flow in the semi-arid of the Loess Plateau, China. The results showed that the root biomass, root length density, and root volume ratio of young forests were significantly lower than those of middle-aged and mature forests (P < 0.05), and root characteristic parameters varied significantly among different root diameters and soil layers.. The average volume of decayed root channels in mature forests, accounting for approximately 0.16 % in a unit volume of soil, was 3.1 times that of young forests and 4.9 times that of middle-aged forests. Preferential flow increased with forest age in artificial black locust forests. 2–5 mm, 30–40 mm and > 50 mm roots promoted preferential flow to varying degrees, while roots of 5–15 mm inhibited the preferential flow. < 2 mm, 10–30 mm and 40–50 mm roots has no effect on preferential flow (P > 0.05). The size and density of decayed root channels significantly improve soil preferential flow, and the differences among forest ages are linked to the network created by rotten roots. These findings indicate that living roots of different diameters and decayed roots contribute to soil preferential flow to varying extents. The results provided a conceptual basis for understanding the potential impact of vegetation roots on surface runoff during the vegetation restoration ecosystems process in the Loess Plateau.

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 &lt; 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.

Study on rainfall infiltration characteristic parameters of unsaturated soil

The study of the rainfall infiltration mechanism of unsaturated soil has always been a hot issue in the field of geotechnical engineering. It is worth studying which parameters should be introduced to characterize the infiltration characteristics of unsaturated soil in the calculation and analysis of rainfall infiltration. In this paper, the Fredlund–Xing model was quoted in the SEEP/W module of the Geostudio software, and the transient numerical calculation of rainfall infiltration under the same rainfall duration T and different rainfall intensity I was carried out for a soil column. Three infiltration characteristic parameters were introduced: rainfall infiltration front depth WF, suction reduction depth MRn, and section infiltration rate IR. The variation of these three parameters and rainfall intensity I during rainfall were sorted out and analyzed; it is indicated that WF increases with the extension of rainfall duration. MRn decreases with the increase of suction reduction rate n%, and when the rainfall duration is 24 h, the maximum depth of the soil column affected by rainfall is approximately 35% of the total depth. IR is mainly affected by the rainfall intensity I and the saturation permeability coefficient ks. There is a limit value for the influence of I on WF, MRn, and IR, and the limit rainfall intensity under the calculation conditions in this paper is I = 2.5ks.

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.

An Integrated Approach to Evaluating Crop Water Requirements and Irrigation Schedule for Optimizing Furrow Irrigation Design Parameters in Kurnool District, India

In Kurnool district, due to the hot, arid climatic conditions, proper study of crop evapotranspiration and its effect on crop water demand for various crops is an extremely important issue. More focus will be given to the design and development of surface irrigation systems based mostly on furrow irrigation, as the rainfall pattern for this district was irregular in 2005. The crop water requirement and furrow irrigation design parameters for optimising the beneficial utilisation of available water resources and field performances are studied in this research. Some major crops, such as cotton, sugarcane, sorghum, maize, and sunflower, are considered when adopting a suitable furrow irrigation system for soil conditions of the types black clay, red loamy, and medium loam. The reference crop evapotranspiration was estimated for 2005 based on the Penman–Monteith equation as per FAO guidelines by the CROPWAT 8.0 model. Crop Water Requirement (CWR), Net Irrigation Requirement (NIR), and Gross Irrigation Requirement (GIR) were determined for available climatic and soil conditions. Soil surface characteristics were studied using AQUACROP 6.1 and compared with CROPWAT 8.0 for model accuracy. Various conservative and non-conservative crop characteristics were studied under limited set conditions, and correlation equations were developed between different parameters. Moreover, different furrow irrigation design parameters were considered by FURDEV (a module of the SURDEV model) for three modes of operation (i.e., fixed flow, cutback flow, and tailwater reuse method) under modified SCS (Soil Conservation Service) families of soil infiltration characteristics. NIR values were 200 mm, 1423.2 mm, 220 mm, 150 mm, and 150 mm for cotton, sugarcane, maize, sorghum, and sunflower, respectively. A maximum significant dry yield was observed for maize (13.586 tonnes/ha). Additionally, the maximum application efficiency and storage efficiency were obtained at 95.5% for sorghum and 99.3% for sunflower, which would be a beneficial outcome of this research. In general, the results of this research might be very effective for the irrigation authority of Kurnool District to plan suitable approaches for designing and developing proper water management systems.

