Subsoil Material Research Articles

Avaliação da resistência e da deformação resiliente de quatro solos de subleitos rodoviários no estado do Rio Grande do Sul

O presente artigo apresenta o estudo do comportamento de quatro solos com origens geológicas diferentes, quanto à sua resistência e deformação resiliente, comumente empregados em subleitos rodoviários no estado do Rio Grande do Sul. A metodologia aplicada consistiu em ensaios de caracterização física e mecânica, obtenção da curva característica dos solos, além de simulações numéricas assistidas por dois programas computacionais: AEMC e AASHTOWare Pavement ME Design. Os resultados indicaram que os limites descritos em norma para utilização dos solos como material de subleito foram satisfeitos. Verificou-se que uma variação de ± 2% no teor de umidade provocou considerável alteração na resistência desses materiais, evidenciando a influência da sucção na resistência ao cisalhamento dos solos. As análises mecanicistas permitiram constatar a limitação do método de dimensionamento do DNIT, principalmente no que tange à ruptura por fadiga, além de destacar a importância do módulo de resiliência no comportamento da estrutura como um todo.

Using spectrocolourimetry to trace sediment source dynamics in coastal catchments draining the main Fukushima radioactive pollution plume (2011–2017)

Spectrocolourimetric measurements provide a relatively inexpensive, quick and non-destructive alternative to the analysis of geochemical and organic matter properties. When used in the analysis of sediments and their potential sources, these colour parameters may provide important information on the dominant processes (i.e. erosion) occurring in the Critical Zone. Here, they are used to investigate whether eroded sediment is derived from forest (i.e. natural), cultivated (i.e. anthropogenic) or subsoil sources in order to assess their potential to monitor the effect of decontamination in regions impacted by fallout from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Fifteen spectrocolourimetric properties (L*, a*, b*, C*, h, x, y, z, L, a, b, u*, v*, u’, v’) were measured in potential source (n = 37) and sediment (n = 400) samples collected during 13 campaigns from 2011 to 2017 after major flood events in two catchments (total surface area of 450 km2) draining the main FDNPP radioactive pollution plume. Potential sources included topsoil from forest and cultivated sources along with subsoil material originating from landslides, channel banks and the decontamination of cultivated areas. The optimum set of parameters used in the mixed linear model to calculate the sediment source contributions was obtained through the use of a range test, the Kruskal–Wallis H test and a linear discriminant analysis. Nine selected colour parameters correctly classified 100% of the source samples (i.e. forest, subsoil and cultivated sources). The results illustrate that cultivated landscapes were the main source of sediment to these river systems (mean 56%, SD 34%) followed by subsoil (mean 26%, SD 16%) and forest sources (mean 21%, SD 24%). However, these contributions varied strongly over time, with a peak of subsoil contributions (mean 57%, SD 17%) in Fall 2015, coinciding with the occurrence of a typhoon after the remediation works. These results were consistent with monitoring studies conducted in the same area that showed the major impact of typhoon Etau in September 2015 on sediment and radiocaesium fluxes. These original results demonstrate that spectrocolourimetric measurements may contribute to the routine monitoring of the effectiveness of remediation works in this post-accidental context. Owing to the inexpensive, rapid and non-destructive analyses, spectrocolourimetric-based tracing methods have significant potential to provide information on the dominant erosion processes occurring in the Critical Zone.

Deep soil flipping increases carbon stocks of New Zealand grasslands.

