Water Retention Characteristic Curve Research Articles

Impact of natural biochar on soil water retention capacity and quinoa plant growth in different soil textures

Although data regarding the effect of different types of synthetic biochar on plant performance and physical and chemical characteristics of soil is widely available, the effect of natural biochar in this respect is not well known, so far. The purpose of this research was to investigate the effect of 650-million-years old natural biochar at three application levels of 0 %, 2.5 % and 5 % by weight on yield parameters of quinoa plant and the soil water retention characteristic curve in sandy loam, loam, and clay textural classes. The results showed that the application of 5 % natural biochar to the loam soil increased the thousand seed weight by 8 %, but adding 2.5 % of biochar to the sandy loam soil increased biological yield by 2 %, and in loam soil increased root volume by 409 %, compared to the control. The results of the physical parameters of the soil showed that the application of biochar in three soil textures caused an increase in moisture content at the field capacity (1.8 %-11.22 %), a decrease in macropores in the range of 10–46 %, and an increase in micropores in the range of 0.2–10 % in three soil textures. Therefore, it can be concluded that the potential of natural biochar storage affected the physical properties of the soil and increased soil water retention while improving important soil functions.

Pore Size Distribution Derived from Soil–Water Retention Characteristic Curve as Affected by Tillage Intensity

Tillage practices can influence the pore size distribution (PSD) of the soil, affecting soil physical and hydraulic properties as well as processes that are essential for plant growth, soil hydrology, environmental studies and modeling. A study was conducted to assess the effect of no-tillage (NT) and conventional tillage (CT) on PSD derived from soil–water retention curves (SWRCs) using the van Genuchten’s equation (vG) at 0–15 cm and 15–30 cm depths in a sandy loam soil. Values of PSD or slopes (C(h)) were calculated from the SWRCs by differentiating the vG equation. Soil water retention curves under both tillage systems and within two depths were determined using the evaporation HYPROP method. The vG equation was well fitted to measured soil water retention data. The diameter (D) of soil pores retaining water at various matric suctions (|h|) of water in soils was calculated by the capillary equation. A significant effect of tillage on soil PSD was observed in the macro-pore (D > 1000 μm, at |h| < 3 hPa) and meso-pore (D between 10 and 1000 μm, at |h| between 300 and 3 hPa) size classes, while the micro-pores size class (D < 10 μm, at |h| > 300 hPa) was unaffected at the 0–15 and 15–30 cm depths. Larger values of C(h) or PSD in CT were associated with greater soil loosening induced by the CT operations and greater proportion of large pores (structural porosity) occurred in soils under CT compared to soils under NT. Macro-pore and meso-pore proportions were significantly greater in soils under CT than in soils under NT within both soil depths. The hydraulic parameters of the vG equation and its derivative function can be used to compare soil–water retention curves and pore size distributions between soils under untilled and tilled conditions.

An appraisal on the soil wetting water retention characteristic curve determined from mini disk infiltrometer and sensor measurements

An appraisal on the soil wetting water retention characteristic curve determined from mini disk infiltrometer and sensor measurements

Soil hydrologic properties in permanent raised beds—A field study experiment on wheat–maize cropping systems

AbstractPermanent raised beds (PRB) are widely applied in agriculture around the World and have proven to be an excellent option for crops (wheat, maize, etc.). In particular, they have the potential to conserve soil and water resources in agricultural production globally. Many researchers are studying the effects of PRB on soil chemical properties (N, P, K, and SOC), plant growth characteristics, and water use efficiency in different regions. However, few experiments have investigated the soil's hydraulic performance. In this study, a 6‐year field experiment was conducted under a maize–wheat rotation cropping system in North China Plain (NCP). The effects on the soil's hydraulic properties of no‐tillage (NT) and traditional tillage (TT) on flat fields and no‐till PRB treatments were assessed. Specifically, nine soil samples were collected at 0–15 cm depth and 15–30 cm depth to assess the soil's hydraulic performance. The results showed that the total porosity under PRB (42.1%, 15–30 cm) was significantly improved by 13.5% compared to TT (37.1%, 15–30 cm). The soil organic carbon under PRB (8.65%, 15–30 cm) was increased by 13.82% compared to TT (7.6%, 15–30 cm). Changes in the slope (b) of the soil water retention characteristic curve under the PRB (7.2, 15–30 cm) treatment were indicative of an improvement in the pore size distribution, increased soil water retention, and greater infiltration rates. In addition, positive changes in lateral water infiltration from furrow irrigation were observed under PRB (over 25 mm min‐1 in 45 min). These improved soil physical parameters demonstrated that PRB can offer more possibilities for water conservation in the field. In addition, the application of PRB and the principles of conservation agriculture have potential for the effective of water use efficiency and for improving the quality of soil.

