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Author(s):  
Camila P. Cagna ◽  
Osvaldo Guedes Filho ◽  
Alexandre R. C. Silva ◽  
Cássio A. Tormena

ABSTRACT The objective of this study was to automate the acquisition of water travel time, as well as the computation of hydraulic conductivity of saturated soil by the falling head method, using water sensors and the Arduino platform. To automate the measurement of travel time, the Arduino Uno board was used, and two water sensors were installed at the initial (h0) and final (h1) heights of the water inside the core. When the water flows across the soil and the water level passes the bottom part of the initial sensor (h0), the time recording starts; it ends when the water is absent from the final height of the second sensor (h1). The equation for calculating the hydraulic conductivity was inserted into the algorithm so the calculation was automatic. Undisturbed soil samples were taken in a long-term no-tillage area. There were no significant differences for the time and hydraulic conductivity means between the permeameters. The coefficient of the residual mass index showed an overestimation of the time variable; thus, the automated permeameter improves the precision of time recording and saturated hydraulic conductivity estimated by the falling head method.


Author(s):  
Fangting Wang ◽  
Ke Bao ◽  
Changsheng Huang ◽  
Xinwen Zhao ◽  
Wenjing Han ◽  
...  

Cadmium is a toxic element with a half-life of several decades, which can accumulate in the human body by entering the food chain and seriously harm health. The cadmium adsorption and desorption processes in the soil directly affect the migration, transformation, bioavailability, and ecotoxicity of this element in soil-plant systems. Coastal zones are located in the transitional zone between land and sea, and large amounts of terrigenous material input have important environmental effects on this ecosystem. The pH, hydrodynamic conditions, soil organic matter (SOM), and other factors defining the sea-land interaction within the sedimentary environment are significantly different from those defining land facies. In order to study the key factors affecting cadmium adsorption in soils at the sea-land interface in the Nansha area of the Pearl River Delta, a test was conducted on a column of undisturbed soil. The results showed that the adsorption constant KF and the Cd2+ adsorption capacity of marine soils were higher than those of terrestrial soils. However, the saturation adsorption of cadmium in terrestrial sediments was higher than in marine sediments. Soil pH was an important factor affecting cadmium adsorption capacity in both terrestrial and ma-rine sediments. Neutral and alkaline topsoil conditions inhibited the vertical migration of cadmium, while the acidic environment favored it. The higher the clay and SOM were, the stronger the Cd2+ adsorption capacity of the soil was. These findings suggest that the distribution of cadmium in marine and continental sedimentary soils is not only related to adsorption, but also to the physical and chemical processes occurring in different sedimentary environments.


Author(s):  
Gülay Karahan

Sorptivity (S) is the fundamental variable controlling the early infiltration process. Besides soil properties, soil initial water content (θi) and/or matric pressure (hi) are key factors determining extent of S. Assessment of interrelationship among S, hi and soil properties can provide a considerable insight into understanding the behaviour of dry soils to rainfall or irrigation water. This study was conducted to evaluate relationship between S and some selected soil parametric and morphometric properties within a range of hi. Sixteen undisturbed soil samples (5 cm id, 5 cm length) were taken from the topsoil (0-15 cm) of a paddy soil with clay texture. Sorptivity was measured with a mini-disc infiltrometer (MDI) on the samples equilibrated at h, ranging from -20 to -1500 kPa. A parameter (η), representing the relationship between S and hi, was introduced. Correlation analysis was conducted between η and selected soil morphometric and parametric properties. Soil structure and clay content appeared the most important soil attributes influencing S-hi relation between -200 and -1500 kPa. The results provided a fundamental understanding on S-hi-soil properties interrelations in a clay soil. The methodology developed in this study can be used to evaluate S-hi relationship across different soils and scales.


