Shale Soil Research Articles

Determination of Phosphorous Fixation Capacity on Alluvium, Sandstone and Shale Soils of Akwa Ibom State, Nigeria

The study was aimed to determine the fixation capacity of phosphorous from three parent materials (Alluvium, Shale and Sandstone) in Akwa Ibom State. A composite soil samples were collected from three representative locations. A treatment solution containing 0, 20, 40 and 80mgl-1 of P prepared from KH2PO4 were added to 20g of soil samples in a cups and incubated for 1, 7, 30 and 60 days. The design was 3 x 4 factorial experiment (3 soil types and 4 rates of P) were fitted into Completely Randomized Design (CRD) with three replications. At a set day, the exchangeable and water soluble P were extracted with Bray P – 1 extractant and P not extracted was considered fixed in the soils. The results revealed that the soils were fertile and moderately acidic and than the amount of phosphorous fixed in shale and alluvium soils, decrease with length of incubation and a significant higher fixation were observed in day 1 (60.6 mgkg-1 shale and 50.6mgkg-1 in alluvium). The amount observed in sandstone increased with the length of incubation and a significant amount fixed was observed in 30 days (54.4mgkg-1). The study also revealed that the concentration of P fixed increased with increasing rates of P added in all the soils. Base on the inherent fertility of the soils, the use of crop rotation and organic manure is recommended to maintain its fertility for high productivity.

Vertical distributions of organic carbon fractions under paddy and forest soils derived from black shales: Implications for potential of long-term carbon storage

Black shales are characterized by a high content of organic carbon (C). Few studies have focused on the influence of land use on soil organic C (SOC) fractions from soils derived from black shale (black shale soils). The objective of this study was to elucidate the influence of land use on SOC fractions in black shale soils combining chemical determination and stable C isotope analysis techniques. Herein, we determined labile organic C (LOC), semi-labile organic C (Semi-LOC), and recalcitrant organic C (ROC) fractions in various depths of soils in paddy fields (0–70 cm) and forests (0–120 cm) from black shale distribution region in Hunan province, China, and then investigated δ13C values of these soils. Results showed that the contents of LOC, Semi-LOC, and ROC in paddy soils (1.63–7.35 g kg−1, 0.35–1.21 g kg−1, and 3.75–14.8 g kg−1, respectively) and forest soils (0.73–4.94 g kg−1, 0.12–0.89 g kg−1, and 1.44–8.96 g kg–1, respectively) are significantly decreased with increasing depth. The contribution made by LOC to SOC in paddy soils was significantly lower than that in forest soils, while the contribution made by ROC to SOC was significantly higher in paddy soils than that in forest soils. In these two land uses, the δ13C values were higher in SOC compared to the ROC fraction, while the δ13C values were close in the ROC fraction below 20 cm soil depth. Our study indicated that i) new C is mainly limited to the surface soil layer (0–10 cm) in forests, while it can be leached along the soil profiles in paddy fields; ii) the estimated ROC pool is ~900 Pg within the 0–100 cm soil layer in terrestrial ecosystems, which should better represent the ability of soil C sequestration.

Cementation of Shale Soils by MICP Technology and Its Damage Characteristics Due to Freeze–Thaw Weathering Processes

Abstract This paper describes an application for microbial induced calcite precipitation (MICP) on the cementation of shale soils for ground reinforcement in cold regions. The micro and macrostruct...

Repairment of clay shale soil by stabilization method using a cement binder

Clay shale is a type of clay that is easy to expand when it comes into contact with water because of the montmorillonite clay mineral it contains. The effect of water also causes a decrease in strength in the clay shale. As a result of the clay shale behavior, some buildings become damaged or landslides occur on the slope. The soil stabilization method with a cement binder is one solution to improve the detrimental properties of the clay shale. The selected cement content variations are 20, 30, and 40%. Cement Water Factor 35% for all variations. Laboratory testing is carried out at 0, 7, 14, and 21 days. Tests carried out in the form of specific gravity, swelling, atterberg limits, unconfined compressive, cation exchange capacity, X-Ray Difraction (XRD), and Scanning Electron Mycroscope (SEM). Tests show that the most optimum mixture is 30% clay shale-cement (CS-C30). CS-C30 produces changes in clay shale parameters including an increase in compressive strength without any decrease, and a reduction in the expansive nature as indicated by the decrease in the value of swelling pressure, and cation exchange capacity. Changes in these parameters are suspected because it already does not contain montmorillonite in CS-C30 based on XRD.