Effects of different vegetation restoration types on soil infiltration characteristics in severely eroded subtropical regions of South China

Vegetation restoration could cause variations in soil and near-surface properties, altering soil structure directly or indirectly and consequently affecting soil infiltration characteristics. This study is aimed at exploring the variation of soil physicochemical properties and infiltration characteristics under five vegetation restoration types (including restored forest, restored orchard, restored scrubland, restored grassland, and unrestored eroded land, which are referred to as RF, RO, RS, RG, and EL, respectively) and the main factors affecting infiltration characteristics. The EL was taken as the control group. Five hydraulic heads (0, −3, −6, −9, and −12 cm) were set to continuously measure the soil infiltration characteristics through a disc infiltrometer. Results indicated that vegetation restoration types significantly affected initial infiltration rate (IIR), steady infiltration rate (SIR), and hydraulic conductivity (K), which ranged from 0.56 to 4.40, 0.32 to 2.86, and 6.48 × 10⁻³ to 0.47 mm h⁻¹, respectively (mean value: 2.72, 1.35, and 0.32 mm h⁻¹, respectively). The highest value of soil infiltration rate appeared in the EL, and the lowest value was observed in the RF. Root parameters including root length density and root surface density were highest in RG, and lowest in the control and RF, respectively. In addition, the conceptual path model explained 95%, 96%, and 96% of the variance in IIR, SIR, and K_s, with the goodness-of-fit index of 0.988, 0.988, and 0.997, respectively. This modeling determined biological crust thickness, soil organic matter content, root length density, and sand content as the major factors affecting the process of soil infiltration. These results enhance our understanding of the water erosion process under different vegetation restoration types in the severely eroded subtropical regions of South China.

Experimental Investigation of Water-Retaining and Unsaturated Infiltration Characteristics of Loess Soils Imbued with Microplastics

Microplastics are abundant in agricultural soils and have significant impacts on rainfall infiltration and soil water-retaining capacity. To explore the effect of microplastics on agricultural soil permeability by simulating the rainfall irrigation process, a one-dimensional vertical soil column rainfall infiltration test device was used to study the unsaturated infiltration characteristics of loess soil imbued with microplastics under rainfall conditions. The following conclusions could be obtained: the microplastic content (q), the microplastic particle size (p), and the soil density (γ) have effects on rainfall infiltration; the soil water-retaining capacity would be weakened owing to the existence of microplastics; and intermittent rainfall is preferred in agricultural irrigation. Finally, the permeability coefficient (k) and average flow rate (V) of the unsaturated soil are deduced together, and the relationship between the permeability coefficient (k) and the matrix suction (ψ) of the unsaturated loess soil containing microplastics is calculated by an example, proving good consistency between the experimental results and theoretical calculations. Microplastics represent negative effects on rainfall infiltration and soil water retention, so it is recommended to dispose of them.

Simplified approach for determination of parameters for Kostiakov's infiltration equation

Abstract Knowledge of soil infiltration characteristics is required increasingly for the proper design and efficient management of irrigation. Various empirical and physically based infiltration models have been used for several years, but the practical use of many is limited by parameter determination problems, which, in turn, are influenced by factors acting at the surface and within the soil, initial and boundary conditions, etc. In this study, a simplified approach for determining parameters for the Kostiakov equation was tested and validated. The equation's linearized form, using logarithmic transformation and field data collected from five sites, was employed. The results show that cumulative infiltration can be described well using the approach. Its quality is also confirmed by performance indices like R2 and standard error, whose values ranged from 0.985 to 0.999 and 0.020 to 0.005, respectively, suggesting that the simplified approach described is sufficient for practical purposes, when data are too scarce to apply other, complex methods to predict cumulative infiltration.

Performance evaluation of infiltration models under different tillage operations in a tropical climate

