Soil Mixing Research Articles

Efficiency Evaluation of Deep Soil Mixing Method in Stiff Clayey Soils: A Comprehensive Field Study

Efficiency Evaluation of Deep Soil Mixing Method in Stiff Clayey Soils: A Comprehensive Field Study

Microbial depolymerization of Kraft lignin for production of Vanillic acid by indigenous ligninolytic strains

Lignin is a potential renewable source for the production of many value-added bio-products through bacterial depolymerization. In this study, Kraft lignin (KL) was depolymerized by indigenous potential ligninolytic strains to obtain the optimum amount of Vanillic acid. Initially, fifteen bacterial strains were isolated from decaying wood mixed soil to assess their lignin degradation efficiency. Five potential lignin-degrading microbes (RW-B2, RW-B4, RW-B9, RW-B11 and RW-B15) were identified by nutrient enrichment technique. RW-B15 was observed as a dominant strain sharing a 99 % resemblance to Bacillus megaterium sp. Optimum temperature and bacterial inoculum concentration were noted as 35 °C and 1 %, respectively. Mixed microbial culture of five potential ligninolytic strains showed better KL degradation than pure culture due to different metabolic capacities, enzymatic mechanisms and synergetic impact among the association members. The KL degradation study was conducted with different KL concentrations (500–2000 mg/l) at optimum temperature using 1 % inoculums. The production of Vanillic acid increased from 60.1 to 199.9 mg/l with increasing concentration of KL from 500 to 2000 mg/l. The maximum production of Vanillic acid was obtained on 3rd day of degradation and it decreased thereafter which is probably due to an increase in microbial toxicity and enzymatic activity. However, the COD level continuously decreased for all KL concentrations with degradation time till the last day. The pH of the KL solution slightly decreased on 3rd day due to the acidic nature of Vanillic acid. GC-MS analysis confirmed the presence of Vanillic acid and showed the presence of other monomeric compounds formed after KL degradation.

Biochar and Deactivated Yeast as Seed Coatings for Restoration: Performance on Alternative Substrates

Seedling establishment is often a critical bottleneck in the revegetation of mine tailings and similar substrates. Biochar and deactivated yeast are potential sustainable materials that could be used in this context as seed coatings to aid in seedling establishment. We conducted a greenhouse study on biochar and deactivated yeast use as seed coatings, assessing germination, establishment, and early growth of white clover (Trifolium repens) and purple prairie clover (Dalea purpurea). Coated seeds were applied to a mine tailing, a coarse granitic sand, and potting soil mix substrates; seedling establishment and growth were monitored over 75 days. Biochar coatings enhanced the seedling establishment of Trifolium, with biochar and biochar plus yeast coatings giving the best results. In some cases, these effects persisted throughout the experiment: biochar coatings resulted in a ~fivefold increase in Trifolium biomass at harvest for plants in the potting soil mix but had neutral effects on sand or tailings. Biochar seed coatings also enhanced Dalea germination in some cases, but the benefits did not persist. Our results indicate that biochar-based seed coatings can have lasting effects on plant growth well beyond germination but also emphasize highly species-specific responses that highlight the need for further study.

Impact of aeroponic cultivation and plant growth regulators on the biochemical composition of grapevine leaves