Soils Developed from Dolomitic Shale in the Yichang Area, China and Adsorption Characteristics for Phenol

Recently, the problem of phenolic organics pollution has become increasingly serious. More and more strategies have been developed to remove phenolic organics from water, including oxidation, adsorption, chemical precipitation, etc. Among them, adsorption technology has attracted great attention due to its advantages of high efficiency, simplicity and easy operation. In this study, the natural shale soil without any modification was directly used as adsorbent to remove phenol from aqueous solutions. The shale soil samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption-desorption isotherms. Detailed kinetics and isotherm studies of phenol adsorption onto shale were investigated. According to the results of the orthogonal test, the influence degree of the four factors on the removal of phenol by soil samples was operating temperature > adsorbent dosage > contact time > pH. The adsorption kinetics of phenols by the soil corresponded with the pseudo-second-order kinetic model. Thermodynamic studies indicated that Freundlich adsorption isotherm model could better describe phenol removal characteristics than Langmuir adsorption isotherm model. And the maximum adsorption capacity was found to be 9.68 mg/g for phenol. It is concluded that shale soil without any modification or activated methods could be employed as a low-cost alternative adsorbent for wastewater treatment.

Performance Evaluation of Forage Ash Stabilized Shale Soil for Effective Use in Flexible Pavement

For most developing countries, infrastructural development, especially in the road sector, plays a key role in its development, however geotechnical engineers encounter lots of problem during the construction of most roads especially when the subgrades consists of expansive soils due to their swelling and shrinkage problems which are responsible for potholes, cracking and undulations in the pavement leading to discomfort and lessening the life of vehicle, hence the engineering properties of these soils needs to be improved. Preliminary tests which include specific gravity, atterberg’s limits test, grain size analysis, compaction tests, California bearing ratio test and unconfined compressive tests were carried out the shale samples, after which 2 to 20% by weight of forage ash was added to the shale sample and subjected to Atterberg’s limits test and some strength tests (Compaction, California Bearing Ratio, and Unconfined Compressive Test). The results show that the addition of forage ash increased the plasticity index of the shale sample, however, the California bearing ratio (CBR) values (soaked and unsoaked) were significantly increased both at the West African level and Modified AASHTO level. The maximum dry density (MDD) of the sample was increased as well as a reduction of the Optimum Moisture Content (OMC) of the sample was found. The values of the unconfined compressive strength show that there was also an increase in the strength of the sample. In conclusion, forage ash was found to be an effective additive for shale soil stabilization and improves the strength of the soil.

Composition of Smectite from Maastrichtian Sediment of the Afikpo Basin, southeast Nigeria

The sand, silt, shale and clay fractions soils derived from Maastrichtian sediments in the Afikpo Basin, southeastern Nigeria exhibit unusually high cation-exchange capacities. Smectite was identified by X-ray diffraction in all sample fractions and was selectively dissolved by treatment with 1HCl and 0.5 NaOH. Structural formulae, based on chemical analysis of the dissolved material, suggest that the smectite is intermediate in composition between a di- and a trioctahedral mineral and that the octahedral cation occupancy, together with the number of Mg and Fe atoms per unit cell, decreases with decrease in particle size of the soil fraction examined. The mean formula for the smectite in the clay separate is: [(M + = 0.40, Si = 3.33, Al = 0.67), (Al = 1.07, Fe 2+ = 0.09, Fe 3+ = 0.41, Mg = 0.82)] O 10 (OH) 2 . Similar analysis of smectite present in clay-size material separate from weathered granitic rock taken from the bases of the soilprofiles showed that it had close to the full trioctahedral inherited from the weathered granites.The clay mineralogy of the soils was affected by inherited smectite, probably of hydrothermal of deuteric origin. This mineral is unstable in the soil environment and, although its alteration products are fairly uniform in composition. Keywords: Dissolution, Granitic, Octahedral, Smectite, Soil