Sequestration of soil organic carbon (SOC) has been recognized as an opportunity to off‐set global carbon dioxide (CO2) emissions. Flipping (full inversion to 1–3 m) is a practice used on New Zealand's South Island West Coast to eliminate water‐logging in highly podzolized sandy soils. Flipping results in burial of SOC formed in surface soil horizons into the subsoil and the transfer of subsoil material low in SOC to the “new” topsoil. The aims of this study were to quantify changes in the storage and stability of SOC over a 20‐year period following flipping of high‐productive pasture grassland. Topsoils (0–30 cm) from sites representing a chronosequence of flipping (3–20 years old) were sampled (2005/07) and re‐sampled (2017) to assess changes in topsoil carbon stocks. Deeper samples (30–150 cm) were also collected (2017) to evaluate the changes in stocks of SOC previously buried by flipping. Density fractionation was used to determine SOC stability in recent and buried topsoils. Total SOC stocks (0–150 cm) increased significantly by 69 ± 15% (179 ± 40 Mg SOC ha‐1) over 20 years following flipping. Topsoil burial caused a one‐time sequestration of 160 ± 14 Mg SOC ha‐1 (30–150 cm). The top 0–30 cm accumulated 3.6 Mg SOC ha‐1 year‐1. The chronosequence and re‐sampling revealed SOC accumulation rates of 1.2–1.8 Mg SOC ha‐1 year‐1 in the new surface soil (0–15 cm) and a SOC deficit of 36 ± 5% after 20 years. Flipped subsoils contained up to 32% labile SOC (compared to <1% in un‐flipped subsoils) thus buried SOC was preserved. This study confirms that burial of SOC and the exposure of SOC depleted subsoil results in an overall increase of SOC stocks of the whole soil profile and long‐term SOC preservation.

Environmental DNA provides information on sediment sources: A study in catchments affected by Fukushima radioactive fallout

An excessive supply of sediment is observed in numerous rivers across the world where it leads to deleterious impacts. Information on the sources delivering this material to waterbodies is required to design effective management measures, and sediment tracing or fingerprinting techniques are increasingly used to quantify the amount of sediment derived from different sources. However, the current methods used to identify the land use contributions to sediment have a limited discrimination power. Here, we investigated the potential of environmental DNA (eDNA) to provide more detailed information on the plant species found in sediment source areas as a next generation fingerprint. To this end, flood sediment deposits (n = 12) were collected in 2017 in two catchments impacted by the Fukushima radioactive fallout along differing river sections draining forests, cropland or a mix of both land uses. Conventional fingerprints (i.e. fallout radionuclides and organic matter properties) were also measured in these samples. The conventional fingerprint model results showed that most sediment samples contained a dominant proportion of subsoil material. Nevertheless, the eDNA information effectively discriminated the three above-mentioned groups of sediment, with the dominance of tree, shrub and fern species in sediment sampled in rivers draining forests versus a majority of grass, algae and cultivated plant species in sediment collected in rivers draining cropland. Based on these encouraging results, future research should examine the potential of eDNA in mixed land use catchments where the contribution of topsoil to sediment dominates and where the cultivation of land has not been abandoned in order to better characterize the memory effect of eDNA in soils and sediment.

Ambient geochemical baselines for trace elements in Chernozems\u2014approximation of geochemical soil transformation in an agricultural area

The legal regulatory/action levels of trace elements in soils are established at high concentrations, at which the crucial functions of soil are at risk or are eliminated. However, concentrations below these action levels, but above presumed natural levels, may also limit particular ecosystem services, including organic food production. Thus, defining the (ambient) background concentrations is an essential part of environmental or health risk assessment, e.g., on Chernozems, which are considered to be the most productive soils and ones that should be protected against all forms of contamination. Based on 28 profiles of chernozemic soils developed from loess in an agricultural region of SW Poland presumed to be free of industrial contamination, ambient geochemical baselines have been derived for Fe and six trace metals for four standardized soil layers, including the topsoil (plow layer) and parent material layers. The median values for the plow layer (1.89% for Fe, and 537, 49, 17, 14, and 26 mg kg−1 for Mn, Zn, Pb, Cu, and Ni, respectively) are lower than the values reported for other Chernozems in SE Poland/Europe/the world, and thus may serve as a general geochemical baseline for chernozemic soils developed from loess. The concentration of Cd, although lower than in other Chernozems around the world, is higher than in Ukrainian Chernozems and thus may serve as a local (or Central European) baseline only. The median concentrations of Fe, Cu, Mn, and Zn are very close to their concentrations in the Chernozem buried under the Neolithic kurgan. However, Pb and Cd concentrations are two times higher than in the buried soil, indicating the scale of general contamination of the topsoil horizons of arable soils. Concentrations of the elements under study, excluding Fe, in both the buried and surface soils are significantly higher in the topsoil layer compared to parent material (loess), and this justifies the separate baseline values for topsoil horizons, instead of background values derived universally for parent rock types. This is essential, in particular in soils texturally differentiated within profiles, where the subsoil material has a different origin and cannot be considered the parent material for topsoil horizons. Underlying or locally outcropped bedrock (e.g., serpentinite rocks) may naturally enhance the total concentration of trace elements in the entire soil profile by the addition of metal-rich regolith particles during the formation of surface covers, e.g., by eolian processes under periglacial conditions (Late Pleistocene). Such soils are naturally enriched with metals (with nickel in the case of serpentinite bedrock), cannot be considered contaminated, and thus require a separate legal treatment, including separate (or individually suited) background baselines for health risk assessments.