Author(s):  
Yijie Shi ◽  
Meiyan Wang ◽  
Tongyan Yao ◽  
Lingying Xu ◽  
Xuezheng Shi

Objective of investigation: Land use conversion strongly alters soil structure and substantially affects soil organic carbon (SOC) sequestration. Changing from an anaerobic paddy field (PF) to a dry land easily causes SOC loss due to stimulation of C decomposition. However, no evidence of SOC loss from PF to intensive vegetable cultivation has been certainly presented. Experimental material: This study was conducted on the long-term cultivated open-field vegetable (OFV) and greenhouse vegetable (GHV) planting area converted from old PF in China. Undisturbed soil cores, natural structured soil, and disturbed soil from top soil layers were using for further analyses. Methods of investigation: To comprehensively investigate SOC and soil structure change in the land use conversion of PF to OFV and PF to GHV, we used 13C-CPMAS NMR spectroscopy to classify the SOC fractions. The soil macropores (> 50 μm) was valued by X-ray computed tomography, and soil aggregates distribution was determined by wet sieving method. Data collection: Data were obtained from the above-mentioned measurements and statistically analyzed in R. Results: The result showed that the SOC stock increased 1-fold from PF to GHV. SOC stability increased with recalcitrant C (aromatic-C and carbonyl-C) raised by 21 %–27 % in GHV bulk soil. Both macropores and macroaggregates (> 250 μm) increased in GHV, accompanied by an accumulation of recalcitrant C in large macroaggregates. Conclusions: we confirmed the expanded GHV cultivation sequestered more belowground SOC than PF, associated with the amplified physical protection by enhancing soil aggregation and by redistributing of soil macropores.


Author(s):  
А.С. Ильинцев ◽  
Е.Н. Наквасина

Колейность, образующаяся при проходе лесозаготовительной техники во время разработки лесосек при рубке леса, является одним из негативных экологических последствий, связанных с нарушениями почвенно-растительного покрова вырубок, определяющим дальнейшую их реновацию. Негативное влияние от формирования колейности зависит от числа проходов техники и связано с почвенно-климатическими условиями. На опытно-производственном участке ООО «Двинлеспром», территориально расположенном в междуречье С. Двины и Пинеги (Архангельская область, северотаежный лесной район европейской части РФ), изучено влияние разного числа проходов (4, 8, 10) груженого форвадера Ponsse Buffalo King по волоку, не покрытому порубочными остатками. Исходный участок леса представлен ельником черничным V класса бонитета, произрастающим на подзолистой почве на двучленных отложениях, широко распространенных в регионе. На постоянных учетных площадках (20 x 5 м), заложенных в 3 повторениях, провели детальное изучение строения колей, в дне каждой колеи вскрыли почвогрунт и сделали описание горизонтов/слоев почвы, взяли ненарушенные образцы почвы с глубины 0–10 и 10–20 см для определения влажности и плотности сложения. Установлено, что число проходов более определяет глубину, чем ширину колей. Выявлено 6 типов нарушений почвенного покрова по строению почво-грунта на дне колеи, связанных с перемешиванием, сдвиганием и выносом на дневную поверхность оглеенных почвообразующих пород. Показана представленность типов строения дна колеи в зависимости от числа проездов груженого форвардера, а также различия в плотности сложения и влажности почво-грунта. Плотность сложения в толще 0– 20 см при увеличении числа проходов техники закономерно увеличивается до значений, соответствующих почвообразующим породам. При этом доля влаги в толще 0–10 см при увеличении числа проходов повышается, а в толще 10–20 см снижается. Заметные изменения изученных показателей достигаются при восьмикратном проезде груженого форвардера, что позволяет считать это число проездом максимально допустимым на подзолистых почвах на двучленных отложениях в северотаежном лесном районе. The ruts formed after the passage of logging machinery during logging operations are one of the negative environmental consequences associated with disturbances of the soil and vegetation cover of deforestation, which determines their further renovation. The negative impact of the formation of ruts depends on the number of passes of machinery and is associated with soil and climatic conditions. We studied the effect of different number of passes (4, 8, 10) of a loaded Ponsse Buffalo King forvader on a skid trail that is not covered by felling residues. The experimental logging site of LLC Dvinlesprom is located in the watershed between of the Northern Dvina and Pinega (Arkhangelsk region, North Taiga forest region of the European part of the Russian Federation). The original site is represented by a blueberry spruce forest of the V class of bonity, which grows on podzolic soil on binomial deposits and is widely distributed in the region. We laid the permanent accounting pads (20 x 5 m) in 3 repetitions. We conducted a detailed study of the structure of the ruts, at the bottom of each rut, we opened the soil and made a description of the horizons/layers of the soil, took undisturbed soil samples from a depth of 0–10 and 10–20 cm to determine the soil bulk density and moisture content. It was found that the number of passes determines the depth more than the width of the ruts. We identified 6 types of disturbances of the soil cover on the structure of the soil at the bottom of the ruts, associated with mixing, shifting and removal of the gleying soil-forming parent soil to the day surface. We have given the types of the structure of the bottom of the ruts depending on the number of passes of the loaded forwarder, as well as the differences in the soil bulk density and moisture content. The soil bulk density in the thickness of 0–20 cm with an increase in the number of passes of the forwarder naturally increases to the values corresponding to the soil-forming parent soil. At the same time, the proportion of moisture in the thickness of 0–10 cm increases with an increase in the number of passes, and in the thickness of 10–20 cm decreases. Noticeable changes in the studied indicators are achieved with an eight-fold passage of a loaded forwarder, which allows us to consider this number as the maximum permissible passage on podzolic soils on binomial deposits in the north taiga forest area.


