Increase In Organic Matter Content Research Articles

Ecohydrological influences of biocrusts and their pathways in a desert steppe ecosystem

AbstractBiological soil crusts (biocrusts) are a prevalent form of organic cover in drylands across the world, and they play a crucial role in shaping the ecohydrological processes and functioning of dryland ecosystems. However, in desert steppe ecosystems, the ecohydrological influences of biocrusts and their pathways have not yet been thoroughly understood. Here, we examined the influences of three types of biocrusts (cyanobacterial, cyanobacterial‐moss mixed, and moss biocrusts) on soil water retention and infiltration in a typical desert steppe of northwestern China, and we also analysed the possible pathways through which biocrusts affect them. Accordingly, the field capacity (θf, indicating soil water‐holding capacity) and saturated hydraulic conductivity (Ks, indicating soil infiltrability) of each biocrust‐covered soil and bare soil were measured both at 0–5 and 5–10 cm depths, on Arenosols (loamy sand texture) and Calcisols (silty loamy texture), respectively. Our results showed that the presence of biocrusts increased surface soil (0–5 cm) water‐holding capacity while decreased soil infiltrability, creating a remarkable impact on soil water retention and infiltration. As compared to bare soil, the θf of cyanobacterial, cyanobacterial‐moss mixed, and moss biocrusts were increased by 16.5%, 21.4%, and 21.7% on Arenosols and by 9.6%, 18.9%, and 22.8% on Calcisols, while their Ks were reduced by 43.2%, 56.2%, and 38.2% on Arenosols, and by 49.0%, 68.7%, and 36.0% on Calcisols, respectively. The development of biocrusts on sandy textured soil had a more pronounced impact on both soil water retention and infiltration than loamy textured soil. We found that biocrusts mainly changed soil water retention and infiltration by increasing the contents of clay and organic matter. More specifically, the increase in clay content led to a more significant effect compared to the increase in organic matter content on Arenosols, while the opposite influence was observed on Calcisols. Among the three types of biocrusts, the soil infiltrability of the mixed biocrusts was the lowest, perhaps due to the interaction between the accumulation of clay particles by moss and the secretion of extracellular polymeric substances by cyanobacteria. Our study highlights the remarkable ecohydrological impacts of biocrusts on desert steppe ecosystems, and the results imply that it is of great necessary to integrate biocrusts and their influences into our understanding of ecohydrological processes in global drylands.

Sediment variability in intermittently extracted sandbanks in the Belgian part of the North Sea

Introduction: In the Belgian part of the North Sea, sand for beach and foreshore nourishments is extracted from the Hinder Banks, about 40 km offshore. The extraction is not screened for shells and other very coarse material, as is the case for sand extraction for industrial use. Intermittent but intensive sand extraction took place from 2012 to 2019 on the Oosthinder, and since 2019 on the Noordhinder.Methods: To better understand sediment variability during human-induced disturbance of the seabed, both sandbanks have been monitored using multibeam bathymetry and backscatter, and Reineck box cores on board of the Research Vessel Belgica A962. Acoustic and sediment data were preferably jointly collected within a one-week period to substantiate the interrelationships.Result: Very well-sorted medium sands with low backscatter values (−28 to −33 dB) are detected near the top of the sandbank, while (moderately) well-sorted coarser sands and shell fragments with high backscatter values (−20 to −24 dB) are detected in the deeper parts of the sandbank slope. Although natural conditions such as sandwave movement and storms may mask early sediment changes, 7 years of intermittent and intensive sand extraction on the upper parts of a gentle sandbank slope caused a seabed deepening of at least 2 m, a backscatter decrease between 5 and 8 dB, a reduction in carbonate content by 1%–5% and an increase in organic matter content by 1%–2%. Two years after the cessation of the operations, the carbonate content increased and organic matter content decreased by 1%–2%.Discussion: Natural variability of sediments remains dependent on depth and geomorphology in both undisturbed, as well as recently and longer disturbed sandbank systems. However, a spreading of the more homogeneous, very well-sorted medium sands with limited carbonate content from the sandbank crest to the upper parts of the sandbank slope was observed, as sand extraction progressed. Subsequently, possible first signs of a slow return to the original sediment characteristics were detected.

