Low Water Retention Research Articles

Liquid absorbent bamboo fiber foams: Towards 100% ligno-cellulosic menstrual absorbent pads

Traditional menstrual absorbent pads typically combine cellulose fiber fluff pulp with non-biodegradable, petroleum-based superabsorbent polymers (SAPs). To eliminate the need for SAPs, this study explores foaming as a method to create a highly porous lignocellulosic fiber network capable of storing large amounts of fluid. Bamboo fibers were chosen due to their high lignin content, which is expected to help maintain the structural integrity of the porous network during liquid absorption and preventing collapse compared to 100% cellulose fibers. The bamboo fiber foams demonstrated remarkable porosity and superior absorbency compared to commercial pads, but they exhibited lower water retention when subjected to compression. Refining the fibers and incorporating microfibrillated cellulose offer promising opportunities to enhance water retention.

Circular economy strategies in sedimentary phosphate mine reclamation: Development of technosol from phosphate waste rock

Proper management of mine waste plays a crucial role in minimizing environmental impacts. One potential solution to tackle this problem involves transforming mine waste rock into soil to facilitate the process of mine restoration. The aim of this study was to assess the mineralogical, chemical, and physical characteristics of technosol derived from phosphate mine waste dumps. Following this evaluation, a novel rehabilitation strategy was proposed. For this purpose, a total of 32 samples were systematically collected across a 4 ha area of technosols, which had been established in accordance with the waste rock soil rehabilitation strategy involving geomorphic reshaping. According to the findings, phosphate mining left the soil with a sandy texture, resulting in a degraded soil structure with severely unfavorable crop growth conditions, notably poor stability, and low water retention. The chemistry of the studied soils was characterized by the dominance of CaO (29.02 wt%± 1.01) > SiO2 (27.61 wt% ± 0.61) > P2O5 (11.34 wt% ± 0.23) > MgO (5.97 wt%±0.16). Mineralogically, the samples were mainly formed by quartz, dolomite, calcite, apatite, and clay minerals. The prevalence of dolomite played a significant role in enhancing the accessibility of Mg as an essential nutrient and the occurrence of apatite in the soil resulted in the presence of P2O5. However, the abundance of Ca was linked to three major minerals: calcite, apatite, and dolomite. X-ray fluorescence analyses demonstrated that the concentrations of Fe2O3, K2O, and SO3 did not exceed 2 wt%.Organic matter, represented by SOC <0.2% and N < 0.02%, demonstrated an extraordinary deficiency in the study area. The analysis of element bioavailability confirmed that the soil was rich in Ca (10383,26 mg/kg), Mg (278,47 mg/kg), Zn (12,82 mg/kg), and Cu (3,7 mg/kg) but deficient in other essential nutrients such as P, K, S, Mn, and Fe. Our research results provide a set of recommendations aimed at enhancing existing mine rehabilitation practices applicable to both pre- and post-rehabilitation phases, leveraging automated mineralogy and circular economy principles. Notably, we propose a rehabilitation strategy to be implemented prior to the geomorphic reshaping phase, which is intended to reduce costs and efforts associated with soil reconstitution.

Incorporation of mixed strawberry and acerola jam into Greek-style goat yogurt with autochthonous adjunct culture of Limosilactobacillus mucosae CNPC007: Impact on technological, nutritional, bioactive, and microbiological properties

