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Eight-year-old Loblolly pine (Pinus taeda) plots located in South Carolina were evaluated using high resolution aircraft multispectral scanner data to determine if biomass could be accurately measured. Sixteen pine plots located on both sandy and clay soils were treated with 0, 180, or 360 kg. (approximately 0, 400, or 800 lb.) of nitrogen per plot. Indices of biomass from remote sensing data were significantly correlated with in situ biomass measurements made in each plot. A ratio of infrared (9 - 1.1 μm) and red ( 65-70 μm) channels yielded the best correlation. The indices were not sensitive to differences in soil type (sandy or clay). [ABSTRACT FROM AUTHOR]

• There was no great variation in wavelength sizes between sandy and clayey soil. • For the frequency of 45 kHz, specimens of at least 200 mm are required. • Between 5 and 7 waves are required to have flat waves. • The smallest discontinuity detected by the ultrasound was between 8 and 19 mm. Considering this parameter, the minimum length of a soil test specimen to be compacted, to enable its characterization, was determined using ultrasonic testing. The experimental stage involved the production of specimens in different lengths for two types of soils (clayey and sandy) and three compaction energies (normal, intermediate, and modified). Ultrasound tests were performed after molding (0 days) and 28 days of compaction, using 45 kHz frequency longitudinal transducers and compression wave. The results indicated that the minimum length of the specimen should be 200 mm when the velocity stabilization occurred for the Clayey and Sandy soils. However, the factors considered (transducer frequency, compaction energy and apparent specific mass) may infer significant changes in wavelength. [ABSTRACT FROM AUTHOR]

The major objective of this study is to correlate rocking foundation performance parameters with their capacity parameters and earthquake demand parameters using results obtained from 142 centrifuge and shaking table experiments, which include a variety of soil conditions, foundation geometries, structural models, and types of ground motions. The analysis presented in this paper considers all experimental results together, collectively as big data, through nondimensional parameters to identify hidden relationships among different parameters in a capacity-demand-performance framework. Rocking system performance parameters such as seismic energy dissipation in soil, permanent settlement, peak and permanent rotation, tipping-over stability ratio, self-centering ratio, rocking moment capacity, and acceleration amplification ratio are correlated with rocking system capacity parameters such as critical contact area ratio, rocking coefficient, and slenderness ratio of rocking systems and the earthquake demand parameters such as Arias intensity and peak ground acceleration of earthquake. It is found that energy dissipation and settlement correlate reasonably well with rocking coefficient and Arias intensity of earthquake, while peak rotation and acceleration amplification ratio correlate reasonably well with slenderness ratio, rocking coefficient, and peak ground acceleration of earthquake. Rocking foundations in clayey soils show superior performance in terms of seismic energy dissipation and permanent settlement compared to those in sandy soils, especially for relatively small to medium intensity shakings, and the ability of rocking foundations to de-amplify the earthquake motion increases as the magnitude of shaking increases. • The research presented in this paper analyzes the results obtained from 142 dynamic base shaking experiments on rocking foundations conducted in centrifuges and shake tables. • The analysis presented in this paper considers all experimental results together, collectively as big data, through nondimensional parameters to identify hidden relationships among rocking foundation parameters. • Rocking foundation performance parameters are correlated with rocking system capacity parameters and earthquake demand parameters using experimental results. [ABSTRACT FROM AUTHOR]

• Biochar aging increased microbial carbon use efficiency (CUE) due to increase in pH. • Biochar aging decreased soil microbial biomass turnover time (BTT). • CUE was soil specific with higher CUE in sandy-textured soil than clay rich soil. • BTT was longer in a clay rich soil than in a sandy soil. Biochar amendment causes immediate increases in soil organic carbon (SOC), but long-term effects are unclear. Biochar properties change with time (biochar aging) potentially affecting how efficiently SOC remains in soil after decomposition, indicated by microbial carbon use efficiency (CUE, the ratio of microbial growth over carbon uptake). Effects of fresh and aged biochar amendments on microbial CUE and biomass turnover time (BTT) were determined using the H 2 18O-DNA incorporation method. Biochar aging increased CUE (control vs. fresh vs. aged of 0.6 vs. 0.6 vs. 0.7) but decreased BTT (51 vs. 37 vs. 27 days) due to changes in soil pH. Moreover, a greater CUE but shorter BTT was found in the sandy-textured Tenosol compared to the clayey Dermosol, possibly due to protection by clay minerals. Biochar aging and associated increase in soil pH may promote soil biogenic carbon sequestration through increasing microbial CUE or decreasing BTT. [ABSTRACT FROM AUTHOR]