Differential speciation and availability of copper in soils derived from different parent materials in Imo State, southeastern Nigeria

Effective and efficient management of copper (Cu) in soils for optimum crop production and environmental conservation depends on proper knowledge of the various copper forms and fractions in soils as well asparent material. The distribution of forms of Cu in soils of different parent materials (coastal plain sands, alluvium, false-bedded sandstones and Imo clay shale) in Imo State, Southeastern Nigeria was evaluated using sequential extraction procedure, comprising of six fractions; water soluble (WS), exchangeable (EX), specifically sorbed/CO3 bound (SSC), Fe-Mn bound (Fe-Mn), organic matter bound (OMB) and residual bound (RE) fractions. Soil was sampled at 0-15, 15-30, 30-45, 45-60 and 60-75 cm depths from each soil. Data obtained were subjected to analysis of variance and means separation was done by the procedure of Least Significant Difference at 5% probability level. Correlation analysis of the various Cu forms and some soil properties was also carried out. Results showed that the water soluble, specifically sorbed/carbonate bound, Fe-Mn bound, organic matter bound (OMB) and residual bound (RE Cu fractions differed significantly among the soils of the different parent materials. The Fe-Mn bound copper was the dominant fraction in most of the soils, contributing 41.53-46.63% to the total Cu, being highest in the alluvial soil (6.389 mg kg-1) and lowest in the Imo clay shale soil (2.231 mg kg-1). Moderate concentrations of available Cu (0.694-1.456 mg kg-1) were observed and significant differences were observed among the soils. Correlations among the different Cu forms (WS vs EX r - 0.48; EX vs Fe-Mn r −0.46) and some soil properties (OM vs Fe-Mn r −0.86; Ca vs RE r −0.59; Clay Vs Fe-Mn r −0.53) were determined.Key words: copper fractions, copper availability, parent materials, soil properties, southeastern Nigeria