This study aimed to assess the impact of adding strawberry and acerola jam, along with Limosilactobacillus mucosae CNPC007, on the technological, nutritional, bioactive, and microbiological properties of Greek-style goat yogurt. Six yogurt formulations were developed: without and with the addition of L. mucosae CNPC007 (CY and PY, respectively), and with 10 % and 15 % jam (CY10, CY15, PY10, and PY15, respectively). The inclusion of jam enriched the yogurt with phenolic compounds and significantly enhanced antioxidant activity, as measured by FRAP and ABTS assays. The highest values were observed after 28 days of storage in the PY15 formulation (0.177 ± 0.01 and 3.43 ± 0.01 µmol TEAC/g, respectively), compared to CY (0.013 ± 0.01 and 0.19 ± 0.01 µmol TEAC/g, respectively) and PY (0.010 ± 0.01 and 0.23 ± 0.01 µmol TEAC/g, respectively). This increase was likely driven by the presence of anthocyanins and flavonoids in the jam, as indicated by heatmap correlation analysis. DPI and EPI were also influenced by the addition of jam and L. mucosae CNPC007, with EPI increasing in the PY10 and PY15 formulations, reaching approximately 40 % after 28 days. The incorporation of jam resulted in a decrease in the L* (<90) and an increase in the b* (>14) color parameters. Additionally, jam-enriched formulations exhibited higher syneresis and lower water retention capacity (WRC) throughout storage compared to control formulations, with average syneresis exceeding 26 % and WRC falling below 75 % after 28 days. In general, all yogurt formulations showed a reduction in lactose, an increase in glucose and galactose, and the production of lactic acid during storage. The lower lactose content observed after 28 days of storage in the PY (0.84 ± 0.01 g/100 g), PY10 (0.82 ± 0.01 g/100 g), and PY15 (0.98 ± 0.01 g/100 g) formulations indicates active sugar metabolism by L. mucosae CNPC007. All formulations met microbiological safety standards, confirming their suitability for consumption. Formulations containing L. mucosae CNPC007 showed viable cell counts exceeding the minimum recommended to produce health benefits (>7 log CFU/g) throughout the 28-day refrigerated storage and after in vitro digestion. These findings underscore the potential of combining tropical fruit jams with probiotics to develop a multifunctional, value-added yogurt product that delivers substantial health benefits to consumers.

Effect of Three Different Types of Biochar on Bioelectricity Generated from Plant Microbial Fuel Cells under Unsaturated Soil Condition.

Plant microbial fuel cell (PMFC) is an emerging technology, showing promise for environmental biosensors and sustainable energy production. Despite its potential, PMFCs struggle with issues like low power output and limited drought resistance. Recent studies proposed that integrating biochar may enhance PMFC performance due to its physicochemical properties. The influence of different biochar types on PMFC efficiency has been minimally explored. This study aims to fill this gap by evaluating the performance of PMFCs integrated with various biochar types under unsaturated soil conditions. The study found that the addition of biochar types─specifically reed straw biochar (RSB), apple wood biochar (AWB), and corn straw biochar (CSB)─significantly influenced the performance of PMFCs. RSB, with its large surface area and porous structure, notably increased the current output by reducing soil resistance and enhancing electron transfer efficiency in microbial reduction reactions, achieving a peak power density of approximately 1608 mW/m2. AWB, despite its less porous structure, leveraged its high cation exchange capacity and hydrophilic functional groups to foster microbial community growth and diversity, thereby also increasing bioelectricity output. Conversely, CSB, with its large surface area, showed the least improvement in PMFC performance due to its layered structure and lower water retention capacity. Additionally, under drought conditions, PMFCs with added RSB and AWB exhibited better drought resistance due to their ability to improve soil moisture characteristics and enhance soil conductivity. The addition of biochar reduced soil resistance, increasing the bioelectric output of PMFCs and maintaining good performance even under low moisture conditions. This study highlights the critical role of biochar's surface area and functional groups in optimizing PMFC performance. It enhances our understanding of PMFC optimization and might offer a novel power generation method for the future, while also presenting a fresh strategy for soil monitoring.

Optimizing Glutinous Corn Productivity through Demonstration Plots with the Application of Combined Organic Ameliorants

Sandy soil in Muncuk Karya, Ampenan, has low water retention and nutrient content, making it difficult for sticky rice farmers to meet their plants' water and nutrient needs. To overcome this challenge, research entitled "Optimizing Glutinous Corn Productivity through Demonstration Plots with the Application of Combined Organic Ameliorants" was carried out using an experimental methodology using a randomized block design involving five treatments and four replications, so that there were a total of 20 treatment plots. The treatments applied consisted of: A1 (50% cow manure + 50% mycorrhizal biofertilizer), A2 (50% compost + 50% mycorrhizal biofertilizer), A3 (50% fertile organic fertilizer + 50% mycorrhizal biofertilizer), A4 (50% rice husk charcoal + 50% mycorrhizal biofertilizer), and A5 (50% mixture of cow manure, compost, fertile organic fertilizer, and rice husk charcoal with a volume ratio of 1:1:1:1 + 50% mycorrhizal biofertilizer). The research results showed that the application of ameliorant, a combination of 50% cow manure and 50% mycorrhizal biofertilizer, was proven to be effective in increasing growth, plant productivity, soil nutrient concentration, plant nutrient uptake, and mycorrhizal development in the soil. To increase the productivity of sticky corn plants, soil fertility, plant nutrient uptake, and mycorrhiza development, it is recommended to use this combination ameliorant application.