Soil Erosion Satellite-Based Estimation in Cropland for Soil Conservation

Intensive cropland expansion for an increasing population has driven soil degradation worldwide. Modeling how agroecosystems respond to variations in soil attributes, relief and crop management dynamics can guide soil conservation. This research presents a new approach to evaluate soil loss by water erosion in cropland using the RUSLE model and Synthetic Soil Image (spectroscopy technique), which uses time series remotely sensed environmental, agricultural and anthropic variables, in the southeast region of São Paulo State, Brazil. The availability of the open-access satellite images of Tropical Rainfall Measuring Mission (TRMM) and Landsat satellite images provided ten years of rainfall data and 35 years of exposed soil surface. The bare soil surface and agricultural land use were extracted, and the multi-temporal rainfall erosivity was assessed. We predict soil maps’ attributes (texture and organic matter) through innovative soil spectroscopy techniques to assess the soil erodibility and soil loss tolerance. The erosivity, erodibility, and topography obtained by the Earth observations were adopted to estimate soil erosion in four scenarios of sugarcane (Saccharum spp.) residue coverage (0%, 50%, 75%, and 100%) in five years of the sugarcane cycle: the first year of sugarcane harvest and four subsequent harvesting years from 2013 to 2017. Soil loss tolerance means 4.3 Mg ha−1 exceeds the minimum rate in 40% of the region, resulting in a total soil loss of ~6 million Mg yr−1 under total coverage management (7 Mg ha−1). Our findings suggest that sugarcane straw production has not been sufficient to protect the soil loss against water erosion. Thus, straw removal is unfeasible unless alternative conservation practices are adopted, such as minimum soil tillage, contour lines, terracing and other techniques that favor increases in organic matter content and soil flocculating cations. This research also identifies a spatiotemporal erosion-prone area that requests an immediately sustainable land development guide to restore and rehabilitate the vulnerable ecosystem service. The high-resolution spatially distribution method provided can identify soil degradation-prone areas and the cropland expansion frequency. This information may guide farms and the policymakers for a better request of conservation practices according to site-specific management variation.

Preliminary Studies on How to Reduce the Effects of Salinity

Soil salinization is an important factor contributing to the deterioration of soil environment and low crop yield in arable land. In this study, the effects of five fulvic acid applications (0 (CK), 150 (T1), 300 (T2), 450 (T3), and 600 (T4) kg·ha−1) on soil physicochemical properties, humus content of each component, and cotton (Xinluzao No. 82) growth were investigated. It was confirmed that fulvic acid improved soil water-stable macroaggregates, moisture distribution, and desalinization. 0–20 cm soil relative desalinization rate was significantly increased by 2–11.75%. The pH value decreased by 0.09–0.21. The soil organic matter content was significantly increased compared to CK (p < 0.05), with 7.5–26.93% increase in organic matter content in 0–20 cm soil layer. Soil humification was increased to different degrees, with the most significant increase in humic carbon content in T3 treatment (p < 0.05). There was a significant increase in leaf area index (LAI), stem diameter, and plant height of cotton (p < 0.05). Cotton yield increased by 3.64–8.36% compared to CK (p < 0.05). Correlation analysis showed that cotton yield was significantly correlated with the soil textures of saline soils. The best improvement was achieved with 450 kg·ha−1 fulvic acid. The results of this study can provide a theoretical basis for the improvement of saline soils in arid zones to enhance crop growth and yield.