Background: Grapevine (Vitis vinifera L.) is a globally important perennial fruit crop, renowned for its economic value and cultural significance. Grape leaves, while often underappreciated, play a vital role in culinary traditions and are valued for their cultural, nutritional, and health benefits. However, the availability of grape leaves is constrained by viticulture practices and chemical treatments that prioritize fruit production over leaf harvesting. This study seeks to compare the biochemical characteristics of grapevine leaves from the cultivar 'Deghin Yerevani' grown from virus-free, tissue-cultured plants under aeroponic and soil conditions within a greenhouse. Objective: To evaluate the impact of aeroponic versus soil-based cultivation and the application of specific growth regulators on the biochemical composition and nutrient content of 'Deghin Yerevani' grapevine leaves, with the goal of optimizing conditions for high-quality leaf production. Materials and Methods: This study, conducted from 2021 to 2023 at the Scientific Center of Agrobiotechnology, ANAU, utilized virus-free in vitro plants of Vitis vinifera L. cv. 'Deghin Yerevani', sourced from the National Grape Field Collection. Plants were cultured in four treatment groups with varying growth media compositions: PGR-free, with Indole-3-acetic acid (IAA), with IAA and Gibberellic acid (GA₃), and with IAA, GA₃, and 6-Benzylaminopurine (BAP). Post-culturing, plants were transferred to either an aeroponic system, which used a misting cycle and maintained controlled environmental conditions, or to a greenhouse with a defined soil mix and monitored moisture levels. Both systems operated for 8 weeks, with each treatment replicated three times. Chlorophylls a and b, ascorbic acid, sugars, and macro- and micronutrient contents were analyzed, and statistical significance was determined using standard error and Student’s t-test (p < 0.05). Results: Grapevine leaves from 'Deghin Yerevani' plants grown in aeroponic systems exhibited significantly higher chlorophyll a, chlorophyll b, and total chlorophyll compared to those grown in soil. Growth regulators, particularly IAA, GA3, and BAP, enhanced chlorophyll content, sugar levels, and Vitamin C across both cultivation methods. Aeroponic systems showed superior results with increased sugar content (5.7 g/100g) and Vitamin C (20.4 mg/100g) compared to soil-based cultivation. Nutrient analysis revealed higher levels of nitrogen, phosphorus, potassium, calcium, and magnesium in aeroponics. Overall, growth regulators and aeroponic cultivation improved the biochemical and nutrient profiles of grapevine leaves. Conclusion: The study demonstrated that aeroponic cultivation and the application of growth regulators significantly enhanced the biochemical composition of grapevine leaves. Higher levels of chlorophyll, sugar, and Vitamin C, along with improved nutrient content, were observed in aeroponic systems compared to soil-based cultivation. These findings underscore the benefits of aeroponics and growth regulators in optimizing grapevine leaf quality, suggesting potential for improved yield and nutritional value in grapevine production. Keywords: 'Deghin Yerevani', grapevine, in vitro propagation, functional foods, Aeroponic Cultivation, Plant Growth Regulators

Detecting soil mixing, grain size distribution, and clogging potential of tunnel excavation face by classification-regression algorithms using EPBM operational data

Earth pressure balance machine (EPBM) operation is sensitive to the properties of the excavated soil due to the requirements of proper soil conditioning and maintenance of necessary chamber pressure. However, soil properties are invariably only available at a limited number of borehole explorations and soil samplings conducted during the subsoil investigation. Thus, it is crucial to identify properties of the tunnel excavation face, such as clay-sand mixed conditions, grain size distributions, and clogging potential along the whole alignment beside the few borehole locations to attain optimally efficient EPBM operation. Therefore, this paper presents the development of machine learning prediction models (i.e., classifiers and regressors) to estimate the properties of the tunnel excavation face using EPBM operational data collected during the tunneling operation as input features. Geotechnical data collected from boreholes and soil samples can be used to validate prediction models and calibrate them. To develop such models, the Northgate Link Extension (N125) tunneling project, constructed in Seattle, Washington, the USA, is used to capture and identify the true ground conditions. The results indicate successful prediction performances by the models, providing indication that EPBM parameters are crucial pointers of the tunnel excavation face properties to help attain optimally efficient EPBM operation.

In situ treatment of contaminated soil using persulfate activated by sulfidated zero-valent iron

Soil contamination with hazardous substances like phenol poses significant environmental and health risks. In situ soil mixing can be a promising technological solution to this challenge. A persulfate and sulfidated zero-valent iron (S-ZVIbm) system for remediating contaminated soil was developed and tested to be suited to in situ soil mixing. S-ZVIbm was synthesized using a ball mill process, and the optimal sulfur to iron molar ratio for effectively removing phenol from soil removal without pyrophoric risks was 0.12. Soil slurry experiments were performed, and the best phenol oxidation results (high stoichiometric efficiency and sustained oxidation after mixing) were achieved at a persulfate to S-ZVIbm molar ratio of 2:1 and a persulfate to phenol molar ratio of 8:1. A high organic matter content of the silty clay fraction of the soil strongly suppressed persulfate activation, so suppressed phenol removal and increased persulfate consumption. Electron spin resonance and radical scavenging tests confirmed that hydroxyl and sulfate radicals were present during the degradation of phenol. While sulfate radicals predominantly facilitated degradation in the soil, both sulfate and hydroxyl radicals were crucial in the aqueous phase in the absence of soil organic matter. In situ soil mixing simulation tests indicated that the persulfate and S-ZVIbm doses and the mixing rate and duration strongly affected the efficacy of the system, and the optimal conditions for phenol removal were determined. The results indicated that the persulfate/S-ZVIbm system could be tuned to achieve sustained persulfate activation and to remediate contaminated soil employing in situ soil mixing technique.