Biomimetic kartogenin containing κ-carrageenan hydrogel for nucleus pulposus regeneration

Intervertebral disc degeneration is a clinical disease that reduces the quality of patient's life. The degeneration usually initiates in the nucleus pulposus (NP), hence the use of hydrogels represents a promising therapeutic approach. However, the viscoelastic nature of hydrogel and its ability to provide biomimetic architecture and biochemical cues influence the regeneration capability. This study focused on tuning the physical nature of a glycosaminoglycan hydrogel (κ-carrageenan) as well as the release kinetics of a chondrogenic factor (kartogenin - KGN) through physical cross-linking. For this, κ-carrageenan was cross linked with 2.5 % and 5 % potassium chloride (KCl) for 15 and 30 min and loaded with KGN molecule at 50 μM and 100 μM. The tight network structure with low water retention and degradation property was seen in hydrogel cross-linked with increased KCl concentration and time. However, optimal degradation along with NP mimicking viscoelastic nature was exhibited by 5 wt% KCl treated hydrogel (H3 hydrogel). All hydrogel groups exhibited burst KGN release at 24 h followed by a sustained release for 5 days. However, hydrogel cross-linked with 5 wt% KCl enhanced chondrogenic differentiation, mainly at lower KGN dose. In summary, this study shows the potential application of biomimetic KGN laden carrageenan hydrogel in NP regeneration.

Effect of javanese grasshopper (Valanga nigricornis Burm.) flour on chicken sausage physical properties and its microstructure

Abstract Chicken is rich in protein, but it lacks mineral content. The use of edible insects to enrich the nutritional value, especially the mineral content, of processed chicken-based products such as chicken sausages can also affect their physical quality. The effect of edible insects on chicken sausages is rarely studied and needs further investigation. The purpose of this study was to fortify chicken sausage with Javanese grasshopper flour (Valanga nigricornis Burm.) and evaluate its physical properties. The experimental design employed a completely randomized design (CRD), with the following factors: levels of Javanese grasshopper flour (GF), including a control without GF (F0); 15% GF (F1); 10% GF (F2); and 5% GF (F3), each level was tested in triplicate. Physical properties, namely water holding capacity (WHC), pH, color, texture profile, and microstructure under scanning electron microscope (SEM), were measured. The results demonstrated that formulating chicken sausages with Javanese grasshopper flour significantly altered the physical properties and texture profile. Javanese grasshopper-fortified sausages exhibited low water retention, darker color, softer texture, and irregular aggregate microstructures. This study concludes that Javanese grasshopper flour can be utilized to fortify chicken sausages, resulting in 52.0-167.7% increase in water holding capacity, 5.1-37.9% decrease in hardness, and darker appearance expressed in lower L value by 7.6-24.7%.

Impact of starch amylose and amylopectin on the rheological and 3D printing properties of corn starch

This study evaluated the influence of the amylose and amylopectin on the physicochemical properties and printing performance of corn starch gels. Amylose in starch-based gels enhances their storage modulus and the support performance of printed products by promoting the formation of cross-linked gel structures and crystalline structures. However, the higher amylose content in starch gels makes extrusion difficult, resulting in intermittent extrusion in 3D printing. Despite the increased shear-thinning ability of high-amylose starch, its low water retention capacity leads to water loss and rough printed morphology. Additionally, starch with 72 % amylose content exhibits insufficient adhesive properties for effective layer bonding, negatively impacting structural integrity. While gels with 72 % and 56 % amylose content demonstrate higher viscosity and enhanced mechanical properties, their poor adhesion limits the quality of printed layers. Conversely, waxy starch gel demonstrates continuous extrusion and adhesion but lacks adequate support. The 27 % corn starch gel achieves the highest 3D printing accuracy at 88.12 %, suggesting an optimal amylose-amylopectin ratio for desired ink material performance. These findings enhance our understanding of the relationship between amylose content in starch and 3D printing performance, providing a theoretical basis for the development of starch-based printing products.