Polygenic soils in the southern central Ecuadorian highlands as the result of long-lasting pedogenesis, geodynamic processes and climate change

In the high altitude (>3000 m asl) grasslands of northern Ecuador, the Páramo ecosystem, soils generally formed on recent volcanic ashes being <10,000 years old in the northern and central part of the cordilleras. With time these soils evolved in to non-allophanic Andisols with hydric properties such as evidenced in profiles from the Cajas massif located in the western central Cordillera. However soils at the Fierro Urcu massif and at the Oña plateau at the eastern Cordillera formed on a non pyroclastic indurated parent material. Compared to non-allophanic Andisols from the Cajas massif, they present similar morphological properties with a dark 50 cm thick carbon-rich (80–120 g kg−1) topsoil with a very low bulk density (<0.65 g cm−3) and high water retention. These top soils appear to have originated from fall-out, derived from close and still active volcanoes of Sangay and/or Tungurahua, both located in a distance of 200–250 km NNE of the Oña Massif, respectively. Geochemical determinations of trace and rare earth elements, however, confirm the lack of volcanic ash contribution in the Saraguro and Oña samples based on Eu/Eu* and Ce/Ce* anomalies relative to the lack of such anomalies in the Cajas samples. The Oña and Saraguro soils appear to be the result of a long-lasting double pedogenic process. The basement of the Saraguro soil is a Ferralsol with gibbsite and kaolinite and the Oña soil is a 5 m thick kaolinitic Ferralsol. The upper part of these profiles are the result of a major climatic change with increasing colder conditions, generating an increase in organic matter content and a very acidic environment leading to the instability of kaolinite and gibbsite, thereby liberating large amounts of free aluminium and iron oxides. The evolution of these very highly evolved Ferralsols into soils with Andic properties is proposed to be the result of rapid tectonic uplift calculated at a rate exceeding 0.6 mm/year in the region leading to a general decrease in temperature limiting carbon mineralization and favouring the formation of organo-metallic complexes. The soils studied here reveal compelling new evidence and information about the uplift of a part of the Ecuadorean Andes.

Strength Properties of Cement-Solidified Dredged Sludge Affected by Curing Temperature

In this study, unconfined compressive strength (qu) tests were conducted to explore the coupling effect of organic matter content (3.7%, 7.7%, 10.7%, and 13.7%) and curing temperature (18 °C, 36 °C, 46 °C) on the development of early and mid-late strength of cement-solidified dredged sludge (cement-stabilized clay, or CSC). The microstructure of the CSC containing organic matter at different curing temperatures was also analyzed. The results show that qu of CSC decreases with the increase in organic matter content (Co). The strength growth rate of CSC in the mid-late stage (≥14 days) is small when Co ≥ 7.7%, and it is difficult to increase this strength growth rate even if the curing temperature is increased up to 46 °C. There is a cement incorporation ratio threshold of 15% for qu of CSC containing organic matter (Co = 7.7%), which is not affected by curing temperature; increasing the cement incorporation ratio (to 20%) cannot increase qu significantly. The CSC with high curing temperature has more hydration products and higher structural compactness, and it can obtain higher qu in the early and mid-late stages. A high curing temperature can increase the early strength growth rate and shorten the curing age for CSC containing organic matter.

Impact of Short-Term Cultivation on Some Selected Properties of Sandy Soil in an Arid Environment

Soil management is recognized to have an impact on soil quality attributes. Depending on the management approach, this impact can either degrade or improve soil quality. There is a severe shortage of information on the impacts of cultivation on sandy soil properties in arid desert regions. Therefore, the objective of this study was to investigate the short-term cultivation effects (5 years) on the properties’ changes of coarse-textured soil in an arid desert region in western Assiut Governorate, Egypt. The current study was conducted on soils sampled at four depth intervals, namely 0–10, 10–20, 20–30, and 30–40 cm, from both cultivated and uncultivated soils, using a systematic sampling grid (10 × 10 m), to investigate the potential impacts of the cultivation process on six soil attributes. Each land use was represented by an area of 0.5 ha (50 × 100 m). A total of 160 composite soil samples (at all depths) were collected from both soils and analyzed for their physical and chemical properties, employing standard laboratory procedures. The data were statistically and geostatistically analyzed to compare the results and map the spatial distributions of the selected soil properties. The results revealed that cultivation had a considerable positive impact on most of the properties of cultivated soil compared to those of uncultivated soil (virgin land). The findings also showed that the available phosphorus levels in cultivated soil were higher than in virgin soil by 16, 9, 8.5, and 6 folds, with increases in organic matter content of 16.8, 12.4, 11.9, and 7.9 times at depths of 0–10, 10–20, 20–30, and 30–40 cm, respectively. Furthermore, compared to virgin soil, cultivated soil exhibited a salinity reduction of −8.9%, −56.4%, −66.3%, and −71.8%, at depths of 0–10, 10–20, 20–30, and 30–40 cm, respectively. Moreover, some other properties of the cultivated soil improved, particularly in the surface soil layers, such as pH reduction, CaCO3 decline, and CEC increase, while the soil texture grade did not change. Therefore, continuous monitoring of the effects of diverse soil management strategies in the short term assists in the understanding of the ongoing changes in soil physical and chemical characteristics, which is critical for maintaining satisfactory soil quality and sustainable soil productivity in arid lands.