Physical and hydrological characteristics and modelling of the soil water retention curve in the brazilian semi-arid region

Semiarid regions are characterised by water scarcity, a limiting factor on plant growth and development. The Sertão Canal was built in the semiarid region of Brazil, more specifically in the state of Alagoas, with the aim of making year-round irrigation possible. However, for the best water management, a physical and hydrological knowledge of the soils is necessary. As such, the aim of this study was to determine the physical and hydrological characteristics of three different types of soil (Argisol, Quartzarenic Neossol and Regolithic Neossol) under native vegetation (Caatinga) and agricultural systems in the semiarid region of Alagoas, as well as to adjust the soil water retention characteristic curves. Soil samples were collected at depths of 0-10, 10-20 and 20-30 cm in the municipalities of Inhapi, Delmiro Gouveia and Pariconha, in the state of Alagoas. The points of the moisture characteristic curve were determined by the Richards method, at pressures of 33, 100, 500, 1000 and 1500 kPa. Retention curves were modelled using the exponential decay equation and compared using the van Genuchten equation, modelled with the help of the RETC computer software. Particle size varied according to the textural classification of the different soils, from Sand to a Sandy Clay Loam. The retention curve fluctuated due to the particle size of the soil, with the Red-Yellow Argisol (Inhapi) having a greater capacity for water retention. Extremely sandy soils, such as those in the Delmiro Gouveia region, had a low capacity for retaining water. For each soil sample, the exponential decay equation gave the best fit, with values for R2adjust of greater than 0.93. When the measured soil moisture levels were compared with the levels estimated by the RETC model, some of the treatments were unable to estimate accurately the moisture levels obtained with the soil water retention curves.

Predictive model for water retention curve of water-absorbing polymer amended soil

Water-absorbing polymer (WAP) amendment is emerging as a sustainable soil management technique in various geoenvironmental projects for controlling the subsurface water flow in the vadose zone. The addition of WAP can alter the pore structure and improve water-retention characteristics of the soil. The existing water-retention characteristic curve (WRCC) models for polymer-amended soils are complex and require a number of empirical parameters, which cannot be easily obtained through simple laboratory experimentation. The current study proposes a simple predictive WRCC model for WAP-amended soils based on the understanding that WAP particles absorb and retain water within their polymer structure and therefore influence the void ratio. The proposed model captures the change in the void ratio of the amended soil through a modified phase relationship for predicting WRCC. The performance of the model was validated for four different textured soils with varying WAP concentrations. The comparison between measured and predicted WRCC indicates that the proposed model can capture the changes in the void ratio as well as the WRCC with adequate accuracy.

Analysis of Loess Wet Deformation and Slope Stability under Rainfall Conditions

Loess is a typical unsaturated soil, and the unsaturated strength is the basis for the analysis and evaluation of engineering stability in the loess area. Based on the analysis of the wet load deformation strength, rainwater infiltration and slope stability of unsaturated loess, this paper obtains the yield stress under different suction caused by soil humidification at different depths, the water retention characteristic curve and the different loess with different dry-wet cycle history. The research conclusions can provide reference for the construction of loess collapsibility model and the numerical calculation of the collapsibility deformation of the loess site under the infiltration of rainwater.

Modeling of soil water retention based on 3D micro-tomographic image analysis

This paper proposes the use of an algorithm based on the mercury intrusion porosimetry (MIP) method to obtain the water retention characteristic curve (pF curve) of a soil under different treatments. 3D X-ray micro-tomographic images were used to quantify pore size distribution, which was employed for the evaluation of the water retention in different matric potentials. The results showed very good agreement between the traditional method (obtained by suction tables) and that one based on the MIP algorithm. It means that the use of simulation procedures can be an interesting alternative for the measurement of soil water retention properties.

Quantifying the interactive effect of water absorbing polymer (WAP)-soil texture on plant available water content and irrigation frequency