Forest disturbance thresholds on summer low flows in the interior of British Columbia, Canada

Summer low flows are critically important for community water supply and various aquatic functions in the interior of British Columbia (BC), Canada. There is a critical need to determine forest disturbance thresholds on summer low flows, particularly in the context of climate change and increasing forest disturbance. The forest disturbance threshold is defined as the disturbance level above which significant changes in flow variables are detected. In this study, we developed a seasonal hydrological response curve to determine forest disturbance thresholds for significant hydrological impacts on summer low flows in 20 forested watersheds in the BC interior. Based on the proposed method, the results suggest that forest disturbance thresholds varied from 8 to 52 % of CECA (cumulative equivalent clear-cut area) with an average of 18 %, which were not significantly different from thresholds on annual streamflow. Watersheds characterized by more distinct dry summers, lower annual energy availability, higher snow contributions, larger sizes, and greater topographic gradients (represented by greater slope, elevation difference, and downslope distance gradient, and lower water retention index) had lower disturbance thresholds on summer low flows. Both positive (increasing) and negative (decreasing) impacts of forest disturbance on summer low flows were detected. These results can greatly support practical watershed management for sustaining water supply in the local communities. Our methodology can potentially be applied in any individual watershed to assess forest disturbance thresholds on summer low flows where long-term data on forest disturbance, climate, and hydrology are available.

Sulfonated PEEK-based IPMC actuators: Exploring environmental influences

Ionomeric Polymer-Metal Composites (IPMCs) with a layered metal/polymer/metal structure are innovative biomimetic materials widely used in applications such as actuators, sensors, artificial muscles, and robotics due to their dynamic response to electrical stimuli. Nafion® is commonly used for these applications but is associated with high costs, low water retention, and poor performance at elevated temperatures. To address this, sulfonated poly(ether ether ketone) (SPEEK) is a promising and cost-effective alternative. This study focuses on evaluating the viability of SPEEK in IPMCs under varying environmental conditions, specifically a wide range of relative humidity (RH) levels (30%, 60%, and 90%) and two different counterions (H+ and Li+). FTIR tests confirmed the successful sulfonation of SPEEK, and sulfonation degrees (SD) of 44%, 72%, and 91% were determined by titration. Results indicate that increased SD leads to higher hydration levels, enhancing performance as actuators. Regarding electromechanical performance, SPEEK-based IPMCs demonstrated results comparable or superior to Nafion. Higher RH positively influenced electromechanical performance, increasing displacement and displacement rate values. Additionally, electrochemical/mechanical tests confirmed that, for the H+ counterion, SPEEK exhibited superior performance. In conclusion, SPEEK-based IPMCs, especially with H+ as the counterion, can potentially replace Nafion, offering a cost-effective alternative with favorable electromechanical performance under varying environmental conditions.

SPATIAL VARIABILITY OF SOIL PHYSICAL PROPERTIES IN SOUTHERN MANKAYAN, BENGUET, PHILIPPINES

Abstract. Hydrothermal alteration in the Mankayan Mineral District in Benguet, Philippines, has had a significant impact on the soil characteristics. Thus, soil characterisation in landslide zones offer useful insights on the nature of slope failure and provide baseline data that may be used with susceptibility mapping and hazard zonations. The study elucidated the physical characteristics of the soils in the southern portion of Mankayan and mapped out the spatial distribution in the area. High sand and low clay content cause low slope stability due to the low water retention in soil, low plasticity, and low shear strength of materials while the resulting porosity led to poor drainage. Results show that the soil's physical properties, whereas most rock units have been affected by alteration, have caused rock deterioration that eventually led to slope failures. The presence of various parent material in the study site influenced the distribution of soil physical properties, specifically the influence of dacite on the Atterberg limits in the central area of southern Mankayan.