Lipid Biomarker and Stable Isotopic Profiles through Late Carboniferous–Early Triassic of the Deepest Well MS-1 in the Junggar Basin, Northwest China

The Carboniferous–Triassic period was an important stage of global sea–land transformation, with coal formation in the Carboniferous, biological extinction at the end of the Permian, and global drought in the Triassic. The MS-1 well in the Mosuowan High of the Junggar Basin is the deepest well drilled in Northwestern China. In this paper, we investigate the sedimentary environment and climate evolution of the Mosuowan area in the central Junggar Basin during the Late Carboniferous–Early Permian by the petrothermal, lipid biomarker, and isotopic composition of mud shale core samples, and explore the tectonic–climatic events and Central Asian orogenic belt evolution driving the sedimentary environment. The study shows that the organic matter from the Upper Carboniferous to the Lower Permian is at a mature stage, but biomarkers maintained the primary information although the organic matter was subjected to thermal evolution. In the late Carboniferous period (Tamugan Formation), the study area was a closed remnant sea with a relatively humid climate, triggering lush terrestrial vegetation and high organic carbon content in the sediments, which had the potential to evolve into natural gas. During the Xiazijie Formation of the Middle Permian, tectonic activity shifted to the subsidence period, and the salinity of the water decreased after a large input of fresh water. The lake basin area expanded, and the content of aquatic organisms continued to increase. As the Lower Permian stratigraphy is missing, this sea–land transition seems to jump. The low and upper Urho Formations of the Middle–Upper Permian are a deltaic foreland deposit, and geochemical indicators show an overall lake retreat process with a continuous increase in organic matter content of terrestrial origin. The lithologic assemblage of the Triassic Baikouquan Formation is braided river deltaic sedimentation with migration of deposition centers of the lake basin. In conclusion, the Late Carboniferous–Early Permian period was influenced by global changes, Paleo-Asian Ocean subduction, and continental splicing, which resulted in a continuous increase in terrestrial organic matter, water desalination, and oxidation-rich sediments in the Mosuowan region, but the P–T biological mass extinction event was not recorded.

Paleolimnological records for tracking dam-induced changes in the composition and supply of sediment to middle Yangtze floodplain lakes

A global boom in dam construction has reduced sediment loading of large rivers, as well as their connected floodplains. In order to explore potential effects of hydrological regulation on floodplain ecosystems, this study presents concentrations of inorganic elements, organic matter content and grain size spectra in 210Pb-dated sediment cores of five lakes in the middle Yangtze River floodplain. These lakes had free hydrological connectivity with the Yangtze River before the operation of local sluice gates, and hence K-rich but Al-poor particulates from the upper Yangtze reaches can be transported into lakes during periods of high river discharge. After hydrological regulation, sedimentary K/Al ratios registered substantial decreases in the study lakes, probably due to the declining supply of fine-grained and K-enriched riverine particulates from the Yangtze River. In East Dongting Lake, a hydrologically open lake proximal to the Three Gorges Dam (TGD), the sharp decrease in K/Al ratio after 2003 mainly responded to declining sediment supply from the Yangtze River after the TGD operation. In addition, prolonged water retention time probably promoted aquatic production and greater deposition of organic matter, as indicated by recent increases in organic matter content in the upper strata of the dammed lakes. Taken together, sedimentary K/Al ratios provide essential information on effects of past hydrological changes on sediment supply and aquatic productivity over multi-decadal timescales in these floodplain lakes with scarce monitoring data. The impacts of dam construction during recent decades on sediment composition in middle Yangtze floodplain lakes might be widespread in other similar floodplains worldwide. Thus sedimentary records can be utilized to inform and direct floodplain management.