Land management practices have the propensity to influence soil infiltration characteristics and predictability of infiltration models. This study was conducted to evaluate the performances of the Kostiakov model, the Philip model and the Horton model in predicting cumulative infiltration depth under four tillage systems in a sandy clay loam: (i) No Tillage (NT), (ii) Reduced Tillage (RT), (iii) Ploughing followed by Harrowing and Ridging (PHR), and (iv) Deep tillage followed by Ploughing, Harrowing and Ridging (DPHR). Using the double ring infiltrometer to measure the infiltration rate, the observed data was fitted to the infiltration models and their goodness of fit was verified by Root Mean Square Error (RMSE), Mean Absolute Error (MAE), coefficient of determination (R2), Nash Sutcliffe efficiency (NSE) and paired sample t-test. The results show that the Kostiakov model exhibited the highest accuracy with the highest R2 and NSE values (R2≥0.9967 and NSE ≥ 0.9965) and lowest errors (RMSE≤ 1.16 mm and MAE ≤ 0.98 mm). The comparison of the performances of the models in predicting the cumulative infiltration depth revealed that the Kostiakov model is superior to the Philip and the Horton models under all the Tillage systems, as the Philip and the Horton models underestimated and overestimated the observed data at the initial and latter parts of the experiment, respectively. The observed and predicted cumulative infiltration depth compared using the paired sample t-test showed that the Kostiakov model was better than the Horton and the Philip models under NT, RT and PHR, while the Horton model predicted better on the DPHR than the Kostiakov and the Philip models. The infiltration capacities of the conservation tillage practices (NT and RT) were higher than the conventional tillage conditions (PHR and DPHR). However, the performance of the evaluated models in predicting cumulative infiltration shows that the measured infiltration was best simulated for the DPHR followed by the PHR, RT and NT tillage practices. From our study the Kostiakov model precisely predicted the cumulative infiltration depth relative to the Horton and Philip models. It is, therefore, the preferred choice for modelling cumulative infiltration depth in the ochrosols of the study area and under verified field conditions, these models can be applied to determine the suitable infiltration characteristics to minimise deep percolation and run off losses in irrigation scheduling.

The Influence of Rainfall and Evaporization Wetting-Drying Cycles on the Slope Stability

The decay of soil strength and the change of soil infiltration characteristics caused by the dry and wet cycle effect generated by the rainfall-evaporation process are important factors that induce slope instability. How to consider the effect of soil strength decay and water-soil characteristic curve hysteresis effect on transient stability change of slope is the key to solve this problem. In this paper, transient stability analysis of slopes considering soil strength decay and water-soil characteristic curve hysteresis is carried out based on Geo-Studio. The results of the study showed that the change of transient safety factor of the slope caused by rainfall-evaporation dry and wet cycle process has an overall decreasing trend and the safety factor decreased by 43% compared to the initial state. The seepage characteristics of the rainfall-evaporation dry-wet cycle have certain regularity. The location of slope measurement points has a greater influence on the magnitude of the pore pressure change: foot of slope &gt; middle of slope &gt; top of slope. Also, there is a significant response hysteresis in the change of pore pressure with increasing depth at the same location. The rainfall intensity has a certain influence on the change of slope safety factor, but its influence is not obvious when the rainfall intensity exceeds a certain amount.

Morphometric Analysis of Chilenahalli Micro-watershed in the North-eastern Dry Zone of Karnataka using GIS and Remote Sensing Techniques

The structure and landform of watershed and their associated stream networks are described mainly by their morphometric parameters and Watershed analysis based on morphometric parameters is very important for watershed planning, since it gives an idea about the basin characteristics regarding slope, topography, soil condition, runoff characteristics, surface water potential and quantify the linear, areal and relief aspects of watershed. Geographic information system and remote sensing techniques were employed for the identification of morphological features, drainage pattern and its planning in basin area. The Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) 30m resolution was used to digitize study watershed and generate drainage pattern and analysis done using GIS software and excel spreadsheet. The study reveals that Chilenahalli micro-watershed designated as 4thstream order and drainage indicate dendritic pattern with mature geomorphic stage and stream order verifies the Horton’s law of stream number. The Mean Bifurcation Ratio was found to be 4.46, which indicates low rainfall, shallow weathering and low dissection of the valley and it shows low to medium relief aspect during investigation of the basin. This can be visualised using DEM, relief ratio, ruggedness number, and slope maps of the study area. The drainage density was found to be 2.13 km/km2which indicate a low class Dd value, thereby indicating a poorly drained watershed with low response to hydrological parameters. The texture ratio of the micro-watershed is 3.52, which indicated coarse texture of drainage basin and the values of Form Factor, Circulatory ratio and Elongation ratio may imply an oval shape of the basin with a slightly elongated main stream and the length of overland flow values in this study is 0.23 km which shows moderate infiltration and percolation characteristics of soil. The study which also helps in planning erosion control strategy, prioritization of watershed and management practices for soil and rainwater conservation. The research study helps to formulate the selection and adoption of crop management practices by preparing soil map of the watershed in future.