Host suitability for germination differs from that of later stages of development in a rare epiphytic orchid

We explore phorophyte suitability for germination and establishment of the epiphytic orchid, Psychilis kraenzlinii. We found that the orchid grows on a subset of the available tree species and shows preference for the endemic Machaonia portoricensis (Rubiaceae). The orchid preferred trees with smoother bark with high water holding capacity and low water retention capacity. Microclimatic conditions under which embryos began pre-germination stages mirrored that of the adult orchid, but germination did not, suggesting that suitable germination sites are not necessarily the best sites for later stages of development.

Strong, tough, high-release, and antibacterial nanocellulose hydrogel for refrigerated chicken preservation

Enormous amounts of food resources are annually wasted because of microbial contamination, highlighting the critical role of effective food packaging in preventing such losses. However, traditional food packaging faces several limitations, such as low mechanical strength, poor fatigue resistance, and low water retention. In this study, we aimed to prepare nanocellulose hydrogels with enhanced stretchability, fatigue resistance, high water retention, and antibacterial properties using soy hull nanocellulose (SHNC), polyvinyl alcohol (PVA), sodium alginate (SA), and tannic acid (TA) as raw materials. These hydrogels were applied in food packaging to extend the shelf life of refrigerated chicken. The structure and properties (e.g., mechanical, antibacterial, and barrier properties) of these hydrogels were characterized using different techniques. Fourier-transform infrared spectroscopy revealed the presence of hydrogen and ester bonds in the hydrogels, whereas scanning electron microscopy revealed the three-dimensional network structure of the hydrogels. Mechanical testing demonstrated that the SHNC/PVA/SA/TA-2 hydrogel exhibited excellent tensile properties (elongation = 160 %), viscoelasticity (storage modulus of 1000 Pa), and mechanical strength (compressive strength = 10 kPa; tensile strength = 0.35 MPa). Moreover, under weak acidic and alkaline conditions, the ester bonds of the hydrogel broke down with an increase in pH, improving its swelling and release properties. The SHNC/PVA/SA/TA-2 hydrogel displayed an equilibrium swelling ratio exceeding 300 %, with a release rate of >80 % for the bioactive substance TA. Notably, antibacterial testing showed that the SHNC/PVA/SA/TA-2 hydrogel effectively deactivated Staphylococcus aureus and Escherichia coli, prolonging the shelf life of refrigerated chicken to 10 d. Therefore, the SHNC/PVA/SA/TA hydrogels can be used in food packaging to extend the shelf life of refrigerated meat products. Their cost-effectiveness and simple preparation make them suitable for various applications in the food industry.

Digital monitoring and response surface methodology optimization of wheat bran bleaching by hydrogen peroxide and its incorporation into wheat Flour

What bran contains valuable molecules having high nutritional value. However, the characteristic dark color and the poor functional properties of this material make its use as an ingredient in foods very limited. Thus, to improve its potential application in the food industry, it is important to modify its color and structure by appropriate treatment. The aim of this study was to bleach wheat bran using hydrogen peroxide and optimize the bleaching conditions. Response surface methodology was employed to determine the optimal concentrations of hydrogen peroxide and wheat bran (WB), as well as the process duration required to achieve the best chromatic profile. The optimized conditions successfully eliminated the brown color of the wheat bran, resulting in a final product characterized by a chromatic profile compatible with commercial wheat flour, exhibiting the following values: L* = 78, a* = -2.6, and b* = 18.8. These results were achieved using a hydrogen peroxide concentration of 20 %, a wheat bran concentration of 10 %, and a contact time of 20 min. Under these bleaching conditions at pH 11, the resulting bran exhibited lower water retention capacity and a significantly increased extractability of dry matter in aqueous media, rising from 20 % for the unbleached bran to 90 % for the bleached bran. Additionally, when mixed with wheat flour, the results indicated a uniform color when combining wheat flour with 10 % bleached bran. In contrast, the unbleached wheat bran showed the presence of two colors on the surface of the mixtures, as revealed by digital analysis.