Leaching of saflufenacil in soils with different organic matter contents

Saflufenacil is a herbicide recommended for use in the main agricultural crops in Brazil to control eudicotyledonous weeds. However, the application of saflufenacil has been carried out without previous knowledge of this herbicide interactions with soil colloids, which may increase environmental contamination risks. In this study, the leaching of saflufenacil in soil samples was estimated with different organic matter contents. Therefore, PVC columns were filled with samples of Xanthic Ferralsol (XF) and Ferralsol (F), with different physical and chemical attributes. Twelve hours after herbicide (70 g i.a. ha-1) application, the PVC columns were subjected to a rainfall of 60 mm. For the evaluation of saflufenacil leaching, the columns were sectioned in ten parts with 5-cm each. Saflufenacil leached up to 50 and 40 cm deep in the samples, with the lowest contents of organic matter of XF and F, respectively. The increase in organic matter content of Ferralsol and Xanthic Ferralsol samples reduced saflufenacil leaching and the symptoms of intoxication in the indicator species. There was an inverse relation between the content of organic matter and the leaching of the herbicide in both soils studied. It was observed that the application of saflufenacil in soils with low organic matter contents may represent a significant environmental contamination risk of soils and watercourses.

KAJIAN BEBERAPA SIFAT FISIKA TANAH YANG DITANAMI KELAPA SAWIT PADA UMUR DAN KELERENGAN YANG BERBEDA (Studi Kasus Perkebunan Sawit Kelurahan Simpang Tuan, Kecamatan Mendahara Ulu,Tanjung Jabung Timur)

Land clearing for oil palm plantations using heavy equipment will affect the physical properties of the soil, namely increasing soil compaction and decreasing soil porosity and soil moisture content. However, along with the growth of plantation crops such as oil palm, it is suspected that it can restore the physical properties of the soil. The aim of the study was to examine the differences in the physical characteristics of the soil at various ages of oil palm and the slope. The study was conducted in one of the oil palm plantations, Simpang Tuan Village, Mendahara Ulu District, Tanjung Jabung Timur Regency from March to May 2021. The study was carried out using the survey method, selecting representative areas using the Purposive Random Sampling method on oil palm plantation areas with various ages (newly planted, 5 years old, and 12 years old) and various marbles (0-3%, 3-8%, and 8-15%) with 3 replications. Parameters observed were soil texture, soil organic matter content, bulk density, water content, and soil permeability. The results showed that the older the age of oil palm plantations, the increase in organic matter content, total pore space, water content and soil permeability and a decrease in volume weight. The steeper the slope, the greater the weight of the soil volume and a decrease in the organic matter content, total pore space, water content and soil permeability.

Evaluation on the anisotropic brittleness index of shale rock using geophysical logging