Past decades have witnessed the impact of climate change resulting in extreme drought conditions, which necessitates innovative and sustainable approaches to enhance water use efficiency. Water absorbing polymers (WAP) are chemically cross-linked structures capable of absorbing and storing huge quantities of water within its three-dimensional network. Due to high water absorbency, these polymers are used for improving the water retention characteristics (WRC) of the soil during drought conditions. For this purpose, it is important to quantify the interactive effect of water absorbency of WAP and soil texture on water use efficiency. This study investigated the effect of WAP amendment on the drying water retention characteristic curve (WRCC) of three different textured soils. The study proved that the inter pore space of a fine-textured soil restricted the swelling of WAP to its full capacity. The combined WRCC and microstructural observations of bare and WAP amended soils added to the experimental reasoning for the comparatively low improvement in water absorption capacity (WAC) of fine-textured soil. At the maximum concentration of WAP application, the increase in plant available water content (PAWC) for coarse to fine-textured soil varied from 3.3 to 1.2 times, respectively. This study further demonstrated that the PAWC improvement factor is predominantly texture dependent and can be determined solely from the WRCC of a given soil. An empirical relationship was proposed for estimating PAWC and wilting time improvement factor based on particle size fraction of soil (texture). Based on the empirical models, it was concluded that the variation in wilting time and PAWC improvement factor was minimal for soils with clay content and fine content exceeding 30% and 60%, respectively. Based on the irrigation water requirement, the optimum WAP application rate for coarse-textured soils (sand, silt loam) was 0.1% while for fine-textured soil (clay loam) the application rate was 0.2%. The quantification presented in this study suggests the need to develop guidelines for WAP application by considering the soil texture to ensure optimal irrigation during drought condition.

Effect of Fines Content on the Hysteretic Behavior of Water-Retention Characteristic Curves of Reconstituted Soils

AbstractAn experimental investigation was carried out to evaluate the influence of fines content on the hysteretic behavior of water-retention characteristic curves (WRCCs) of reconstituted soil su...

Water retention characteristics of iron ore fines

Evaluations of water retention characteristics of typical iron ore fines (IOF) were presented, which was part of experimental works for the estimation of liquefaction potential of IOF heaps. The water retention tests were conducted in a suction range from 0.1 to 106kPa on two IOFs and two artificial soils with various testing techniques. It is observed that water retention characteristic curves of one IOF (IOF-B) converge in terms of the relationship between suction (S) and water content (w) regardless densities of specimens when S exceeds a threshold value (Sth). Based on this finding, water retention characteristics are divided into density and materials affected zones. It is also found that IOFs generally have higher water retention ability than the two artificial soils, from which discussion is made on the effect of specific surface area and mineralogy on water retention characteristics of IOF. Finally, water retention characteristics are linked to compaction curves, from which, with the consideration that degree of saturation at peaks of compaction curves is relatively constant, a safety margin of a recently proposed regulation for maritime transportation of IOF is discussed.

A study on the geotechnical characterization and water retention characteristic curve of pond ash.

The understanding of the engineering behaviour of unsaturated soil is totally dependent on the water retention characteristic curve (WRCC). In this paper, a comprehensive study of the WRCCs of pond ash along with the ash's geotechnical behaviour has been made. The WRCC has been drawn experimentally using a Fredlund device based upon the pressure plate technique for both wetting and drying cycles. Further, an investigation was carried out to study WRCC hysteresis of pond ash. There exists a considerable hysteresis in drying and wetting curves of pond ash sample. The different WRCC models were used to fit the experimental WRCC data. The effect of compaction on WRCC was also studied. The air entry value in the case of a loose sample is low and the sample gets nearly desaturated at low soil suction as compared to a dense sample. Also, the wetting WRCC is predicted using the Feng and Fredlund model as it is difficult and time consuming to measure the whole hysteresis. The predicted results are compared with the measured wetting WRCC. Since the direct measurement of unsaturated hydraulic conductivity is difficult to obtain in engineering practices, the unsaturated hydraulic conductivity function is predicted using the measured WRCC as the input parameter using SEEP/W software.

Uncertainty Quantification in Water Retention Characteristic Curve of Fly Ash Using Copulas

Abstract Water retention characteristic curve (WRCC) is a primary input for modeling the unsaturated behavior of geomaterials. The inadequacy of measurement methodologies in capturing the measurable range of the suction of geomaterials along with material variability induce uncertainties in the quantification of WRCC. The goal of this study is to demonstrate the usefulness of copulas for quantifying the uncertainties in WRCC attributed to the aforementioned reasons. Four instruments measuring different ranges of suction of four fly ashes were used to generate 54 combinations of measured data that would represent possible cases of data-induced uncertainties. van Genuchten WRCC equation parameters (a and n) were determined for these combinations. Statistical analysis of the parameters determined from the 54 combinations indicates a negative correlation with each other; therefore, they represent a bivariate random vector. Four commonly used copulas, Gaussian, Frank, Plackett, and No. 16, were utilized to construct the bivariate density function of the parameters, among which the Gaussian copula was found to be the best fit. The impact of the copula-based model developed in this study on two important unsaturated functions, the suction stress characteristic curve (SSCC) and hydraulic conductivity function (HCF) of fly ash, was investigated and found to be significant. The dispersion in SSCC ranges from monotonically increasing to sharp post peak reduction in the suction range of 20–50 kPa. The limiting state of suction required to reach the theoretical minimum permeability was found to vary widely in the range of 300–9,000 kPa. The study shows that a Gaussian copula with lognormal marginals can adequately capture the significant range of uncertainties associated with WRCC.