ДОСЛІДЖЕННЯ СТАНУ ҐРУНТІВ РЕКУЛЬТИВОВАНИХ ТЕРИТОРІЙ ПІСЛЯ ВИДОБУВАННЯ ІЛЬМЕНІТУ НА ЖИТОМИРСЬКОМУ ПОЛІССІ

The article investigates the physical and mechanical composition of the soils of reclaimed areas after ilmenite mining in Zhytomyr Polissia, in particular, the granulometric composition and moisture content of the soils of the reclaimed areas of the Irshansk Mining and Processing Plant. It also identifies soil types by their fractional composition. To carry out the research, 7 test areas were laid out: a control area undisturbed by mining, a dump of topsoil, a site after technical reclamation, and 4 sites after biological reclamation. In order to study the dynamics of reclaimed soil restoration, we selected sites reclaimed at different times. To determine the influence of tree species on the effectiveness of reclamation, we studied sites with plantations of Pinus sylvestris and plantations of Pinus sylvestris and Betula pendula reclaimed at the same time. For all the studied areas, we determined the granulometric composition of the soil by wet and sieve methods, and soil moisture content. The results of the study showed that the soils of the reclaimed areas are mostly sandy, sandy loam and clay loam. These soils are characterized by low water retention properties and low nutrient content. The study also indicated a correlation between the topography of the studied plots and moisture levels as well as the content of fine fractions in the soil. The research revealed that soils in the areas disturbed by open-pit mining are undergoing significant transformations, which has a negative impact on their forest vegetation potential. To restore this potential, it is necessary to carry out high-quality technical and biological reclamation using modern advanced methods. To improve the effectiveness of reclamation of disturbed areas, it is beneficial to apply mineral and organic fertilizers, plant nitrogen-fixing plants, and add biochar to the soil fertile layer at the stage of levelling of the area.

Grafting seedling rootstock strengthens tolerance to drought stress in polyploid mulberry (Morus alba L.)

The economically adaptable mulberry (Morus alba L.) has a long history of grafting in China, yet the physiological mechanisms and advantages in drought tolerance remain unexplored. In our study, we investigated the responses of self-rooted 2X (diploid), 3X (triploid), and 4X (tetraploid) plants, as well as polyploid plants grafted onto diploid seedling rootstocks (2X/2X, 3X/2X, and 4X/2X) under drought stress. We found that self-rooted diploid plants exhibited the most severe phenotypic damage, lowest water retention, photosynthetic capacity, and the least effective osmotic stress adjustment compared to tetraploid and triploid plants. However, grafted diploid and triploid plants showed effective mitigation of drought-induced damage, with higher relative water content and improved soil water retention. Grafted plants also improved the photosystem response to drought stress through elevated photosynthetic potential, closed stomatal aperture, and faster recovery of chlorophyll biosynthesis in the leaves. Additionally, grafted plants altered osmotic protective compound levels, including starch, soluble sugar, and proline content, thereby enhancing drought resistance. Absolute quantification PCR indicated that the expression levels of proline synthesis-related genes in grafted plants were not influenced after drought stress, whereas they were significantly increased in self-rooted plants. Consequently, our findings support that self-rooted triploid and tetraploid mulberries exhibited superior drought resistance compared to diploid plants. Moreover, grafting onto seedling rootstocks enhanced tolerance against drought stress in diploid and triploid mulberry, but not in tetraploid. Our study provides valuable insights for a comprehensive analysis of physiological effects in response to drought stress between stem-roots and seedling rootstocks.

Laser etching of on-chip ultra-high stability flexible micro MnO2//Zn batteries

Micro zinc batteries have great potential in fields such as smart clothing, wearable devices, and implantable medical devices, due to their high-energy density and biocompatibility, etc. However, the side reactions in Zn anode have limited their lifespan. Here we design a high stable fork-finger-shaped electrode using laser etching to obtain MnO2//Zn flexible miniature zinc ion batteries. And then, a carbon slurry is introduced to inhibit hydrogen evolution to suppress the detachment of the zinc anode. Compared with Au/PET interface, the PET/C interface had lower water retention and higher hydrogen evolution production barrier based on first-principles calculation. The interdigital electrode based on PET/C/Au had good stability. The micro MnO2–Zn flexible battery showed high specific capacity of 0.091 mAh/cm2 at 0.1 mA. After 5000 cycles at 0.5 mA, the capacity retention rate reached 83.6%. This study of interdigital electrode by laser etching brings an inspired universal pathway to fabricate a reversible Zn anode for micro-zinc storage systems.