Morphometric analysis and sub-watersheds prioritization of Nagmati River watershed, Kutch District, Gujarat using GIS based approach

AbstractMorphometric analysis of any watershed and its prioritization is one of the important aspects of planning for implementation of management programmes. Present study evaluates the quantitative morphometric characteristics of Nagmati River watershed in Kutch District of Gujarat by utilizing Cartosat-1 data (CartoDEM). In all 19 aerial and 6 linear morphometric parameters of the watershed have been evaluated. Drainage map of the study area reveals a dendritic drainage pattern with sixth order stream network comprising 492 numbers of streams and confining an area of 129.41 km2. Mean bifurcation ratio (Rb) and stream length ratio (RL) of the watershed evaluated are 3.44 and 0.54 respectively which corroborates the fact that drainage pattern is not influenced by the geological evolutions and disturbances in the recent past. The drainage density of 2.68 kmꞏkm−2 indicates impermeable subsoil material with sparse vegetation and moderate to low relief. Elongation ratio of 0.956 infers the basin to be closer to a circular shape. The geologic stage of development and erosion proneness of the watershed is quantified by hypsometric integral (HI) bearing value as 0.5, indicating the landscape to be uniform and in early mature stage. The study prioritizes eight sub-watersheds as high, medium and low for taking up soil and water conservation activities. Hence, remote sensing applications proved to be highly useful in extracting the precise data for the evaluation and analysis of watershed characteristics.

Assessment of silt from sand and gravel processing as a suitable sub-soil material in land restoration: A glasshouse study

Annually, sand and gravel processing generates approximately 20 million tonnes of non-commercial by-product as fine silt particles (<63 μm) which constitutes approximately 20% of quarry production in the UK. This study is significant as it investigated the use of quarry silt as a sub-soil medium to partially substitute soil-forming materials whilst facilitating successful post-restoration crop establishment. In a glasshouse pot experiment, top-soil and sub-soil layering was simulated, generating an artificial sub-soil medium by mixing two quarry non-commercial by-products, i.e. silt and overburden. These were blended in three ratios (100:0, 70:30, 50:50). Pots were packed to two bulk densities (1.3 and 1.5 g cm-3) and sown with three cover crops used in the early restoration process namely winter rye (Secale cereale), white mustard (Sinapis alba) and a grassland seed mixture (Lolium perenne, Phleum pratense, Poa pratensis, Festuca rubra). Three weeks into growth, the first signs of nitrogen (N) deficiency were observed in mustard plants, with phosphorus (P) and potassium (K) deficiencies observed at 35 days. Rye exhibited minor N deficiency symptoms four weeks into growth, whilst the grassland mixture showed no deficiency symptoms. The 70:30 silt:overburden sub-soil blend resulted in significantly higher Root Mass Densities of grassland seed mixture and rye in the sub-soil layer as compared with the other blends. The innovation in this work is the detailed physical, chemical and biological characterisation of silt:overburden blends and effects on root development of plants commonly used in early restoration to bio-engineer soil structural improvements.

Daytime Surface Energy Fluxes over Soil Material Remediated Using Thermal Desorption