Influence of Reclaimed Water Quality on Infiltration Characteristics of Typical Subtropical Zone Soils: A Case Study in South China

Irrigation with reclaimed water (RW) can alleviate water scarcity and improve the environmental and economic benefits. However, RW contains a large number of salts, suspended particles, organic matter, etc., which can affect soil infiltration. Previous studies focused on the examination of this effect in alkaline soils, but the infiltration change of acidic soils has seldom been investigated. This study selects four typical types of soil in the subtropical area in the south of China and designs experiments using different concentrations of RW to examine the influence of RW on the infiltration of various acid soils. The short-term impact is examined based on a one-dimensional horizontal method, and the long-term infiltration characteristics are measured by a Mini Disk infiltration meter with one year’s RW irrigation. Results show that RW irrigation can restrain the short-term infiltration of red soil while accelerating that of purple soil, aquic soil and paddy soil. Regarding the long-term effect, the cumulative infiltration of red soil increases with the decline of the concentration of RW, while there is no unique trend for the other soils. After one year’s RW irrigation, physical properties such as soil particle size distribution, texture and EC have changed. For red soil, EC increased significantly with RW irrigation, from 46.7 µS/cm to 101.07 µS/cm. However, regarding aquic soil, EC decreased from 157.05 µS/cm to 123.20 µS/cm. Moreover, the infiltration rate coefficient of red soil and aquic soil exhibits a significant positive correlation with RW concentration (p &lt; 0.01), while the silt content shows a significantly negative correlation (p &lt; 0.01). Furthermore, soil infiltration parameters c and S value of the purple soil, paddy soil, is significantly negative correlated with pH value (p &lt; 0.01). The results reflected that appropriate RW quality for irrigation is different among various soil types, which will influence the sustainable application of RW. It can shed insights into solving the water scarcity issue and improving water sustainability in subtropical regions.

Factors influencing groundwater behaviour and performance of groundwater-based water supply schemes in rural India

ABSTRACT This study investigates the factors influencing groundwater behaviour during the monsoon using data on rainfall, pre-monsoon depth of the water levels, groundwater level fluctuations, aquifer specific yield, and soil infiltration characteristics. It shows the effect of pre-monsoon depth of the water levels along with rainfall, soil infiltration and specific yield in controlling recharge during the monsoon. It also explores the factors influencing the performance of drinking water schemes. It shows that the intensity of irrigation demand, extent of gravity-based surface irrigation, aquifer storage space, and the aquifer recharge potential are important determinants for the sustainability of the groundwater-based drinking water schemes.

Effect of raindrop splashes on topsoil structure and infiltration characteristics

Raindrop splashing causes pore blockage in topsoil and reduces its infiltration capacity. In this study, simulated rainfall and infiltration tests were used to analyze the relationship between differences in the topsoil structure and the infiltration capacity of Lou soil on the Loess Plateau under different raindrop splashing conditions. The results show that, compared with soil existing under no raindrop splashing, the structure of the disturbed topsoil was altered, and the number of aggregates (A) and the three-dimensional fractal dimension (FD) degree were significantly increased (P < 0.05). At the same time, the pore volume (VP) and macroporosity (PL) were significantly reduced (P < 0.05). Aggregates splashed by 4.05 mm diameter raindrops were the most severely disturbed, and the pore clogging rate (CR) reached as high as 46.40%. After the broken aggregates blocked the pores, a dense and low permeable crust was formed on the topsoil, and it decreased the cumulative amount of infiltration and the infiltration rate. With increasing splash frequencies and raindrop diameters, the topsoil infiltration rate decreased gradually, and the soil infiltration reduction effect (IR) increased significantly. Three splashes later, the IR effect reached 94.21%. The study reveals the processes and mechanisms driving changes in soil infiltration characteristics from the perspective of changes in topsoil structure caused by raindrop splashing.

Evaluation of Seasonal Effects of Tillage and Drainage Management Practices on Soil Physical Properties and Infiltration Characteristics in a Silt-Loam Soil