Effect of Pre-Harvest Intermittent UV-B Exposure on Growth and Secondary Metabolites in Achyranthes japonica Nakai Microgreens in a Vertical Farm

Achyranthes japonica Nakai (AJN) is a medicinal plant known to be beneficial for the joints. Since it takes at least two years from sowing to harvesting in an open field, new AJN cultivation strategies are needed to shorten the production period and improve quality. In this study, high-quality AJN is produced as microgreens in a vertical farm using a commercial ginseng soil mix (Myeongpum-Insamsangto, Shinsung Mineral Co., Ltd., Goesan, Republic of Korea) and controlled environmental conditions. The cultivation conditions included a temperature of 23 ± 2 °C, relative humidity of 50 ± 10%, and a photosynthetic photon flux density of 170 ± 15 µmol·m−2·s−1. Pre-harvest intermittent UV-B exposure, with an intensity of 1.0 ± 0.3 W/m−2, was applied for one day before harvest to evaluate its effects, using controlled environmental conditions in the vertical farm. Ultraviolet-B (UV-B) irradiation increases secondary metabolite levels in plants; however, the effect of UV-B on 20-hydroxyecdysone (20E), an indicator of AJN, is unclear. Therefore, we aimed to investigate whether UV-B treatment of AJN microgreens affected growth and secondary metabolites. The treatment group was set to 12 h of continuous UV-B treatment during the day, two 6 h UV-B treatments, and four 3 h UV-B treatments to confirm the effectiveness of regular and intermittent treatment and recovery. Short-term UV-B treatment before harvesting increased phenols, flavonoids, antioxidant capacity, and 20E levels without affecting AJN biomass. The intermittent 6 h UV-B irradiation with a 6 h recovery time stimulated 20E content by approximately 1.4 times compared to the control. These study findings indicate that short-term UV-B treatment before harvesting, an appropriate recovery time, and intermittent UV-B exposure are more effective at increasing 20E content than continuous treatment. This approach provides a promising strategy for improving the nutritional and health benefits of AJN microgreens in vertical farming systems.

Brownfield Topsoil Vertical Heterogeneity: Implications for Germination and Soil Microbial Functioning.

Soil vertical heterogeneity refers to the variation in soil properties and composition with depth. In uncontaminated soils, properties including the organic matter content and nutrient concentrations typically change gradually with depth due to natural processes such as weathering, leaching, and organic matter decomposition. In contaminated soils, heavy metals and organic contaminants can migrate vertically through leaching or root uptake and translocation by plants and macrobiota, if present, leading to vertical heterogeneity in contaminant concentrations at different depths. Contaminants can alter soil properties, and we investigated the implications of soil vertical heterogeneity for germination and microbial functioning. We collected soil from an urban brownfield and created two conditions: structured soil samples collected with the soil core intact and mixed (unstructured) samples. When planted, the germination rate was significantly lower in the structured conditions (3.1 ± 1.7%) compared to mixed soils (17 ± 4.6%), suggesting that the vertical heterogeneity of contaminated soil influenced plant germination. To map the vertical distribution of contaminants and nutrient cycling rates in the structured soil samples, we collected 10 cm-deep soil cores from the barren site and a neighboring vegetated reference site and measured heavy metal concentrations, soil enzyme activities, and organic matter content in five 2 cm vertical layers. In the barren soil cores, metals were found concentrated in the top 2 cm layer, while in the vegetated soil cores, metals were uniformly distributed. No significant differences were observed for the organic matter content or moisture along depth. Published studies on vertical distribution of enzyme activities and metal concentrations have treated the top 10-20 cm as a single layer and thus would have not revealed the thin (<2 cm thick) metal cap on the surface of the barren soil core. Despite the metal cap, enzyme activities in the top layer were similar to those in the lower layers of the barren soil core, suggesting that high metal concentrations do not limit soil enzyme activity under all circumstances. Investigating vertical heterogeneity in postindustrial soils can inform efforts to convert industrial barrens to vegetated environments.