不同类型土壤栽培对苦丁茶树叶片生长和光合特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同类型土壤栽培对苦丁茶树叶片生长和光合特性的影响 DOI: 10.5846/stxb201806111303 作者: 作者单位: 福建农林大学林学院,贵州大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 贵州省科技攻关项目（黔科合NY字[2007]3040号） Effects of different soil types on growth and photosynthetic characteristics of Ligustrum robustum Author: Affiliation: College of Forestry,Fujian Agriculture and Forestry University,College of Forestry,Guizhou University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究苦丁茶树叶片生长与光合特性对不同类型土壤栽培的响应特征，确定最适苦丁茶栽培的土壤类型，可为高产优质化的苦丁茶种植业及其规模化生产基地的建立提供科学依据。通过土壤栽培实验研究了不同类型的土壤对苦丁茶树叶片生长、叶片解剖结构、叶绿素含量和光合特性的影响。结果表明：石灰岩土壤栽培条件下，苦丁茶叶长和叶面积比其他6种土壤栽培下的显著提高了34%-57%和43%-68%，叶绿素总量显著增加9%-33%，叶片、上下表皮、海绵组织和栅栏组织的厚度均显著高于其他6种土壤栽培。不同类型土壤栽培下苦丁茶净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）和饱和蒸气压亏缺（Vpdl）的日变化趋势均呈单峰型，日均Pn和Tr值大小依次为：石灰岩 > 石英砂岩 > 玄武岩 > 长石石英砂岩 > 第四纪红色黏土 > 变余砂岩 > 煤系砂页岩，其中石灰岩土壤栽培下的日均Pn值相比其他6种土壤下的显著提高了13%-45%，且叶片最大净光合速率、表观量子效率、暗呼吸速率、光补偿点（LCP）和光饱和点（LSP）也最大，而煤系砂页岩栽培时最低，其LSP和LCP较石灰岩栽培的分别显著下降了40%和46%。综上，在7种类型的土壤中，石灰岩土壤栽培最有利于苦丁茶树叶片的生长发育、并促进叶绿素的合成和加强对光能的吸收利用，最终提高其叶片光合能力，其次为玄武岩土壤，而煤系砂页岩土壤是最不利于苦丁茶树叶片生长发育和光合作用。建议在苦丁茶种植业的发展和规模化生产基地建立时因选择由石灰岩性母岩发育的土壤进行栽培，从而提高苦丁茶的产量和品质。 Abstract:In this study, we investigated the effects of seven types of cultivation soil on leaf growth and photosynthetic characteristics of Ligustrum robustum (kuding tea) seedlings, aiming to provide scientific advices for cultivation and management of the species for cultivation and management of the species. We measured leaf length, width, area, spongy tissue thickness, palisade tissue thickness, layer of palisade tissue, chlorophyll content, and photosynthetic parameters of the seedlings grown in different soil types. The results showed that cultivation in limestone soil increased the length and area of the leaves by 34%-57% and 43%-68%, respectively, when compared with the other six soil types. In addition, leaf thickness, spongy tissue, and palisade tissue were significantly higher, and total chlorophyll content was 9%-33% higher in the limestone soil than in the other six soil types. The soil types did not affect the diurnal variation in net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and vapor pressure deficit (Vpdl). The daily average of Pn and Tr values in the seven soil types in descending order were as follows:limestone > quartz sandstone > basalt > feldspathic quartz sandstone > quaternary red clay > blastopsammite > coal sand shale. The daily average of Pn value was 13%-45% higher in limestone soil than in the other six soil types. Pn, Gs, and Tr were positively correlated, but they were negatively correlated with Vpdl. The maximum net photosynthetic rate, light saturation (LSP), light compensation (LCP), dark respiration rate, and apparent quantum yield were observed in limestone soil. LSP and LCP were significantly lower in coal sand shale soil (40% and 46%, respectively) than in the limestone soil. In summary, limestone soil is most beneficial for the growth and development of leaves. It can promote the production of chlorophyll and thus enhance the absorption and utilization of light energy and improve leaf growth and photosynthetic capacity. The second appropriate soil type is basalt. In contrast, coal sand shale soil is most unfavorable for the growth and development of leaves and photosynthesis. Therefore, limestone soil should be used for the large-scale plantation of L. robustum and improvement of the yield and quality of kuding tea. 参考文献 相似文献 引证文献

Rapid estimation of microbial biomass in acid red soils with and without substrate incorporation

A rapid and alternative measurement of microbial biomass in acid red soils with and without substrate incorporation is proposed for soil quality evaluation. Soil microbial biomass C (SMBC) and N (SMBN) in 24 typical red soil samples developed from two parent materials (granite and arenaceous shale) were measured using fumigation-extraction followed by dry combustion method in comparison with ultraviolet (UV) spectrophotometry (increase in absorbance at 280 nm, ΔUV280). The reliability of microbial biomass estimation by UV spectrophotometry was verified using six representative red soils amended with biochar (0, 1, 3 and 5%) and glucose (0, 100, 500 and 1000 mg kg−1) separately. ΔUV280 was strongly correlated with SMBC and SMBN measured by dry combustion, regardless of biochar/glucose incorporation. Validated conversion equations from unamended soil data were dependent on confounding effects of organic C and particle size and can be described as follows: SMBC = 27.08 × ΔUV280 (R2 = 0.67, n = 24) and SMBN = 3.62 × ΔUV280 (R2 = 0.69, n = 24). Regression models for rapid estimation of microbial biomass in red soils from different parent materials had to be calibrated separately in case of amendments. In most cases, SMBC (R2 of 0.75–0.76 and root mean square error (RMSE) of 22.2–29.3 mg kg−1) and SMBN (R2 of 0.74–0.80 and RMSE of 2.60–14.2 mg kg−1) can be predicted from ΔUV280 in biochar/glucose-amended soils using these equations. The slope of the regression of SMBC against ΔUV280 shifted in biochar-amended granite soils, mainly due to uncoordinated changes of SMBC in response to the difference in parent material-induced nutrient availability, while shifts of SMBC (or SMBN) against ΔUV280 in glucose-amended arenaceous shale soils were attributed to particle size distribution. Soil microbial biomass (SMBC and SMBN) in red soils can be rapidly predicted by fumigation-extraction with UV spectrophotometry detection and corresponding correction of calibration curves, depending on soil nutrient availability, particle size distribution and organic C levels.