• Sandy soils reach moderate penetration resistance at field capacity. • In semi-arid climates and sandy soils, low penetration resistance occurs infrequently. • Penetration resistance in clay soils is below 10 MPa even during the dry season. • In seasonally dry climates, penetration resistance follows a beta distribution. • Wet season rainfall affects year-round penetration resistance distribution. In water-controlled environments, because rainfall is one of the primary hydroclimatic forcings, its variability can affect the dynamics of soil water content and other related processes such as soil penetration resistance (PR), plant growth, and food production. The objective of this study was to simulate the relative soil water content (s) and PR year-round considering semi-arid rainfall conditions for different soil classes. An experiment was conducted to obtain relative soil water content (s) and PR data in sandy soil and this information was combined with a data set of four soils from a similar experiment conducted on different soil texture classes. The relative soil water content and PR were simulated at a daily timescale using a stochastic soil water balance model for the five soils. The parameters of the PR - s model can be estimated from the soil texture and bulk density. Under rainfed conditions, there is a short window for tillage (plowing and cultivation) of sandy soils compared with clay soils. During the majority of a typical hydrological year, the PR reaches high values (greater than 5.0 MPa) imposing a moderate to high physical limitation for root growth in sandy soils. In the same soils, limiting PR is reached at s levels very close to the field capacity during the drying process. This indicates that an extra input of water through irrigation may be required during the establishment of crops with a well-developed root system in order to prevent impairments to root growth. The daily PR values modeled over the course of a hydrological year followed a beta distribution with shape parameters (α and β) which were strongly correlated with the frequency of rainfall events during the wet season (λ wet). The modeling framework presented here for simulating relative soil water content and soil penetration resistance can be applied to agricultural systems in order to prevent physical limitations on crop growth and to plan tillage management schedules. [ABSTRACT FROM AUTHOR]

The rate-dependent uniaxial compressive behavior of frozen clay soil is strongly affected by its minerals, void ratio, stress history, and pore fluid salinity. Previous studies show that an extremely low deformation rate applied on a clay soil tends to result in a lower bound compressive strength. However, the lower bound stress-strain behavior of frozen clay soil under the uniaxial compressive condition was not studied. A thorough understanding of the rate-dependent behavior of frozen clay and its relationship with temperature requires a large number of specimens with similar compositions and micro-structures. In this study, a series of laboratory tests were carried out on artificial frozen sandy clay soils to measure the rate-dependent uniaxial compressive behavior at temperatures ranging from −15 °C to 0 °C. We used two types of artificial frozen clay soils with pre-determined clay fraction, clay mineralogy, stress history, and moisture content. Our results conclude that a low temperature and a high deformation rate tend to generate brittle failure with post-peak softening behavior. A temperature close to the freezing temperature and a low deformation rate result in a diffuse failure associated with strain hardening. Temperature-dependent uniaxial compressive mechanical properties were measured and modeled using empirical relations, which are highly dependent on the applied deformation rate. A series of step-loaded relaxation tests were carried out on those artificial clay soils and creep parameters were estimated using relaxation test results and a power law creep model. A new approach of deriving the lower bound of stress-strain curve of frozen soil is proposed accordingly. The idea of determining the lower bound of stress-strain curve is based on the isotache concept, which was previously used in the soil consolidation theory. • Temperature-dependent uniaxial compressive and relaxation behaviors of artificial frozen sandy clay soils are measured. • Relations between creep parameters and temperatures of frozen clay soils are displayed. • A new approach of deriving the lower bound of stress strain curve of frozen soil is proposed. [ABSTRACT FROM AUTHOR]