Laboratory Investigation of Deep Soil Mixing for the Improvement of Salt-Cemented Soils

Laboratory Investigation of Deep Soil Mixing for the Improvement of Salt-Cemented Soils

First Report of Fusarium avenaceum Causing Root Rot of Raspberry (Rubus corchorifolius) in China.

Raspberry (Rubus corchorifolius) plants hold historical, economic, and medicinal importance in China (Yang et al. 2022). Raspberries are cultivated to generate income for local farmers in Lintao County, Dingxi City, Gansu Province. However, farmers encountered challenges due to raspberry plants exhibiting root rot disease, resulting in plant death. During a thorough field survey conducted in June 2022, symptoms ranging from leaf yellowing and wilting to necrotic lesions and root rots were observed, where approximately 30% of raspberry plants were affected. Five diseased and healthy plants were collected from the farmers' fields in Lintao (35.53oN, 103.84oE) for pathogen identification. Symptomatic and asymptomatic root tissues were surface sterilized with 75% ethanol for 30 s and 3% NaOCl for 5 min, followed by three rinses in sterile water. Small pieces (0.5 × 0.5 cm) were cut and incubated on potato dextrose agar (PDA) plates at 25°C for 7-10 days. Twenty-two pure Fusarium isolates, which displayed four distinct colony groups morphologically, were obtained. Pathogenicity tests on isolates RB10, RB1, RB30, and RB23, representing each colony group, revealed that RB10 exhibited symptoms similar to those observed in the field. The RB10 strain produced yellowish-white to greyish-white colonies on PDA and was then cultured in a carboxymethylcellulose (CMC) broth for enhanced conidia production (Zhang et al. 2020). Macroconidia were sickle-shaped or slightly curved, with three to five septa (19.2 to 38.5 x 3.1 to 5.8 µm, n =40). Microconidia were oval to ellipsoidal, non-septate or featuring 1 to 2 septa (4.8 to 10.5 x 2.1 to 5.2 µm, n=20). These morphological features indicated the isolate was similar to Fusarium avenaceum (Leslie and Summerell, 2006). For further identification of the strains, genomic regions (ITS-rDNA, TEF-1α, and RPB2) were amplified and sequenced using specific primers ITS1/ITS4, EF-1/EF-2, and 5f2/7cr, respectively (O'Donnell et al. 2010; Uwaremwe et al. 2021; Zarrin et al. 2016). PCR BLASTn queries of NCBI GenBank revealed a 99.8% (522 bp), 99.4% (355 bp) and 99.6% (985 bp) homology with F. avenaceum (MZ724839.1, MN271631.1, and MK185026.1), respectively. Sequences were deposited in GenBank (ITS, OR735571; TEF-1α, PP216660; RPB2, PP857820). One-year-old raspberry seedlings were planted in pots with a sterile soil mix (2:2:1 v/v ratio of soil, peat, and vermiculite) under controlled greenhouse conditions (23-26°C, 16h light/8h dark). A month post-planting, taproots were wounded in six pots and inoculated with 20 ml of conidia suspension (106 conidia/ml), while the other six pots were maintained as controls. After 14 days, RB10-infected plants showed symptoms similar to field observations, while controls remained healthy. The experiment was conducted twice, and re-isolation confirmed both the pathogenicity and identity of the pathogen. In the concatenated phylogenetic tree of ITS, TEF-1α and RPB2, strain RB10 was clustered with the F. avenaceum representative strains KG502, KG431 and F094. Studies revealed F. avenaceum varied pathogenicity across plants (Bugingo, 2022; Moparthi et al. 2020& 2024; Yli-Mattila et al. 2018), and it has been reported to induce raspberry fruit rot (Wang et al. 2017). However, no previous reports linked this fungus to raspberry root rot. This report is crucial for understanding the impact of root rot disease on raspberry cultivation and developing effective management strategies.