The brittleness index plays a significant role in the hydraulic fracturing design and wellbore stability analysis of shale reservoirs. Various brittleness indices have been proposed to characterize the brittleness of shale rocks, but almost all of them ignored the anisotropy of the brittleness index. Therefore, uniaxial compression testing integrated with geophysical logging was used to provide insights into the anisotropy of the brittleness index for Longmaxi shale, the presented method was utilized to assess brittleness index of Longmaxi shale formation for the interval of 3155–3175 m in CW-1 well. The results indicated that the brittleness index of Longmaxi shale showed a distinct anisotropy, and it achieved the minimum value at β = 45°-60°. As the bedding angle increased, the observed brittleness index (BI2_β) decreased firstly and increased then, it achieved the lowest value at β = 40°–60°, and it is consistent with the uniaxial compression testing results. Compared to the isotropic brittleness index (β = 0°), the deviation of the anisotropic brittleness index ranged from 10% to 66.7%, in other words, the anisotropy of brittleness index cannot be ignored for Longmaxi shale. Organic matter content is one of the main intrinsic causes of shale anisotropy, and the anisotropy degree of the brittleness index generally increases with the increase in organic matter content. The present work is valuable for the assessment of anisotropic brittleness for hydraulic fracturing design and wellbore stability analysis.

Soil organic carbon stock is improved by cover crops in a tropical sandy soil

AbstractSoil organic matter plays an important role in soil quality. In sandy soils of tropical regions, high biological activity in the soil accelerates mineralization and limits increases in organic matter content. The objective of this study was to evaluate the total organic C stock and the chemical and physical fractions of organic C in a sandy soil in Presidente Bernardes, São Paulo, Brazil, as a function of cover cropping with different combinations of grasses and legumes between 2015 and 2020. The treatments comprised fallow (control), cultivation of a single grass or intercropping of two grasses, one grass and one legume, or a mixture of two grasses and one legume during the offseason (April–September). Intercropping two grasses increased total dry matter production (shoot and root) by 138% and decreased the C/N ratio by 19% compared with the fallow and legume systems. The organic C stock in the soil was 46% higher in the mixed cover crop system (36.5 Mg ha−1) than in the fallow system (25 Mg ha−1). Humic acid (0.78–0.82 g kg−1) and humin (1.68–1.99 g kg−1) were lower in the systems with low dry matter production (fallow and grass + legume). Mineral‐associated C content was 114% higher in the mixed cover crop system than in the fallow system. These results show that cover crops can increase C content in all fractions of organic matter in tropical sandy soil, even in a short period of time (5 yr), and that a mix of cover crops is the best option.

WHAT IS THE EFFECT OF COMPOST ON THE CHARACTERISTICS OF A SANDY SOIL AFTER TWO SEASONS OF OKRA (ABELMOSCHUS ESCULENTUS) CULTIVATION IN THE NIAYES AREA OF SENEGAL?

Soil is both a support and a nutrient source for the development of living organisms. Composts based on faecal sludge and vegetable wastes were tested on okra to see the proportion of organic matter and nutrients in the soil after two seasons. Thus the control, non-composted faecal sludge and chemical fertiliser were compared with the other treatments T0, T1 and T2. Physicochemical parameters such as pH, electrical conductivity, organic matter, nutrients Carbon, Nitrogen, Potassium, Phosphorus and grain size were analysed. The results showed an increase in organic matter content from the beginning (As = 0.52%) with 1.72%, 1.9% and 1.4% for the soil samples that were amended with T0, T1 and T2 respectively. Thus the pH values are neutral for treatments T0, T1 and T2. The electrical conductivities are between 33-47µs/cm. Mineral elements such as A (0.08-0.1%), P (21.7-29.6%), K (0.02-0.03%), are satisfactory for T0, T1 and T2. The C/N ratio is between 9.5-10.4 and below 12.

Interplay between eutrophication and climate warming on bacterial communities in coastal sediments differs depending on water depth and oxygen history

Coastal aquatic systems suffer from nutrient enrichment, which results in accelerated eutrophication effects due to increased microbial metabolic rates. Climate change related prolonged warming will likely accelerate existing eutrophication effects, including low oxygen concentrations. However, how the interplay between these environmental changes will alter coastal ecosystems is poorly understood. In this study, we compared 16S rRNA gene amplicon based bacterial communities in coastal sediments of a Baltic Sea basin in November 2013 and 2017 at three sites along a water depth gradient with varying bottom water oxygen histories. The shallow site showed changes of only 1.1% in relative abundance of bacterial populations in 2017 compared to 2013, while the deep oxygen-deficient site showed up to 11% changes in relative abundance including an increase of sulfate-reducing bacteria along with a 36% increase in organic matter content. The data suggested that bacterial communities in shallow sediments were more resilient to seasonal oxygen decline, while bacterial communities in sediments subjected to long-term hypoxia seemed to be sensitive to oxygen changes and were likely to be under hypoxic/anoxic conditions in the future. Our data demonstrate that future climate changes will likely fuel eutrophication related spread of low oxygen zones.