Soil apatite loss rate across different parent materials

Apatite is a lithogenic soil mineral and the primary source of phosphorus (P) that limits crop production worldwide. Apatite differs with sediment geology, and soil processes redistribute the P forms. Whether soil apatite loss with soil formation differs in sediment needs further research. The objectives of this study were to (i) determine the relationship between soil genesis and the distribution of P fractions in soils formed in different parent materials, and (ii) determine the extent to which apatite loss rate with weathering differs due to parent material. Triplicate profiles for three soils representing sequences of development in loess, alluvium, shale residuum, and sandstone residuum were analyzed for various soil P forms and related parameters at genetic horizon levels. The labile P fractions, secondary phosphates of iron and aluminum, and apatite-P varied with parent materials and soil weathering. Apatite-P decreased exponentially with the sum of iron adsorbed and occluded P in soil, and fit the equation M(Y)=Mo[1-exp.(−λY)] where Mo is initial apatite-P in the sediment, M(Y) is the current apatite-P content in soil, Y is the cumulative iron sorbed P, and -λ, an empirical decrease-rate constant. The apatite loss model fits well for the all soils, except the shale soils that contained lithogenic iron oxides. At the Alfisols development stage, apatite-P loss was 48% in loess, 72% in sandstone and 93% in alluvium out of 1455, 675 and 945kgha−1 per 0.9m that arrived with the sediments, respectively. Fe-P50, the level of iron sorbed P content in soil, was 55.7 for loess, 46.8 for sandstone, and 20.4kgha−1 per 0.9m for alluvium, suggest the highest stability of apatite occurred in loess. The model provides a measure to compare kinetics of soil apatite dissolution under soil genesis independent of time in term of weathering.

Effects of Weathered Soil Parent Materials on Merlot Grapevines Grafted onto 110 Richter and 101-14Mgt Rootstocks

In a trial under semi-controlled conditions, Merlot grapevines on 101-14Mgt and 110 Richter (110R) rootstocks were grown in virgin soils developed in highly weathered parent materials derived mainly from granite and metasediment (shale). Each soil was irrigated at c. -0.075 MPa. The clay fractions of both soils were dominated by kaolinite. Lime and P were supplied, but no K. Bray II soil K levels from both parent materials were similar in the field state, but lower in the shale than in the granite when averaged over the trial period. Petiole K concentrations did not differ between rootstocks on the granite, but on the shale soils were higher in the vines on 101-14Mgt than on 110R. The granite x 101-14Mgt treatment significantly promoted (p ≤ 0.05) greater trunk circumferences, cane mass, leaf areas and overall wine quality than the shale x 110R treatment. Yields from grapevines in the granite x 110R and granite x 101-14Mgt treatments did not differ significantly. However, the granite x 101-14Mgt treatment produced higher yields than the shale x 101-14Mgt and shale x 110R treatments. These differences were attributed to an interaction between the soil and rootstock, with K availability and uptake as contributory factors.