Soil cross breeding: Mechanical strength analysis of intermixed soils used as unfired earth brick

Mechanical strength of brick is significantly influenced by soil properties, deeming some soils unusable. This paper investigates the effect of mixing soils from different sources, Hyogo (a chlorite soil) and Tokyo (an albite soil) from Japan, on the flexural and compressive strength of unfired earth brick. Before conducting strength tests on moulded bricks made from original soil mixes and intermixed soils, both soil samples were individually separated into two portions, sand and fines. To better understand the strength behaviour of the resulting brick specimen, the physical and chemical properties of used raw materials were characterised using various techniques including X-ray computed tomography (X-ray CT) X-ray diffraction (XRD), water and nitrogen sorption, X-ray fluorescence (XRF) and ionic conductivity. The results revealed that the replacement of the fines portions in unadulterated soil mixes induced an increase in flexural and compressive strength for brick specimen made with albite soil, while significant reduction in strength was recorded with brick specimen made with fines portion replaced in chlorite soil. Furthermore, the former intermixed soil exhibited higher strengths than specimen made from unadulterated soils. Chlorite clay minerals comprised of desired properties to enhance performance of albite soil sand particles in a brick composite. This justified the dependence of selected soil parameters that play critical roles in the performance behaviour of the produced bricks. The obtained findings could serve as guidelines to production and performance enhancement of unburnt brick by amalgamating various soils.

IMPACT OF DIFFERENT ZINC APPLICATION METHODS AND PHOSPHORUS DOSES ON GROWTH, YIELD AND GRAIN ZINC CONTENTS OF WHEAT

Wheat is a staple crop of around half of the world's population. About 30 percent of the world’s population is suffering from Zn deficiency. Zn deficiency problems can be encountered by agronomic and genetic biofortification. Phosphorus (P) is an important plant macronutrient and has an antagonistic relationship with Zn. A field study was performed to evaluate the impact of different Zn application methods and P doses on growth, yield, and grain Zn contents of wheat at the Agronomic Research Farm, University of Agriculture Faisalabad, Pakistan, using a high accumulation wheat variety Zincol-2016. Three doses of P (100, 150, and 200% of recommended P) along with three Zn application methods (seed priming, soil mixing, and foliar application) were applied to wheat using randomized complete block design (RCBD) with three replicates under split-plot arrangement. All agronomic practices were kept normal and uniform for all treatments. Parameters including growth, yield, and Zn content in wheat grains were monitored using standard protocols. The results were evaluated using Fisher’s analysis of variance at a 5% probability level. A comparison of means of treatments was performed using the least significant difference (LSD) test. The highest value of SPAD reading (56.38) was noted in treatment where Zn was applied as priming and P was applied at 200%. Maximum crop growth rate (63.17) was observed in P3 where Zn was applied as mix in soil. Maximum spike length (14.25), spikelets per spike (17.67), and Zn concentration were observed in P3 as a result of foliar application of Zn. Highest grain weight per spike (1.89g), no. of tillers (691.01), grain yield (4.09 t ha-1), biological yield (11.01 t ha-1), harvest index (36.54%) and NDVI (0.42 were observed in P3 where Zn was applied as soil mix.

Experimental Study on Mechanical Properties of Recycled Aggregate Mixed Soil.

In the context of efforts aimed at reducing carbon emissions, the utilization of recycled aggregate soil mixes for soil stabilization has garnered considerable interest. This study examines the mechanical properties of mixed soil samples, varying by dosage of a soft soil curing agent C, recycled aggregate R content, and curing duration. Mechanical evaluations were conducted using unconfined compressive strength tests (UCS), field emission scanning electron microscopy (FESEM), and laser diffraction particle size meter tests (PSD). The results indicate that the strength of the mixed soil samples first increases and then decreases with higher dosages of recycled aggregate, reaching optimal strength at a 20% dosage. Similarly, an increase in curing agent dosage enhances the strength, peaking at 20%. The maximum strength of the mixed soils is achieved at 28 days under various proportions. The introduction of the curing agent leads to the formation of a flocculent structure, as observed in FESEM, which contributes to the enhanced strength of the soil mixes. Specimens prepared with a combination of 20% R and 20% C, maintained at a constant moisture content of 20%, and cured for 28 days exhibit a balance between economic, environmental, and engineering performance.