Core Ideas Surface energy balance was quantified with micro‐Bowen ratio instrumentation. Surface energy balance was similar over native topsoil and soils treated with thermal desorption. Thermal desorption did not alter soil temperature dynamics or evaporation. A mix of topsoil and thermal desorption–treated soil matched surface energy balance of topsoil best. Remediation efforts to reduce contaminant concentrations in soils often alter soil properties. Since these alterations can affect the capacity of soil to function, their extent and magnitude may dictate future land use. This study addresses the suitability of soils for agricultural production after remediation of petroleum hydrocarbons using ex situ thermal desorption by quantifying the daytime surface energy balance prior to the growing season. The energy balance was quantified using micro‐Bowen ratio instrumentation to compare non‐contaminated topsoil (A) to both subsoil materials treated by thermal desorption (TD) and a 1:1 mixture (v/v) of TD and A (TDA). Despite differences in soil characteristics, the net radiation, soil heat flux, latent heat flux, and sensible heat flux were each similar among the three reclamation conditions over a period of 18 d. The fluctuations in these fluxes between the three conditions were attributed to natural variability, and they were not large enough to induce apparent inconsistencies in soil temperature dynamics or evaporative losses. Overall, these findings suggest the surface energy balance in thermal desorption–treated soils is similar to that of the native topsoil and that using a mixture of treated soils with native topsoil may even be a better representation of pre‐disturbance conditions.

CONTRIBUCIÓN DE LAS FRECUENCIAS CARACTERÍSTICAS AL PERIODO DE VIBRACIÓN DOMINANTE EN LA CIUDAD DE QUERÉTARO, MÉXICO

En este trabajo se presenta la metodología desarrollada para evaluar la contribución de la frecuencia característica de cada estrato al período fundamental de vibración a partir de la inversión de las curvas de dispersión aparente obtenidas del levantamiento en campo de ondas superficiales con fuente activa, sin importar la velocidad de cada capa. El cálculo del período fundamental se realizó con el procedimiento simplificado de un medio estratificado lineal desarrollado por Dobry et al. (1976). Como referencia para la clasificación por clases o categorías de velocidades se utilizó el elaborado por el International Building Code (IBC, 2009) y modificado para los materiales del subsuelo de la Ciudad de Querétaro. Las unidades geológicas principales se agruparon en tres secuencias estratigráficas: la Rocosa que abarca las mesetas y elevaciones topográficas que rodean el valle, la de Ladera que es la zona de pendiente variable constituida por depósitos volcánicos y sedimentarios (aluviales), y la secuencia de Planicie que comprende depósitos estratificados del tipo lacustre, fluvial y volcánico. A partir del análisis de los perfiles de velocidades de ondas de corte se observó que existen estratos con velocidades bajas confinados por otros de alta velocidad; lo que indica la presencia de estratos de baja rigidez a profundidades variables. En la zona rocosa el período fundamental de vibración es corto (menor que 0.1 s), mientras que en los depósitos de la planicie es más largos (mayor que 0.3 s). En la zona de ladera el período es relativamente largo (variable entre 0.1 s a 0.3 s) posiblemente debido a un efecto topográfico. Los resultados obtenidos muestran que la metodología propuesta para evaluar el período dominante a partir de la integración de las frecuencias características obtenidas con ondas superficiales permite estimar los espesores y velocidades de corte de cada estrato, el periodo fundamental de vibración de cada secuencia estratigráfica y finalmente, sus espectros de sitio.

A large-scale soil-mixing process for reclamation of heavily disturbed soils

Soil excavation associated with energy production or mineral extraction results in heavily disturbed landscapes that must be reclaimed to avoid long-term economic and environmental losses. A common practice in reclamation of these sites is topsoil replacement across the disturbed area. In some instances, this process requires importing topsoil from another location, known as topsoil transfer, which can be expensive and introduce a new seedbank, insect community, or plant pathogens. This research describes a soil-mixing process for disturbed soils that may be used to reduce costs associated with topsoil transfer and accelerate the recovery of soil function following a large excavation. This process was applied to two disturbed soils: i) crude-oil contaminated subsoil material; and ii) crude-oil contaminated subsoil material that was remediated using ex-situ thermal desorption. These soils were separately mixed with native, non-contaminated agricultural topsoil at 1:1 ratio (by volume). The native, disturbed, and mixed soils were characterized for soil physical, chemical, and biological properties, and statistics indicated that the mixtures were homogenous both spatially and with depth. However, the mixtures were significantly different from both the disturbed materials and native topsoil, primarily driven by changes in soil organic carbon, plant available nutrients, and biological activity. These results suggest that this mixing process can be used for soil reclamation at large-scale excavation sites to both reduce project costs and enhance recovery of soil parameters.