Effect of organic matter content on Atterberg limits and undrained shear strength of river sediment

The Atterberg limits and the undrained shear strength are crucial soil properties in the preloading design of reclamation foundation projects using dredged river sediment. These properties can be significantly affected by the presence of organic matter in the sediment. This study investigates the physical properties and undrained shear strength of river sediment, based on data from a series of fall cone tests performed on river sediment with different organic matter contents, and undrained shear strength data for reconstituted clay collected from the literature. It was found that the liquid limit, plastic limit, and plasticity index increase with an increase in organic matter content. The effect of organic matter on the undrained shear strength of remolded soil at a given water content can be attributed to the effect of organic matter on the liquid and plastic limits. The undrained shear strength is a function of the liquid and plastic limits; it can be normalized by the liquidity index, irrespective of the organic matter content. Highlights Investigating role of organic matter in the Atterberg limits Investigating role of organic matter in shear strength Understanding key factors of controlling shear strength Establishing organic matter–liquidity index–shear strength interrelations

Variation of soil properties with sampling depth in two different light-textured soils after repeated applications of urban sewage sludge

Semi-arid agricultural soils have increasingly been subjected to urban sewage sludge (USS) applications due to accelerated soil depletion and shortages in manure supply. Research studies addressing USS reuse have mostly been conducted in cropping systems and focused on changes in topsoil properties of a given texture. Therefore, sludge-soil interactions could be largely influenced by the presence of plants, soil particle composition and depth. In this field study, two agricultural soils (sandy, S and sandy loam, SL) received simultaneously four annual USS applications of 40, 80, and 120 t ha−1 year−1 in absence of vegetation. Outcomes showed the increase of carbon and macronutrients in both soils proportionally to USS dose especially in the topsoil profile (0–20 cm). Subsoil (20–40 cm) was similarly influenced by sludge rates, showing comparable variations of fertility parameters though at significant lower levels. The depth-dependent improvement of soil fertility in both layers enhanced the microbiological properties accordingly, with significant variations in soil SL characterized by a higher clay content than soil S. Besides, positive correlations between increases in sludge dose, salinity, trace metals, and enzyme activities in both soils indicate that excessive sludge doses did not cause soil degradation or biotoxic effects under the described experimental conditions. In particular and despite high geoaccumulation indices of Ni in both soils and profiles, the global concentrations of Cu, Ni, Pb, and Zn were still below threshold levels for contaminated soils. In addition, the maintenance of pH values within neutral range and the increase of organic matter content with respect to control would have further reduced metal availability in amended soils. Therefore, we could closely investigate the effects of texture and depth on the intrinsic resilience of each soil to cope with repetitive USS applications.

From glacial times to late Holocene: Benthic foraminiferal assemblages from cold water coral habitats off northwest Scotland