The impacts of tillage and drainage managements on soil infiltration characteristics need to be scrutinized for a better understanding and prediction of soil hydrological processes, such as runoff, evapotranspration and soil water storage. The objectives of this study were i) to evaluate the effects of tillage and drainage practices on soil physical properties and water infiltration, and ii) to compare prediction accuracy of estimated and optimized infiltration model characteristics for the observed and predicted quantities of infiltration process in the soil. The research site contains the Crosby-Kokomo soil series (fine, mixed, mesic, Aeric Ochraqualf and fine, mixed, mesic Typic Argiaquoll, respectively). The experiment was a two factorial completely randomized block design with two levels of tillage (chisel plow (CH) and no-till (NT)) and two levels of drainage (drained (D) and undrained (UD)) with three replicates. Soil bulk density (ρb), saturated hydraulic conductivity (Ksat), soil moisture retention curves (SMRC), soil infiltration capacity and piezometric water head in each treatment were also measured. Soil drainage flows at each drain lateral and outlet discharges were measured. The results showed that The UD treatments were always higher for Ksat values than the D treatments regardless of the tillage practices for both depths and the CH treatments always had greater Ksat values than those in the NT at both the depths regardless of drainage practices. The D treatments reduced the soil bulk density by 4.2 and 0.8 % in the surface soil and 4.61 and 6.7% for the subsurface soil in respect to no-till-UD and chisel-UD treatments. The UD treatments had higher bulk density at both of the depths than those of the D treatments regardless of tillage practices except the CH-UD treatments. The NT had higher bulk density at both depths of the soil than those of the CH treatments regardless of drainage practices. Drainage increased pore size distribution significantly higher than the UD treatments (p<0.05). The D treatments had significantly higher storage pores and effective pores (9.37%) (pores retaining water at -10kPa pressure head) than the ones in the UD treatments (8.96%) (p<0.05). The NT treatments yielded higher infiltration rates than the CH and the D treatments produced higher apparent infiltration rates and cumulative infiltration values than the UDs. The changes in soil physical properties were found to be strongly and significantly dependent on season, soil depth, and rainfall (p<0.05). The optimized infiltration models predicted larger range of infiltration rate values for each treatment than the estimated infiltration models, indicating that the optimization produced higher accuracy and validity of the predicted models in the field. To conclude, soil dry bulk density, soil saturated hydraulic conductivity, and increased macropore volumes can significantly impact soil hydrological responses to soil water infiltration, soil water storage and drainage flow under conservation tillage and drainage management practices on a seasonal basis. This impact enhances greater potential to capture water in soil for future crop use in the study site.

Modelling and Digital Mapping of the Infiltration Characteristics of Major Agricultural Soils

Modelling and Digital Mapping of the Infiltration Characteristics of Major Agricultural Soils

Soil infiltration characteristics and pore distribution under freezing–thawing conditions

Abstract. Frozen soil infiltration widely occurs in hydrological processes such as seasonal soil freezing and thawing, snowmelt infiltration, and runoff. Accurate measurement and simulation of parameters related to frozen soil infiltration processes are highly important for agricultural water management, environmental issues, and engineering problems in cold regions. Temperature changes cause soil pore size distribution variations and consequently dynamic infiltration capacity changes during different freeze–thaw periods. To better understand these complex processes and to reveal the freeze–thaw action effects on soil pore distribution and infiltration capacity, black soils, meadow soils, and chernozem were selected as test subjects. These soil types account for the largest arable land area in Heilongjiang Province, China. Laboratory tests of soils at different temperatures were conducted using a tension infiltrometer and ethylene glycol aqueous solution. The stable infiltration rate and hydraulic conductivity were measured, and the soil pore distribution was calculated. The results indicated that for the different soil types, macropores, which constituted approximately 0.1 % to 0.2 % of the soil volume under unfrozen conditions, contributed approximately 50 % of the saturated flow, and after soil freezing, the soil macropore proportion decreased to 0.05 % to 0.1 %, while the saturated flow proportion decreased to approximately 30 %. Soil moisture froze into ice crystals inside relatively large pores, resulting in numerous smaller-sized pores, which reduced the number of macropores but increased the number of smaller-sized mesopores, so that the frozen soil infiltration capacity was no longer solely dependent on the macropores. After the ice crystals had melted, more pores were formed within the soil, enhancing the soil permeability.

Behaviors of rainfall infiltration and drainage characteristics of unsaturated soils under relatively high suction state

Behaviors of rainfall infiltration and drainage characteristics of unsaturated soils under relatively high suction state

Effects of ionized brackish water and polyacrylamide application on infiltration characteristics and improving water retention and reducing soil salinity

There is an urgent need for brackish groundwater-based irrigation methods to be developed for saline soils that are effective, economically advantageous, and environmentally friendly. The use of both ionized brackish water and polyacrylamide (PAM) might provide such a method. The long-term use of brackish water irrigation can lead to the secondary salinization of soil and, as a consequence, restrict the development of the agricultural economy. Here, we conducted one-dimensional vertical infiltration experiments to examine the effects of ionized brackish water and PAM on soil infiltration characteristics. The result indicated that the water retention of soil first increased and then decreased with the increased in PAM application rates. The maximum water retention of soil was obtained in PAM application of 0.04% for ionized brackish water treatment. Soil water storage for the 0.04% PAM application under ionized brackish water irrigation was the highest and 5.1% higher compared with non-ionized brackish water at a PAM application rate of 0.04%. The ionized brackish water treatment at a PAM application rate of 0.04% improved the desalinization efficiency by 2.3% compared with non-ionized brackish water treatment. Thus, ionized treatment and PAM application are effective for improving the characteristics of soil water and salt transport and permit the safe use of brackish groundwater for irrigation.