Geogenic cadmium pollution and potential health risks, with emphasis on black shale

Cadmium (Cd) is a non-essential trace element that is toxic to humans. Previous studies of Cd in the environment have primarily focused on pollution resulted from anthropogenic sources, but little is known on naturally occurring sources of Cd. This paper aims to review the geochemical distribution of geogenic Cd and associated environmental risk. The source, accumulation, mobility, transportation, and health risk of Cd are discussed in a geo-environmental perspective, with an emphasis on black shale soils. Cadmium generally occurs in sulfides in black shale, and is easily released when exposed to oxygen and water. Leaching of these rocks tends to elevate Cd concentrations in aquatic systems, and may pose the potential to produce acid rock drainage (ARD) as well. Weathering of Cd-rich rocks also elevates soil Cd concentrations, and influence the geochemical species of Cd. Crops grown in these soils tend to accumulate higher Cd and threaten the food safety. Local inhabitant exposed to high geogenic Cd via food chains may experience Cd-related health risk. High Cd concentrations are observed in urine, and renal damage is also detected in Cd naturally enriched area based on low molecular weight proteins in urine. Overall, the findings in literature have provided with insights for potential health risk of Cd in areas with high Cd geochemical background levels, particular for the black shale exposed areas, more attentions should be paid on the geogenic Cd pollution, and suitable strategies of remediation and geo-environmental management for geogenic Cd pollution need further research.

Effects of Subsetting by Parent Materials on Prediction of Soil Organic Matter Content in a Hilly Area Using Vis-NIR Spectroscopy.

Assessment and monitoring of soil organic matter (SOM) quality are important for understanding SOM dynamics and developing management practices that will enhance and maintain the productivity of agricultural soils. Visible and near-infrared (Vis–NIR) diffuse reflectance spectroscopy (350–2500 nm) has received increasing attention over the recent decades as a promising technique for SOM analysis. While heterogeneity of sample sets is one critical factor that complicates the prediction of soil properties from Vis–NIR spectra, a spectral library representing the local soil diversity needs to be constructed. The study area, covering a surface of 927 km2 and located in Yujiang County of Jiangsu Province, is characterized by a hilly area with different soil parent materials (e.g., red sandstone, shale, Quaternary red clay, and river alluvium). In total, 232 topsoil (0–20 cm) samples were collected for SOM analysis and scanned with a Vis–NIR spectrometer in the laboratory. Reflectance data were related to surface SOM content by means of a partial least square regression (PLSR) method and several data pre-processing techniques, such as first and second derivatives with a smoothing filter. The performance of the PLSR model was tested under different combinations of calibration/validation sets (global and local calibrations stratified according to parent materials). The results showed that the models based on the global calibrations can only make approximate predictions for SOM content (RMSE (root mean squared error) = 4.23–4.69 g kg−1; R2 (coefficient of determination) = 0.80–0.84; RPD (ratio of standard deviation to RMSE) = 2.19–2.44; RPIQ (ratio of performance to inter-quartile distance) = 2.88–3.08). Under the local calibrations, the individual PLSR models for each parent material improved SOM predictions (RMSE = 2.55–3.49 g kg−1; R2 = 0.87–0.93; RPD = 2.67–3.12; RPIQ = 3.15–4.02). Among the four different parent materials, the largest R2 and the smallest RMSE were observed for the shale soils, which had the lowest coefficient of variation (CV) values for clay (18.95%), free iron oxides (15.93%), and pH (1.04%). This demonstrates the importance of a practical subsetting strategy for the continued improvement of SOM prediction with Vis–NIR spectroscopy.