Comparison of air entry values from soil water retention and volumetric shrinkage characteristic curves

The soil water retention curve (SWRC) is the relationship between the volumetric water content and the matric suction of an unsaturated soil. One key parameter of the SWRC is the air-entry value (AEV), which defines the minimum matric suction at which air starts to enter the largest pores in the soil as it desaturates. The volumetric water content at the AEV can also be identified from the evolution of the volumetric shrinkage characteristic curve (VSCC). The VSCC is the relationship between the void ratio and volumetric water content of an unsaturated soil as it dries towards the shrinkage limit. Fine-grained materials, such as dredged materials and mine tailings comprising clay minerals and natural clays, show a marked volume change with variation of the water content. In this study, the AEVs of three fine-grained materials (dredged material, red mud and kaolin) were measured from SWRCs and compared with the shrinkage limit values obtained from the corresponding VSCCs. The SWRC was measured by utilizing full-range polymer tensiometers. The polymer tensiometer is filled with polymer solution instead of water, diminishing the effect of soil salinity, and can measure the matric suction up to -1500 kPa. The SWRC and VSCC results were compared and discussed in terms of their applicability to providing an understanding of unsaturated soils that undergoing large volume change.

A unified constitutive model for unsaturated soil under monotonic and cyclic loading

This study presents a sophisticated elastoplastic constitutive model for unsaturated soil using Bishop-type skeleton stress and degree of saturation as state variables in the framework of critical state soil mechanism. The model is proposed in order to describe the coupled hydromechanical behavior of unsaturated soil irrespective of what kind of the loadings or the drainage conditions may be. At the same time, a water retention characteristic curve considering the influence of deformation on degree of saturation is also proposed. In the model, the superloading and subloading concepts are introduced to consider the influences of overconsolidation and structure on deformation and strength of soils. The proposed model only employs nine parameters, among which five parameters are the same as those used in Cam-Clay model. The other four parameters have the clear physical meanings and can be easily determined by conventional soil tests. The capability and accuracy of the proposed model have been validated carefully through a series of laboratory tests such as isotropic loading tests and triaxial monotonic and cyclic compression tests under different mechanical and hydraulic conditions.

Soil quality attributes induced by land use changes in the Fincha’a watershed, Nile Basin of western Ethiopia

The success of soil management to maintain soil quality depends on an understanding of how soils respond to land use and practices over time. As a result, the important soil quality indicators were investigated under two land use systems to provide base line data for future research in the Fincha’a Valley Sugar Estate (FVSE), within the Nile basin of Western Ethiopia. The evidences provided by this study indicated that land use changes caused changes on soil bulk density (ρb), soil water content, Particle size distribution (sand, silt and clay), soil pH, electrical conductivity (EC), soil organic matter (SOM), total N, carbon to nitrogen ratio (C:N) and available phosphorous (Av. P). The study revealed that soil organic matter (SOM), sand content and total N decreased with increase in soil depth. While bulk density (ρb), EC and clay content increased with soil depth. Particle size distribution (sand, silt, and clay) varied with land use, soil depth and soil type. Particle size distribution was changed from Sandy clay to clay due to land use change. Bulk density (ρb), EC, soil organic matter (SOM) and C:N varied significantly (P<0.01, P<0.05), respectively, with land use and soil depth. Land use changes caused bulk density (ρb) to be increased. The study indicated that soil pH was higher in irrigated land than the un irrigated land. This attributed to the transportation of soluble cations from the upstream to the downstream irrigated land by water soil erosion. The different soil fertility management practices also contributed to the variation. On the other hands, soil organic matter (SOM) and total N were lower in irrigated land. Relatively, the lower soil organic matter (SOM) and total N contents in irrigated land attributed to the optimum soil moisture content throughout the year that created favorable environmental condition for SOM decomposition. The study also revealed that soil management groups and soil water holding capacity at field capacity and permanent wilting point were affected by irrigation (land use).It was identified more than 50% of the soil quality indicators increased with depth. This might be the influence of irrigation water in accelerating leaching process. The main degradation process overcome the study area was waterlogging and soil compaction. The irrigation development in the area requires improved drainage network and proper land management. Therefore, reducing the intensive mechanized tillage practices and use of integrated inorganic and organic fertilizers could replenish the degraded soil quality for sustainable agricultural production in the study area. It is therefore, suggested that appropriate and integrated land management options for different land use systems together with identification of soil management groups and water retention characteristic curves are required to sustain agricultural productivity while protecting the environmental degradation. Keywords : Soil Quality Land Use Soil Type Environment Sugarcane Land Management Fincha’a Valley Western Ethiopia Fertilizers