Experimental Study on Static and Dynamic Characteristics of Sand–Clay Mixtures with Different Mass Ratios

The alteration of soil static and dynamic characteristics induced by clay content constitutes a crucial issue in the realm of disaster prevention and mitigation within geotechnical engineering. The static and dynamic characteristics of mixed soils with varying sand–clay contents were investigated through the design and implementation of static and dynamic triaxial tests. The relationship between clay content and soil resistance to liquefaction was investigated, with an analysis of the influence of clay content on soil strength and static liquefaction performance. Furthermore, the study examined the soil’s resistance to liquefaction under dynamic constitutive and cyclic loading conditions for soils with varying clay content. Results indicate that stress–strain curves for samples with varying clay content exhibit a consistent trend, with the lowest tangent modulus and peak strength observed in samples containing 30% clay. Increasing clay content diminishes soil’s resistance to liquefaction under static loading conditions. Higher confining pressures correspond to larger tangent moduli and peak deviating stresses in triaxial shear tests. Dynamic shear modulus decreases as clay content increases, whereas damping ratio decreases accordingly. Soil gradation significantly affects liquefaction-induced deformation, with the sample containing 30% clay experiencing the fastest increase in pore water pressure during testing failure, accompanied by fewer cyclic loading cycles until failure occurs. Improving soil gradation and adjusting the sand–clay ratio are beneficial for enhancing both soil strength and its resistance to liquefaction.

A Ground-Penetrating Radar-Based Study of the Structure and Moisture Content of Complex Reconfigured Soils

To increase the detection accuracy of soil structure and moisture content in reconstituted soils under complex conditions, this study utilizes a 400 MHz ground-penetrating radar (GPR) to examine a study area consisting of loess, sandy loam, red clay, and mixed soil. The research involves analyzing the single-channel waveforms and two-dimensional images of GPR, preprocessing the data, obtaining envelope information via amplitude envelope detection, and performing a Hilbert transformation. This study employs a least squares fitting approach to the instantaneous phase envelope to ascertain the thickness of various soil layers. By utilizing the average envelope amplitude (AEA) method, a correlation between the radar’s early signal amplitude envelope and the soil’s shallow dielectric constant is established to invert the moisture content of the soil. The analysis integrates soil structure and moisture distribution data to investigate soil structure characteristics and moisture content performance under diverse soil properties and depths. The findings indicate that the envelope detection method effectively identifies stratification boundaries across different soil types; the AEA method is particularly efficacious in inverting the moisture content of reconstituted soils up to 3 m deep, with an average relative error ranging from 2.81% to 7.41%. Notably, moisture content variations in stratified reconstituted soils are more pronounced than those in mixed soil areas, displaying a marked stepwise increase with depth. The moisture content trends in the vertical direction of the same soil profile are generally consistent. This research offers a novel approach to studying reconstituted soils under complex conditions, confirming the viability of the envelope detection and AEA methods for intricate soil investigations and broadening the application spectrum of GPR in soil studies.

Role of ectomycorrhizal colonization in enhancement of nutrients for survival of plants collected from mountainous cold stress areas