Phosphate Speciation and Citrate-Induced Mobilization of P in an Acric Oxisol

ABSTRACTBillions of dollars are spent annually in Brazil on imported phosphorus (P) fertilizers for agricultural crops produced on Oxisols. Phosphate fixation by Oxisols is a main limitation to crop productivity because these highly weathered soils have a high phosphate adsorption capacity. The objective was to determine whether reaction of an Acric Oxisol with citrate increases P availability. Columns of P-amended subsoil material were leached with 1 mM citrate solution, and effluent was monitored. Solid-phase speciation was measured for different stages of leaching using X-ray absorption near edge structure (XANES) spectroscopy at the P K-edge. When soil columns were leached with up to 56 column pore volumes of 1 mM citrate solutions, no P was detected in column effluent samples, whereas aluminum (Al) and iron (Fe) increased up to 30 and 1.4 µmol L−1, respectively. The XANES analysis suggested that with increased leaching, a minor proportion of phosphate adsorbed on Fe-oxides increased as phosphate adsorbed on Al-oxides decreased. The results indicated that citrate tends to induce minor species redistribution of phosphate between Al- and Fe-oxide bound forms, but P mobilization was trivial compared with complexometric mobilization of Fe and Al.

Rapid understory plant recovery following forest floor protection on temporary drilling pads

AbstractOil sands exploration fragments the boreal landscape by constructing numerous drilling pads to assess underground petroleum reserves. Reclamation of these pads is challenging and slow, particularly for forest understory species. We investigated the feasibility of accelerated forest understory restoration on these temporary pads by taking advantage of the propagule bank and clonal regeneration strategy of many boreal plants. We covered and protected the forest floor (FF) with subsoil during winter pad construction. This forest floor protection (FFP) method was then compared with the current practice of stripping off, stockpiling, and then replacing the FF during the reclamation phase (rollback, RB) and to conventional clearcut (CC) harvesting. In the first growing season, surface disturbance as well as richness and cover of plant regeneration was evaluated; vegetation assessment was repeated in the fifth growing season. Although there were some slight differences between the communities in the FFP and CC treatments, likely associated with varying levels of residual slash and subsoil material, there were striking differences between the communities in the RB and FFP treatments. In addition, while establishment of deciduous tree species was similar between the FFP and CC treatments, there were very few trees found in the RB treatment. The study indicates that protection and careful uncovering of the FF during temporary drilling pad construction should be a technique of choice for forest reclamation used in the boreal forest. However, as RB will still play a part in the reclamation of these sites, management intervention will be required to achieve reclamation goals.

Scales of Water Retention Dynamics Observed in Eroded Luvisols from an Arable Postglacial Soil Landscape

Core Ideas Hysteretic, seasonal, and interannual soil water retention dynamics were identified. Hydraulic functions for each drying and wetting event were described separately. Shorter term dynamics indicated soil structural and wettability changes. Longer term dynamics reflected soil management and erosion history. For each timescale, different processes control water retention dynamics. Soil water retention is frequently described by unique main drying curves measured in the laboratory on intact soil cores. In the field, however, soil pore structure changes as a result of swelling and shrinkage, wetting and drying, or tillage operations. For erosion‐affected arable soils characterized by truncated profiles, water retention dynamics could be even more complex. The objective of this study was to separate shorter term hysteretic from longer term seasonal dynamics in field‐measured water retention data of eroded Luvisols. Soil water content and matric potential data were from tensiometers and time‐domain reflectometry sensors of six lysimeter soil monoliths from two sites. For 2012 through 2014, drying and wetting periods were identified and fitted with the van Genuchten (VG) retention function. The results confirmed that drying water retention curves were steeper than those obtained in the laboratory. Steepness increased and fitted VG parameter values of saturated water content decreased within seasons, indicating that rewetting rates successively declined after each dry–wet cycle. Drying water retention curves returned to a similar level in each spring except for soils of transferred monoliths, where drying water retention tended to increase. Results suggested that water retention dynamics of eroded Luvisols was affected by continual incorporation of subsoil material in the Ap horizon and crop management practices in addition to hysteresis and seasonal dynamics. The disentangling of dry–wet cycles from time series of soil water content and matric potential was found useful for identifying the processes responsible for water retention dynamics and could eventually help improve flow and transport models.