New technologies have been developed to slow down the phosphorus release in the soil and prevent the loss to the environment by using layered double hydroxides (LDH). However, slow-releasing mechanisms in inorganic matrices are not often discussed in the literature, and post-release sorption-desorption processes have also not been taken into account. Thus, kinetic and sorption processes of P in soils were herein investigated employing a modified LDH. The modification was carried out by the reconstruction method in the P solution. The material (HTCP) was characterized by FT-IR and XRD. The release of P to the soil solution was slow. Around 11% of the P introduced in the LDH was released to the clayey soil solution, and 5.5% to the sandy soil solution over 45 days (1080 h). Kinetic models of first-order and second-order, Elovich, intraparticle diffusion, and power function were applied. The intraparticle diffusion model best described the P release in clayey soil, characterizing ion exchange, while the second-order model better adjusted the release in sandy soil. The dual-mode Langmuir-Freundlich model appropriately described the sorption of P in the soil samples, being the desorption almost null. Although some of the P was sorbed, the post-sorption pH remained in a viable range for making P available to the plants, revealing the benefits of using HTCP for slow-release fertilizers. Unlabelled Image • Mimicking soil solution for phosphorus release. • Rigorous statistic methods for interpretation of release results. • Kinetic models described in detail for support the release hypothesis. • Sorption-desorption studies of phosphorus after slow-release. • Availability of phosphorus species after slow-release. [ABSTRACT FROM AUTHOR]

The damping-off incidence caused by Pythium aphanidermatum in chilli was 20.0 and 58.0% post-emergence at 7 and 20 days after sowing, respectively in clay soil. Among 4 different soils, clay soil favoured the disease most and recorded the maximum fungal population of 12.46×103 cfu/g of soil at 20 days after sowing. The incidence of disease was comparatively low in sandy soil. [ABSTRACT FROM AUTHOR]

Management of the soil microbial community to increase crop productivity is one of the main challenges of modern agriculture, and bacterial inoculants can help to overcome this challenge. In this work, two plant growth-promoting (PGP) bacteria were evaluated under contrasting soil conditions, in order to test a rhizosphere ecology model. This model states that plants select for phosphate (P) solubilizers in poor nutrient soils and Indolic Compounds (ICs) producers in rich nutrient soils. Rice plants were single- or co-inoculated with strains of Burkholderia and Enterobacter genera in clayey and sandy soils. Diversity gradients were generated in each soil type using the dilution-to-extinction approach. Inoculant survival, colonization, and effect on plant biomass were evaluated, besides P solubilization and ICs production from both rhizospheric and endophytic bacterial communities. The PGP efficiency of the Burkholderia strain was highest in the sandy soil, which had the highest bacterial P solubilization potential, whereas the PGP efficiency of the Enterobacter strain was highest in the clayey soil, which had the highest bacterial ICs production potential. These behaviors occurred as hypothesized by the model, which can be useful for PGPB testing and bioprospection. We highlight a strong dependency of the Enterobacter strain on the diversity level as the most critical factor affecting PGP efficiency, possibly related to the increased influence of keystone taxa in lower diversity as indicated by network analysis. • Bacterial plant growth promotion effect was successfully predicted by functional traits. • Microbial inoculation efficiency was diversity-dependent, with greater effects in low diversity. • Microbial production of plant hormones was negatively correlated to nutrient solubilization. • Number of keystone taxa decreased with diversity, but their network influence increased. [ABSTRACT FROM AUTHOR]

Wireless Underground Sensor Networks (WUSNs), an important part of Internet of things (IoT), have many promising applications in various scenarios. Signal transmission in natural soil undergoes path loss due to absorption, radiation, reflection and scattering. The variability and dynamic of soil conditions and complexity of signal attenuation behavior make the accurate estimation of signal path loss challenging. Two existing propagation models for predicting path loss are reviewed and compared. Friis model does not consider the reflection loss and is only applicable in the far field region. The Fresnel model, only applicable in the near field region, has not considered the radiating loss and wavelength change loss. A new two stage model is proposed based on the field characteristics of antenna and considers four sources of path loss. The two stage model has a different coefficient m in the near field and far field regions. The far field distance of small size antenna is determined by three criteria: 2 D2/λ, 5 D, 1.6 λ in the proposed model. The proposed two stage model has a better agreement with the field experiment data compared to Friis and Fresnel models. The coefficient m is dependent on the soil types for the proposed model in near field region. It is observed from experiment data that the m value is in the range of 0~0.20 for sandy soils and 0.433~0.837 for clayey silt. [ABSTRACT FROM AUTHOR]