BackgroundEctomycorrhizal (ECM and ECM-like) structures associated with plant root systems are a challenge for scientists. The dispersion pattern of roots within the soil profile and the nutritional conditions are both favourable factors to motivate the plants to make ECM associations.ResultsThis study discusses the colonization of mycorrhizal associations in Kobresia and Polygonum species including Polygonum viviparum, Kobresia filicina, K. myosuroides, Alnus nitida, Betula pendula, Pinus sylvestris, and Trifolium repens grown naturally in cold stressed soils of Gilgit-Baltistan (high-altitude alpine Deosai plains), Hazara, Swat, Dir, and Bajaur. Sieved soil batches were exposed to +5 °C (control), -10, -20, -30, -40, -50, -125 °C for 5 h, and selected plants were sown to these soils for 10 weeks under favourable conditions for ECM colonization. Ectomycorrhizal associations were examined in the above mentioned plants. Some ECM fungi have dark mycelia that look like the mantle and Hartig net. Examples of these are Kobresia filicina, K. myosuroides, and Polygonum viviparum. Findings of this study revealed that K. myosuroides excelled in ECM root tip length, dry mass, and NH4 concentration at -125 °C. Contrarily, A. nitida demonstrated the lower values, indicated its minimum tolerance. Notably, T. repens boasted the highest nitrogen concentration (18.7 ± 1.31 mg/g), while P. sylvestris led in phosphorus (3.2 ± 0.22 mg/g). The B. pendula showed the highest potassium concentration (9.4 ± 0.66 mg/g), emphasising species-specific nutrient uptake capabilities in extreme cold conditions. The PCA analysis revealed that the parameters, e.g., NH4 in soil mix (NH4), NO3 in soil mix (NO3), phosphorus in soil in species of Polygonum viviparum, Kobresia filicina, K. myosuroides, Alnus nitida, Betula pendula, Pinus sylvestris, and Trifolium repens are most accurately represented in cases of + 5 °C, -10 °C, and -20 °C temperatures. On the other hand, the parameters for ECM root tips (ECM) and Dry Mass (DM) are best described in -40 °C, -50 °C, and − 125 °C temperatures. All parameters have a strong influence on the variability of the system indicated the efficiency of ECM. The heatmap supported the nutrients positively correlated with ECM colonization with the host plants.ConclusionAt lower temperatures, hyphae and spores in roots were reduced, while soluble phosphorus concentrations of leaves were increased in cold stress soils. Maximum foliar nutrient concentrations were found in K. myosuroides at the lowest temperature treatments due to efficient functioning and colonization of ECM.

Effect of Guar Gum Content on the Mechanical Properties of Laterite Soil for Subgrade Soil Application.

Using biopolymers for soil stabilization is favorable compared to more conventional methods because they are more environmentally friendly, cost-effective, and long-lasting. This study analyzes the physical properties of guar gum and laterite soil mixes. A comprehensive engineering study of guar gum-treated soil was conducted with the help of a brief experimental program. This study examined the effects of soil-guar gum interactions on the strengthening behavior of guar gum-treated soil mixtures using a series of laboratory tests. The treated laterite soil's dry density increased marginally, while its optimum moisture content decreased as the guar gum increased. Treatment with guar gum significantly enhanced the strength of laterite soil mixtures. For laterite soil with 2% guar gum, the unsoaked CBR increased by 148% and the soaked CBR increased by 192.36%. The cohesiveness and internal friction angle increased by 93.33% and 31.52%, respectively. These results show that using guar gum dramatically improves the strength of laterite soil, offering a more environmentally friendly and sustainable alternative to traditional soil additives. Using guar gum in T8 subgrade soil requires a 1395 mm pavement depth and costs INR 3.83 crores, 1.52 times more than laterite soil. For T9 subgrade soil, the depth was 1495 mm, costing INR 4.42 crores, 1.72 times more than laterite soil. This study introduces a novel approach to soil stabilization by employing guar gum, a biopolymer, to enhance the physical and mechanical properties of laterite soil. Furthermore, this study provides a detailed cost-benefit analysis for pavement applications, revealing the financial feasibility of using guar gum despite it requiring a marginally higher initial investment.

Revisiting mixing uniformity effect on strength of cement-based stabilized soft clay

Despite the fact that mixing uniformity (i.e. the consistency of binder distribution) significantly influence the quality of ground improvement during in situ soil mixing projects, its quantitative evaluation was rarely concerned due to the difficulty of measurement from an engineering perspective. A methodology was proposed to quantitatively evaluate the mixing uniformity of stabilized soil using handheld X-fluorescence spectrometry (XRF), which is helpful to elucidate the significance of mixing uniformity on strength. In other words, the calcium content was monitored to ascertain the distribution of cement within the matrix, and a quantitative index was subsequently established. It was observed that an increase in mixing uniformity resulted in a transition in the behavior of the stabilized clay from a plastic to a brittle failure mode, and from a localized failure to a global shear failure under unconfined compression. Subsequent observation of the destruction process revealed that cracks were more readily formed in the low cement zones and then bypass the high cement zones. Furthermore, the effect of mixing uniformity on strength is likely to be amplified with prolonged curing periods. The enhancement of uniformity would increase the volume of the high binder zones, thereby enhancing the overall high-strength performance. The proposed methodology is capable of characterizing the discreteness between the tracked element's measured and theoretical contents, thusing avoiding the uncertainty associated with other indirect indicators. The convenience of the portable handheld XRF apparatus was confirmed, as it can be readily deployed in situ or ex situ to track calcium content within the stabilized mass after borehole sampling.