CRESCIMENTO, NUTRIÇÃO E QUALIDADE DE MUDAS DE Pouteria garderiana (A. DC.) RADLK. PRODUZIDAS EM SUBSTRATOS ORGÂNICOS

RESUMO Este estudo foi conduzido para averiguar o uso de substratos orgânicos na produção de mudas nativas do Cerrado brasileiro. O objetivo foi avaliar os parâmetros biométricos, nutrição e qualidade de mudas de guapeva (Pouteria gardneriana) produzidas em substratos contendo diferentes fontes de matéria orgânica. Utilizaram-se os seguintes componentes para a formulação dos substratos: subsolo (SB), casca de arroz (RH), composto de esterco bovino [CC (silagem de milho + esterco bovino)], esterco bovino (CM), bagaço de cana (CB), torta de filtro de cana (FC) e BioPlant (BP). Cinco substratos foram formulados utilizando proporções em base de volume, como segue: SB+RH (1:1, v/v), SB+CC (1:1, v/v), SB+CM (3:1, v/v), CB+FC (3:2, v/v) e BP. Avaliou-se o comprimento do caule, o diâmetro do colo radicular, o peso seco da raiz, o peso seco da parte aérea, a nutrição e o índice de qualidade Dickson. A utilização do CM como fonte de matéria orgânica proporcionou, em geral, os melhores resultados para as características biométricas e a produção de matéria seca. O uso de matéria orgânica nos substratos SB+CM (3:1, v/v) e SB+CC (1:1, v/v) melhorou a qualidade do solo e favoreceu o crescimento e qualidade das mudas de guapeva, e podem ser indicados como substratos alternativos.

Deep ploughing increases agricultural soil organic matter stocks.

Subsoils play an important role within the global C cycle, since they have high soil organic carbon (SOC) storage capacity due to generally low SOC concentrations. However, measures for enhancing SOC storage commonly focus on topsoils. This study assessed the long-term storage and stability of SOC in topsoils buried in arable subsoils by deep ploughing, a globally applied method for breaking up hard pans and improving soil structure to optimize crop growing conditions. One effect of deep ploughing is translocation of SOC formed near the surface into the subsoil, with concomitant mixing of SOC-poor subsoil material into the 'new' topsoil. Deep-ploughed croplands represent unique long-term insitu incubations of SOC-rich material in subsoils. In this study, we sampled five loamy and five sandy soils that were ploughed to 55-90cm depth 35-50years ago. Adjacent, similarly managed but conventionally ploughed subplots were sampled as reference. The deep-ploughed soils contained on average 42±13% more SOC than the reference subplots. On average, 45years after deep ploughing, the 'new' topsoil still contained 15% less SOC than the reference topsoil, indicating long-term SOC accumulation potential in the topsoil. In vitro incubation experiments on the buried sandy soils revealed 63±6% lower potential SOC mineralisation rates and also 67±2% lower SOC mineralisation per unit SOC in the buried topsoils than in the reference topsoils. Wider C/N ratio in the buried sandy topsoils than in the reference topsoils indicates that deep ploughing preserved SOC. The SOC mineralisation per unit SOC in the buried loamy topsoils was not significantly different from that in the reference topsoils. However, 56±4% of the initial SOC was preserved in the buried topsoils. It can be concluded that deep ploughing contributes to SOC sequestration by enlarging the storage space for SOC-rich material.

Radical soil management for Australia: A rejuvenation process

Particularly in the Australian context, this concept paper argues that much of the continent has highly weathered soil of great antiquity with poor agricultural productivity, that much younger soil also exists in juxtaposition, and that certain anthropogenic processes, such as soil inversion or any other radical soil management, can rejuvenate soil for increased productivity. Younger soil occurs wherever there is an accumulating environment where relatively young materials are being deposited (e.g., alluvium), or eroding circumstances where less weathered materials become exposed such as following colluvial or deflation activity. Depositional materials are not necessarily younger when they result from redistribution of highly weathered materials such as by aeolian activity. Certain soil types may be considered as self-rejuvenating if they exhibit self-mulching and pedoturbation characteristics whereby less weathered subsoil material is brought up into the soil. Soil rejuvenation events, through a variety of processes, therefore occur naturally in Australia, as they do elsewhere. With respect to wheat production for illustrative purposes, it is argued that young or rejuvenated soil is more agriculturally productive, and that certain anthropogenic processes (such as the addition of clay or bringing subsoil clay to the surface) that rejuvenate soil can be brought about by radical soil management.