To the problem of classification of ecosystems of south-east Ukraine

This work addresses modern approaches to the classification of ecosystems as a tool for understanding of their diversity and relation to geographical and environmental systemic factors, as well as for solving practical problems of conservation and rational management. A classification of ecosystems of south east Ukraine is given based on the dominant vegetation classification. The basis of classification is the division of ecosystems according to the type of macroecotope (watershed, gully, above flood-plain terrace, floodplain) and edaphotope (developed black soil, washed away black soil on rocky sandstone outcrops, shale, granite, marl, limestone, chalk, sandy and meadow soils). The basis for the division of ecosystems of the same level of each class is based on different features: topical, physionomic, edaphic, dynamic. Classification is based on hierarchical principle. The class of natural ecosystems with dominance of phanerophytes includes ecosystems of coniferous forests and deciduous forest ecosystems of nemoral type, represented mainly by lowland-watershed, gully (ravine) oakeries. The class of natural grass and shrub ecosystems is represented by wetland, grassland and extremely diverse steppe ecosystems. Both classes include ecosystems with different moistening, soil erosion and confinement to edafotopes, developed at the outcrops of different rock types. Class of anthropogenic ecosystems is outlined in general and needs more detailed study. We compiled a lists of formations and subformations of vegetation, belonging to of the lower hierarchy level ecosystems.

Occurrence of shale soils along the Calabar-Itu highway, Southeastern Nigeria and their implication for the subgrade construction.

This study concerned a stretch of 17 km of a 94-km highway alignment in Southeastern Nigeria that has a high incidence of pavement failure arising from subgrade failure. The subgrade of this section of the roadway is composed of Ekenkpon shale, New Netim marl, and Nkporo shale. Under the Unified Soil Classification System, the shales classify as OH (organic clay) and the marl classifies as MH (inorganic silt). Under the American Association of State and Transportation Officials (AASHTO) M 145 soil classification, all these soils classify as A-7-5 soil. Using the AASHTO M 145 group index, none of these soils was considered suitable as subgrade in its native form. Therefore, cement was investigated as a stabilizing agent. Testing demonstrated that 7, 3 and 12 % by weight were the optimum cement contents to reinforce the Ekenkpon shale, New Netim marl, and Nkporo shale, respectively.

Silicon Reduces Cadmium and Arsenic Levels in Field-Grown Crops

This study investigates, under field conditions, whether silicon (Si) addition reduces the accumulation of Cd and As in the edible parts of potato, carrot, onion, and wheat plants. Plants were grown in commercial plantations on alum shale soil in Hedmark County, Norway. Silicon, 500 kg per ha, was added in several forms for comparison: 1) potassium silicate solution, 2) Microsilica, an amorphous SiO2, and 3) Solaritt, a mixture of CaSiO3, Ca3Si2O7, and CaO. The concentrations of Si, Cd, and As were analysed in the edible plant parts and in the total and available soil fractions. Results indicate that Si addition increased the Si content by 12–28 % and reduced the Cd and As contents by 10–25 % and 20–40 %, respectively, in the edible parts of all investigated plants. In the soil, available Si increased up to 10-fold with Si addition while available As and Cd did not change. Potassium silicate and Microsilica had the highest effects due to the high plant availability of their Si content in soil. We conclude that increased plant-available soil Si reduces the As and Cd contents in edible parts of the investigated species and is not due to decreased As and Cd availability in the soil.

Parental material and cultivation determine soil bacterial community structure and fertility.

Microbes are the key components of the soil environment, playing important roles during soil development. Soil parent material provides the foundation elements that comprise the basic nutritional environment for the development of microbial community. After 30 years artificial maturation of cultivation, the soil developments of three different parental materials were evaluated and bacterial community compositions were investigated using the high-throughput sequencing approach. Thirty years of cultivation increased the soil fertility and soil microbial biomass, richness and diversity, greatly changed the soil bacterial communities, the proportion of phylum Actinobacteria decreased significantly, while the relative abundances of the phyla Acidobacteria, Chloroflexi, Gemmatimonadetes, Armatimonadetes and Nitrospira were significantly increased. Soil bacterial communities of parental materials were separated with the cultivated ones, and comparisons of different soil types, granite soil and quaternary red clay soil were similar and different with purple sandy shale soil in both parental materials and cultivated treatments. Bacterial community variations in the three soil types were affected by different factors, and their alteration patterns in the soil development also varied with soil type. Soil properties (except total potassium) had a significant effect on the soil bacterial communities in all three soil types and a close relationship with abundant bacterial phyla. The amounts of nitrogen-fixing bacteria as well as the abundances of the nifH gene in all cultivated soils were higher than those in the parental materials; Burkholderia and Rhizobacte were enriched significantly with long-term cultivation. The results suggested that crop system would not deplete the nutrients of soil parental materials in early stage of soil maturation, instead it increased soil fertility and changed bacterial community, specially enriched the nitrogen-fixing bacteria to accumulate nitrogen during soil development.