Arbuscular mycorrhizal fungi increased biomass, nutritional value, and cochineal resistance of Opuntia ficus-indica plants

BackgroundOpuntia ficus-indica (L.) Miller is dominantly growing on degraded soils in arid and semi-arid areas. The plants might establish a strong association with arbuscular mycorrhizal fungi (AMF) to adapt to nutrient, drought, and herbivore insect stress. The objective of this study was to investigate the effects of AMF inoculations and variable soil water levels (SWA) on the biomass, nutrient concentration, nutritional composition, and nutrient digestibility of the spiny and spineless O. ficus-indica by inducing resistance to cochineal stress. One mother Opuntia ficus-indica cladode was planted in a single pot in each field with 24 kg mixed soil. AMF inoculums were cultured in sorghum plants in a greenhouse and were inoculated in the planted cladodes. The planted cladodes were arranged using a completely randomized design (CRD) with three factors: AMF (present and absent); O. ficus-indica type (spiny and spineless) and four water treatments with 0–25% of plant available soil water (SWA), 25–50% of SWA, 50–75% of SWA, and 75–100% of SWA.ResultsDrought stress reduced the below and above-ground biomass, cladode nutrient content, nutritional composition, and in vitro dry matter digestibility (IVDMD) and in vitro organic matter digestibility (IVOMD). AMF colonization significantly increased biomass production with significant changes in the macro and micro-nutrient concentrations of O. ficus-indica. AMF inoculation significantly increased the IVDMD and IVOMD of both O. ficus-indica types by improving the biomass, organic matter (OM), crude protein (CP), and reduced fiber and ash contents. AMF-inoculated cladodes improved the nutrient concentrations of the cladodes. AMF caused an increase in biomass production, increased tolerance to cochineal stress, and improved nutrient concentration, nutritional composition, and nutrient digestibility performance of O. ficus-indica plants.ConclusionsAMF improved the performance of the O. ficus-indica plant to resist drought and cochineal stress and increased the biomass, nutrient concentration, nutritional composition, and nutrient digestibility. The potential of O. ficus-indica to adapt to cochineal stress is controlled by the macro and micro-nutrient concentration brought by the AMF association.

Temporal effect and evolution mechanism of sand-bentonite mixture liner swelling under the influence of sand and diesel

To elucidate the time-dependent swelling behavior of landfill sand-bentonite mixture liners under the effect of organic pollutants, an no loading swelling ratio test was conducted on mixtures with varying sand and diesel content. The evolution characteristics of the swelling time curve morphology were investigated. The micro-mechanisms underlying the swelling time effect evolution were explored. The results indicated that the sand-diesel interaction significantly altered the swelling time curve morphological characteristics of the mixture. As the sand content increased, the swelling coefficient at the stable state decreased. However, during the rapid swell phase, diesel-contaminated mixed soil does not exhibit the increase-then-decrease pattern in swell coefficient seen in unpolluted mixed soil. The duration of both the slow swelling phase and the time to reach a stable state were longer. Mechanistic analysis revealed that cation exchange capacity is insufficient to effectively analyze the evolution characteristics of the swelling time curve. Instead, the initial swelling potential of bentonite is the true indicator of the mixture’s swelling properties. The particle size distribution influences the changes in the swelling coefficient during the rapid swelling phase, but diesel alters the particle size distribution, mitigating its impact. The oil sealing effect within intra-aggregate and inter-aggregate pores not only weakened the swelling characteristics of the mixture at all stages but also increased the permeability resistance, thereby reducing the duration of the rapid swelling phase and extending the slow swelling and stable swelling phases.