• The mechanism in the interaction of the low water clays and jet grout is a combination of erosion and cutting. • Clays at low water content interact with jet pressure similar to silt and sandy soil. • An equation was proposed to estimate the diameter of the soilcrete column in low water content clays. • Optimum injection pressure for single-fluid jet grouting in clayey soil at low water content is 45 MJ/m. One drawback to the application of jet grouting for soil improvement is quality control, especially the determination of the diameter and strength of the column, which depends on the technical specifications of the injection and soil type. It has been reported that the initial water content of the clay effects the erosion of cohesive particles. The compressive strength and diameter of a soilcrete column in clay/sand at different jet grouting specifications have been well documented. However, the effect of the initial water content of clay on the performance of the jet grouting method has not been reported. Researchers have not proposed technical specifications for single-fluid jet grouting in remoulded clay with a low water content. The present study carried out 10 full-scale tests to analyse the effect of single-jet grouting specifications on the diameter and uniaxial compressive strength of soil-cement columns in a reclaimed area with low water content clay. The clay-jet grout interaction was evaluated using a microstructural approach and revealed that there is insufficient cohesion between the particles of remoulded clay. The mechanisms of interaction between the particles and the jet grouting is a combination of erosion and penetration of the grout into the soil and into air-filled cracks. In this case, it caused the particles to behave in a manner that is similar to that of silt and sandy soil. The efficiency of jet grouting in this type of soil was better than in clayey soil with a high water content. Thus, the equation previously used to estimate the diameter of the column has been modified by increasing the reference diameter from 50 to 60 cm for clayey soil with a low water content. The results show that an increase in the time interval and decrease in lifting step reduced the number of clayey clods in the core and increased the strength of the soil-cement. The maximum strength and diameter were achieved at an energy of 25 MJ/m with an optimum injection pressure of 45 MPa for single-fluid. [ABSTRACT FROM AUTHOR]

• A two-year field experiment with rooting depth treatment was performed in clay and sandy soil. • Deep roots in maize contribute to increase N uptake and grain yield in sandy soil. • Increasing root length below 40 cm depth can reduce nitrate leaching in clay soil. Increasing rooting depth via subsoiling is suggested to increase nitrogen (N) uptake and reduce nitrate leaching in maize. In a two-year field experiment, this hypothesis was evaluated with two levels of N supply (120 and 240 kg N ha−1) in two soils with different leaching potential (infertile sandy soil and fertile clay soil). Maize rooting depth was limited to either the 0–20 cm (D20) or 20–40 cm (D40) soil layer using a nylon net (30 μm), or was not limited (control). There was no water stress during the growing seasons for both soils. Compared to the control, root length with the D20 and D40 treatments was longer in the 0–20 and 20–40 cm soil layers, respectively. However, total root length per plant differed less among the treatments. In clay soil, the D20 treatment did not affect N uptake, shoot biomass, or maize yield, but increased nitrate leaching. In sandy soil, the D20 treatment greatly reduced plant N accumulation, shoot biomass, and grain yield, while nitrate leaching was similar across the three treatments. It is concluded that deeper roots in maize contribute to increase N uptake and grain yield in sandy soil, but only help to reduce nitrate leaching in clay soil. [ABSTRACT FROM AUTHOR]

Statistical characterization of model uncertainty has been exclusively focused on reliability-based design of soil nail walls against ultimate limit states; little has been accomplished for predictions of horizontal and vertical displacements at the top of the wall for analysis of serviceability limit states. To fill the gap, this study first develops a database containing 461 measured wall horizontal and vertical displacements from 75 fully instrumented soil nail walls under working conditions reported in the literature. Then, the database is used to evaluate the accuracies of simplified wall displacement models currently adopted in four national soil nail wall design manuals. The results show that on average the current models tend to over-predict displacements for walls in sandy soils, but under-predict displacements for walls in clayey soils. Predictions using the current models are moderately to highly dispersive. Simple models are developed and calibrated for prediction of displacements based on the established database. Predictions using the developed models are demonstrated to be accurate on average and significantly less dispersive. In addition, a simple model for prediction of horizontal wall displacement along depth is developed and optimized. The present work is practically valuable for reliability-based design of soil nail walls against serviceability limit states. [ABSTRACT FROM AUTHOR]