Benthic foraminiferal assemblage data have been derived from a marine sediment core collected in a cold-water coral (CWC) site off northwest Scotland (near the Wyville Thomson Ridge - WTR). The record covers the last glacial period to the late Holocene. Our reconstructions enable to better constrain the paleoenvironmental changes that took place in the study area since the last glacial time and define the environmental conditions that allowed the onset, formation and decline of CWCs in the area. The sedimentary record was characterized by three distinct foraminiferal assemblages, dominant during the pre-coral time interval (i and ii) and the coral period (iii): (i) the “Glacial” assemblage (>13 cal ka BP) was characterized by the dominance of Cibicides refulgens and Discanomalina coronata. Low foraminiferal densities and diversities indicated unfavorable ecological conditions (i.e., low temperature and food availability, coarse substrate) that were most likely related to the extended British Ice Sheet; (ii) the “Deglacial-Early Holocene” assemblage (~13–9 cal ka BP) was characterized by the cassidulinids-Lobatula lobatula association, indicating a progressive increase of organic matter content and influx of warm and saline North Atlantic surface waters. We hypothesize that these were the main environmental factors that thereafter allowed the settlement of CWCs in the WTR area around 9 cal ka BP; (iii) the “Holocene” (<9 cal ka BP) assemblage was characterized by the cohabitation of diverse epifaunal species (e.g., Rosalina globularis) present when CWCs were highly abundant, and infaunal species (e.g., Trifarina angulosa) when corals were less frequent. The periods recording high presence of T. angulosa after 9 ka cal BP were interpreted as indicating a higher contribution of Eastern North Atlantic Waters during periods of retracted Subpolar Gyre (SPG), affecting probably the efficiency of food export to the seafloor.

Microscale Evaluation of Tight Oil Mobility: Insights from Pore Network Simulation

Pore network modeling based on digital rock is employed to evaluate the mobility of shale oil in Qingshankou Formation, Songliao Basin, China. Computerized tomography technology is adopted in this work to reconstruct the digital rock of shale core. The pore network model is generated based on the computerized tomography data. We simulate the dynamics of fluid flow in a pore network model to evaluate the mobility of fluid in shale formation. The results show that the relative permeability of oil phase increases slowly in the initial stage of the displacement process, which is mainly caused by the poor continuity of the oil phase. In the later stages, with the increase in the oil phase continuity, the range of relative permeability increases. With the increase of organic matter content, the permeability of the water phase remains unchanged at low water saturation, but gradually increases at high water saturation. At the same time, it can be seen that, with the increase in organic matter content, the isosmotic point of the oil–water phase permeability shifts to the left, indicating that the wettability to water phase gradually weakens.

Effects of Different Organic Fertilizers on Improving Soil from Newly Reclaimed Land to Crop Soil

The rapid development of cities in the recent 10 years caused a reduction in the cultivated land area, which only accounts for 14% of the total land area in China. Land development and reclamation have been regarded as an effective way to compensate farmland occupation. However, most of the newly reclaimed land has poor soil fertility and suitability; in some cases, the production capacity is only 10–30% of the occupied farmland. In order to ameliorate the soil quality of the newly reclaimed land, this study evaluated the effects of commercial organic fertilizer (0.75, 1.50, and 2.25 kg/m2), mushroom residue (1.50, 2.25, and 3.00 kg/m2), biogas slurry (150, 225, and 300 kg/m2), vegetable cake (0.30 and 0.60 kg/m2), and chemical compound fertilizer (37.50 g/m2) on the pH, moisture content and organic matter content (OMC), available phosphate, total nitrogen, alkaline hydrolysis nitrogen, microbial biomass carbon and nitrogen, and number of total bacteria and phosphate-solubilizing bacteria, as well as the growth of maize seedlings. The results from this study indicate that the soil quality (OMC is an indicator) was ameliorated by chemical and organic fertilizers, in particular commercial organic fertilizers, which caused a 9.35–16.35% increase in moisture content, a 11.56–18.72% increase in pH, a 1.73–2.15 fold increase in OMC, a 338.44–491.41% increase in available P, a 36.80–48.14% increase in total N, a 95.32–128.34% increase in alkaline hydrolysis N, a 92.57–178.38% increase in total bacterial numbers, and a 7.57–20.87 fold increase in microbial biomass carbon compared with the control. The pot experiment further indicated that soil amended with commercial organic fertilizers caused a 20.35–30.55% increase in the height and a 12.50–16.67% increase in the total dry weight of maize seedlings. In addition, representative strains with the ability to dissolve phosphorus and fix nitrogen were successfully isolated using the culture method, and were then identified based on colony morphological observation and 16S rDNA sequence analysis, which help us to not only understand why organic fertilizer has great effect on soil improvement, but also provides beneficial microbial resources for further study.