Influence of Date Palm-Based Biochar and Compost on Water Retention Properties of Soils with Different Sand Contents

Generally, soils of arid and semi-arid regions have low water retention properties due to high sand and low organic carbon contents. This study aimed at quantifying the effect of date palm-based organic amendments (OAs) on the water retention properties of two soils (sandy loam and silty loam), as well as the influence of sand supplementation (0.5–2 mm) on the magnitude of the effect of OAs. Different grain size distributions were obtained by adding sand to natural soils. For this purpose, sand was added to the two soils (1/3 and 2/3) and different soil-OA combinations were tested at a dose of 3% by mass: compost alone, biochar alone and a mixture of biochar and compost (50:50 in mass), in addition to unamended control soils. Soil water contents were measured at nine matric potentials ranging from the saturation to the permanent wilting point. Biochar was more efficient than compost at improving soil water retention. The effect of organic amendments on water retention increased with sand content. In most cases, soil water content values were significantly higher for biochar-amended soils than for unamended or compost-amended soils. The weakness of the effect of compost addition (if alone) was probably due to its properties and notably its high mineral content and electrical conductivity. Soil sand supplementation led to higher differences between the OA-amended soils and unamended soils. Changes in available water capacity reached +26% and +80% in a sandy loamy soil enriched with 2/3 sand and amended with compost and with biochar, respectively, compared to the unamended soil. These results show that sand content (and more generally, soil texture) influences the effect of OA application. Thus, the application of biochar from date palm residues in soil seems to be an effective solution to improve the water retention properties of coarse textured soils and contribute to optimizing the use of water resources in irrigated areas.

A new kinematic wave model that describes lateral subsurface flow and percolation in hillslopes

Kinematic wave (KW) models are commonly used for flood forecasting in large river basins, but have limitations in their ability to simulate percolation effects. Here, we suggest an extended KW model wherein the vertical pressure head is under non-hydrostatic conditions. The proposed model uses the Brooks Corey and Mualem models to estimate the water retention curve and unsaturated hydraulic conductivity and adopts the pressure head gradient as a new variable to calculate runoff based on changing water content distributions over time due to percolation. The increase in the pressure head gradient with rainfall infiltration is determined from the relationship between water storage and pressure head distribution, while the decrease in pressure head gradient due to percolation is modeled as exponential decay with time. A comparison of the proposed KW model and a numerical solution of the Richards equation shows that the proposed KW model can reproduce the storage effect caused by percolation, delaying runoff and reducing peak discharge. The agreement between the proposed KW model and the Richards equation is high for soils with high water retention. Conversely, the agreement becomes lower for soil with low water retention or deep soil layer thickness, where the complexity of water content distribution requires further refinement. The proposed model can easily be incorporated into distributed models while low computational cost with keeping the important percolation effects.

A Numerical Simulation of Moisture Reduction in Fine Soil Subgrade with Wicking Geotextiles.

A new wicking geotextile is proposed to control the water content of fine-grained soil subgrade. By comparing the spatial distribution of volumetric water content and matric suction before and after the installation of the wicking geotextile, the effectiveness of the geotextile in controlling the subgrade humidity is evaluated. Firstly, the hydraulic parameters of the wicking geotextile are obtained through laboratory tests using a pressure plate apparatus. Then, a numerical model for water flow in the subgrade is established using COMSOL to obtain the spatial distribution characteristics of humidity in the subgrade under different groundwater levels (2~8 m). The results show the wicking geotextile exhibits strong hydrophilicity, low water retention, and high horizontal permeability. Compared to the subgrade without geotextile, the water content of the soil above the geotextile decreases significantly by 7.6~9.6% at groundwater levels of 4~8m, while the saturation decreases by 18.3~23.0%, and the matric suction increases by 2~2.3 times. The wicking fabric functions as an effective drainage material to serve as a capillary barrier in the cross-plane direction and an effective drainage tunnel to transport water in the in-plane direction. The dynamic resilient modulus of the subgrade increases by 23.2~43.6%. The wicking geotextile effectively absorbs and drains weakly bound water in unsaturated soil due to the matric suction difference and its horizontal drainage capacity to improve the bearing capacity of the subgrade. It suggests that using wicking geotextile for drainage and reinforcement in fine-grained soil subgrades with groundwater levels ranging from 4 to 8 m is beneficial.