Depth to compact subsoil effects on soil properties and barley–potato yields on a loamy soil in New Brunswick

Rees, H. W., Chow, T. L., Xing, Z., Li, S., Monteith, J. O. and Stevens, L. 2015. Depth to compact subsoil effects on soil properties and barley–potato yields on a loamy soil in New Brunswick. Can. J. Soil Sci. 95: 203–218. An experiment was established to investigate the implications of thickness of soil over compact subsoil on plow layer soil thermal and water regimes and ultimately the yield of potato (Solanum tuberosum L.) and barley (Hordeum vulgare L.). Three depths were considered, 24 cm (shallow), 36 cm (medium) and 60 cm (deep). Results on soil temperature impacts were inconclusive. The shallow treatment water content was most greatly affected by precipitation and had the greatest potential to become saturated then drying out more than the other treatments. The deep treatment did not improve soil temperature and water regimes enough to increase crop yield. The medium depth, which most closely approximated existing local solum development, proved superior to the shallow treatment in terms of crop yield and reduced soil moisture variation, while the deep treatment did not warrant the effort required to create under field conditions. Barley and potato yields from the medium depth were greatest with 20% (significant) and 8% (not significant) more yield, respectively, than from the shallow treatment. The eroded soil profiles common to the New Brunswick potato belt exacerbate soil erosion since an eroded soil has less volume to accept water from a rainfall event, making the soil more prone to erosion, especially if it is true that our weather is changing, with the amplitude of weather shifts becoming greater. Incorporation of subsoil materials into the plow layer of eroded soils due to soil loss may result in further reduction in crop yield.

MORPHOLOGY AND GENESIS OF GILGAI

Gilgai morphology, genesis, distribution and role in the landscape are described on the base of literature data and personal investigations. Gilgai is a specific type of microrelief, formed by slow uplift and intrusion of a subsoil material due to soil heaving resulted from alternating drying and wetting. In terms of genetic classification of landforms gilgai could be classified as hydrogenic microrelief, along with cryogenic, karst and suffosion microrelief. Gilgais may be identified and distinguished from other types of microrelief by the presence of slickensides – slip planes demonstrating the direction of the vertical and lateral shearing. Gilgai are mostly presented in tropical and subtropical regions, but were also found in Russia and the former USSR.

Catchment delineation and morphometric analysis using geographical information system.

The geographical information system (GIS) has emerged as an efficient tool in delineation of drainage patterns of watershed planning and management. The morphometric parameters of basins can address linear, areal and relief aspects. The study deals with the integrated watershed management of Baliya micro-watersheds, located in the Udaipur district of Rajasthan, India. Morphometric analysis in hydrological investigation is an important aspect and it is inevitable in the development and management of drainage basins. The determination of linear, areal and relief parameters indicate fairly good significance. The low value of the bifurcation ratio of 4.19 revealed that the drainage pattern has not been distorted by structural disturbance. The high value of the elongation ratio (0.68) compared to the circulatory ratio (0.27) indicates an elongated shape of the watershed. The high value of drainage density (5.39 km/km(2)) and stream frequency (12.32) shows that the region has impermeable subsoil material under poor vegetative cover with a low relief factor. The morphometric parameters of relief ratio (0.041) and relative relief (0.99%) show that the watershed can be treated using GIS techniques to determine the morphometric presence of dendritic drainage pattern, with a view to selecting the soil and water conservation measures and water harvesting.

Applications of shallow-seismic exploration methods for mechanical characterization of soil and rock bodies at engineering project sites in Colombia

The application of seismic methods for rock and soil-mass characterization has proved to be useful for engineering projects of any kind. These methods can predict the presence and geometry of low-competent subsoil materials and can define preliminary structural designs for each project. In three studies in Colombia, refraction tomography and multichannel analysis of surface waves (MASW) were applied for road tunnels and multistory building construction, respectively. In situ rock and soil types were classified based on P- and S-wave measurements, and preliminary structural designs and construction methods were recommended for each case. Both rock and soil classifications and preliminary structural designs must be refined with direct subsoil-characterization methods such as core drilling and laboratory testing.