Soils are among the most biodiverse and densely inhabited environments on our planet. However, there is little understanding of spatial distribution patterns of belowground biota, and this hampers progress in understanding species interactions in belowground communities. We investigated the spatial distribution of nematodes, which are highly abundant and diverse metazoans in most soil ecosystems. To gain insight into nematode patchiness, we mapped distribution patterns in twelve apparently homogeneous agricultural fields (100 m × 100 m each) with equal representation of three soil textures (marine clay, river clay and sandy soil). Quantitative PCRs were used to measure the abundances of 48 distinct nematode taxa in ≈1200 plots. Multivariate analysis showed that within this selection of sites, soil texture more strongly affected soil nematode communities than land management. Geostatistical analysis of nematode distributions revealed both taxon-specific and field-specific patchiness. The average geostatistical range (indicating patch diameter) of 48 nematode taxa in these fields was 36 m, and related to soil organic matter. Soil organic matter content affected the spatial variance (indicating within-field variation of densities) in a life-strategy dependent manner. The r-strategists (fast-growing bacterivores and fungivores) showed a positive correlation between organic matter content and spatial variance, whereas most K-strategists (slow-growing omnivores and carnivores) showed a negative correlation. Hence, the combination of two parameters, soil organic matter content and a general life-strategy characterisation, can be used to explain the spatial distribution of nematodes at field scale. • Nematode distribution maps show taxon- and field-specific levels of patchiness • Distributions of nematodes with similar food preferences show little or no overlap • Soil organic matter affects nematode patchiness in a life-strategy dependent manner • Stochasticity is a dominant driving factor for mesoscale distribution of nematodes • Distribution maps enable the design of soil sampling schemes with known accuracies [ABSTRACT FROM AUTHOR]

DNA-tagged particle tracers have been the subject of several researches as a new tracer for hydrological applications. This tracer potentially permits the production of a large number of identically transported but distinguishable tracers. Such technique facilitates multi-point and multi-time tracer experiments in a specific location without confounding the signal of the different tracers. All of those potential benefits of DNA-tagged particles can effectively improve our understanding on contamination flow origin and its pathways in the subsurface environment.In this study the effect of soil size on the transport of DNA-tagged silica particles is evaluated. We assumed that the presence of preferential flow pathways or dual porosity in a clayey soil can lead to negligible mass recovery rate of tracer in comparison to matrix flow in sandy soil. Thereto, a series of soil column laboratory tests under saturated conditions were conducted. The columns are custom-designed with a diameter of 25 cm and a height of 25 - 28 cm. The columns were in-situ excavated from a clayey Holocene soil from West of the Netherlands; and from a sandy Pleistocene soil from the East of the Netherlands. We not only determined mass recovery rates and advective-dispersive transport parameters of the colloidal DNA-tagged silica particle tracer, but also compared DNA tracer data with deuterium tracer data, applied to the same columns. Finally, we defined the role of preferential flow paths in the columns. [ABSTRACT FROM AUTHOR]

Soil microbiome play very important role in development of soil profile and implementation of soilbiochemical processes, especially for initial stages of soil regeneration after strong antropogenic impact. The developing soils of postmining landscape of Central Yamal (Russia, Yamal demi-island) and soil microbiome composition was investigated for the first time by use metagenomic approaches.The study includes sampling from heaps of abandoned mines of chromatic ore and sand quarries, reclaimed sand heap and mature larch forest as a reference. We analyzed several agrochemical parameters (pH, C- and N-content, basal respiration and other) and microbial community structure, measured quantitatively by RT-PCR and qualitatively by use high-throughput sequencing of 16s rRNA gene sequence libraries.Investigated soils showed low content of organic carbon and total nitrogen. Soil regeneration and soil basal respiration rate were considered as slow for tundra and forest tundra zones, which indicates the low level of soil microbiological activity. The highest total content of bacteria, acrchaea and fungi was revealed for soils of sandy and clay texture heaps and reclaimed soils. Reclamation practice result in sharp increasing of bacteria, archaea and fungi counts. At the same time, reclaimed soils showed the lower values diversity indexes in comparison with soils of abandoned mines.In taxonomic analysis composition of microbiomes that were revealed, many taxa was described previously as dominant groups in different cold environments, including alpine soils. Among them are Chthoniobacteraceae, bacteria from order Ellin 6513, Koribacteriaceae, Gaiellaceae and other.This work was supported by the Russian Scientific Foundation projects 17-16-01030, 'Soil biota dynamics in chronoseries of post-technogenic landscapes: analyses of soil ecological effectiveness of ecosystems restoration'. [ABSTRACT FROM AUTHOR]