Assessment of Selenium Bioavailability in Tea Plantation Soil to Bashan Tea Species (Wanyuan, Southwest China) Using Single Extraction Methods

Se concentration varies for different soil types, whether can be absorbed by plants is not related with the total amount of selenium, it is controlled by the bio-availability Se in soil. This paper is aim to look for the laws of the bio-availability Se in different soils, and find out an accuracy and effective method to extract the bio-available Se from different soil types. Digest the soil and tea leaves samples and used six methods (KH2PO4, NaHCO3, HAC, MgCl2, HCl, EDTA) to extract Se from the different soils, the result was measured by AFS. The mean values of total Se is 8.45μg/g in carbonaceous slates soil, 0.32μg/g and 0.41μg/g in malmstone soil, 0.78μg/g in shale soil. The maximum correlation coefficients (r) between the six extract methods and tea leaves about the extraction ratio of Se in four soils is 0.93188 with KH2PO4, 0.77097 and 0.83589 with NaHCO3, 0.84231 with HAC. So it can be indicate that the total Se contents is carbonaceous slates soil>shale soil>malmstone soil, the best extract method for carbonaceous slates soil, malmstone soil and shale soil are KH2PO4, NaHCO3, and HAC respectively.

Climate dependence of feldspar weathering in shale soils along a latitudinal gradient

Although regolith, the mantle of physically, chemically, and biologically altered material overlying bedrock, covers much of Earth’s continents, the rates and mechanisms of regolith formation are not well quantified. Without this knowledge, predictions of the availability of soil to sustain Earth’s growing population are problematic. To quantify the influence of climate on regolith formation, a transect of study sites has been established on the same lithology – Silurian shale – along a climatic gradient in the northern hemisphere as part of the Susquehanna Shale Hills Critical Zone Observatory, Pennsylvania, USA. The climate gradient is bounded by a cold/wet end member in Wales and a warm/wet end member in Puerto Rico; in between, mean annual temperature (MAT) and mean annual precipitation (MAP) increase to the south through New York, Pennsylvania, Virginia, Tennessee and Alabama. The site in Puerto Rico does not lie on the same shale formation as the Appalachian sites but is similar in composition. Soils and rocks were sampled at geomorphologically similar ridgetop sites to compare and model shale weathering along the transect. Focusing on the low-concentration, non-nutrient element Na, we observe that the extent and depth of Na depletion is greater where mean annual temperature (MAT) and precipitation (MAP) are higher. Na depletion, a proxy for feldspar weathering, is the deepest reaction documented in the augerable soil profiles. This may therefore be the reaction that initiates the transformation of high bulk-density bedrock to regolith of low bulk density. Based on the shale chemistry along the transect, the time-integrated Na release rate (QNa) increases exponentially as a function of MAT and linearly with MAP. NY, the only site with shale-till parent material, is characterized by a QNa that is 18 times faster than PA, an observation which is attributed to the increased surface area of minerals due to grinding of the glacier and kinetically limited weathering in the north. A calculated apparent Arrhenius-type temperature dependence across the transect (excluding NY) for the dissolution of feldspar (Na depletion) is 99±15kJmol−1, a value similar to field-measured values of the activation energy (14–109kJmol−1) or laboratory-measured values of the enthalpy of the albite reaction (79.8kJmol−1). Observations from this transect document that weathering losses of Na from Silurian shale can be understood with models of regolith formation based on chemical and physical factors such that weathering progresses from kinetically limited sites (Wales to AL) to the transport-limited site in Puerto Rico. Significant advances in our ability to predict regolith formation will be made as we apply more quantitative models to such transect studies on shales and other rocks types.