Probabilistic Analysis of Water Retention Characteristic Curve of Fly Ash

Probabilistic Analysis of Water Retention Characteristic Curve of Fly Ash

Evaluation of Measurement Methodologies Used for Establishing Water Retention Characteristic Curve of Fly Ash

AbstractFly ash (FA) has potential applications in geotechnical and geoenvironmental projects, where its water retention characteristic curve (WRCC) is important. The main objective of this study was to establish the inherent range of measured suction of FAs using four different tools: tensiometer (TM), matric potential sensor, equitensiometer (EQT), and WP4 dew point potentiameter with a varying measurement range. Based on the measured results, the variability of WRCC equation parameters of four FAs collected from different thermal power plants were studied. Further, the sensitivity of a different range of measured suction on WRCC equation parameters of FA was investigated. The study indicated that the possible range of measurable suction for FA is 1 to 1000 kPa, which can be measured conveniently with an EQT. The parameters of FA were not influenced by high suction measurements (&amp;gt;1000 kPa) of WP4. The suction data (&amp;gt;1000 kPa) obtained using the WP4 can be appended with a low-suction-range instrument such as a TM for a better representation of the WRCC of FA. However, the study indicated that WRCC parameterization of FA is influenced more by the low range of suction.

Evaluation of Different Laboratory Procedures for Determining Suction–Water Content Relationship of Cohesionless Geomaterials

AbstractThe determination of suction–water content relationship (SWR) is of prime importance in unsaturated soil mechanics. When such a relationship is obtained from continuous drying or wetting process of the same soil sample, it is termed as water retention characteristic curve (WRCC). The relationship obtained from suction measurement of remolded soil samples with different water content is termed as spot SWR (SSWR). Most of the reported studies use drying WRCC (DWRCC) because of the relative ease of its measurement as compared to wetting WRCC (WWRCC). There are not many studies that critically compare measured DWRCC, WWRCC, and SSWR of soils. Such a comparison would help to understand the differences in WRCC attributable to hysteresis and limitations of spot measurements, if any. A simple procedure similar to the field wetting process is discussed in this paper for developing DWRCC and WWRCC on the same soil sample, one after the other. WRCCs and SSWRs of three cohesionless soils are not unique for th...

Influence of simulated traffic and roots of turfgrass species on soil pore characteristics

A field experiment was conducted during the period of 2011 to 2012 to study the effect of traffic on physical properties of soil when different turfgrass species were cultivated. Experimental plots were established with three replications in a split-plot design with species as a main plot and traffic treatment as a subplot. The traffic treatment was applied to the turfgrass using Brinkman traffic simulator (BTS). Two levels of treatments were applied: non-trafficked vs. trafficked. Four grass species were used, Festuca arundinacea, Festuca rubra, Poa pratensis and Lolium perenne. The BTS compaction was applied every week since the beginning of April to the end of November. Physical parameters of soil, bulk density, total porosity and penetration resistance were determined. Based on the water retention characteristic curve, the pore size distribution, available water content (AWC), productive water content (PWC) and relative water capacity (RWC) were calculated. Root parameters like length density (RLD) and dry matter (RDM) were determined as well.Both experimental factors, grass species and BTS compaction, changed soil physical parameters, penetration resistance, bulk density and total porosity. These changes were results of modification of pore system. Large pores were modified by grass species and BTS compaction. However, storage pores of 0.5–50μm in diameter were affected only by grass roots. This reflected in the water retention characteristics of the soil. The RWC ratio indicated poor water conditions prevailing in the soil except trafficked two grass species, namely F. arundinacea and L. perenne. The highest water retention in the range of the AWC was noticed for F. arundinacea (0.191cm3cm−3) and for L. perenne (0.187cm3cm−3). Significantly lower AWC was recorded for F. rubra and P. pratensis, 0.151 and 0.141cm3cm−3, respectively. The similar relationship was also observed for the PWC. It was found that changes in the AWC and PWC can be explained by the root parameters. The higher root biomass concentration in the soil had a beneficial effect on the soil water retention. It can be concluded that F. arundinacea and L. perenne can be recommended for turfgrasses with irrigation system where the water resources are limited.