2021 ◽  
Author(s):  
Ulla Rosskopf ◽  
Daniel UTEAU ◽  
Stephan PETH

Abstract PurposeSoil structure evolving from physical and biological processes is closely related to soil mechanical characteristics and texture. A soil plot experiment in Bad Lauchstädt, Germany, allowed us to study the influence of substrate and genotype on the initial development of mechanical traits, differences between depths, and changes over the course of two years. MethodsPlots were homogeneously filled with a loam and a sand and planted with two maize (Zea mays L.) genotypes (wild type (WT) and rth3 mutant) with contrasting root hair attributes. Undisturbed soil cores were taken in 2019 and 2020 at 14 and 34 cm depth. Confined uniaxial compression tests were performed to determine pre-compression stress (σpc), compressibility (Cc, Cs) and elasticity index (EI). Mechanical energy was calculated based on penetration resistance tests with a penetrometer needle resembling root geometries. Resultsσpc, Cc and Cs were significantly higher in loam as compared to sand, whereas the factor genotype proved to be negligible. Over time, σpc increased and Cc decreased in loam from 2019 to 2020 and Cs declined in both substrates. Higher mechanical energies were observed in loam and partially in WT. Required energy was higher at 14 cm than at 34 cm depth and decreased from 2019 to 2020 in sand. Airdry sand samples required four times as much energy than those at -50 kPa.ConclusionFor the development of the mechanical traits examined texture proved to be the dominating factor and changes in soil stability could be observed within a short period of time.


Author(s):  
Agus Tugas Sudjianto ◽  
Aji Suraji ◽  
Sugeng Hadi Susilo

Expansive clay is one of the problems in construction work. The soil has the characteristics of being easy to expand when exposed to water, causing a decrease in the strength value of the soil. The can be overcome by stabilizing the soil. The soil is formed from weathering and contains the mineral montmorillonite. The soil is very sensitive to moisture content, has a high shrinkage rate, thus interfering in construction work. Therefore, additional materials are needed to overcome the problem, one of which is soil stabilization. The study aimed to stabilize the expansive clay soil. This is done by analyzing the physical and mechanical properties of expansive clay with a shell ash mixture. Expansive clay is taken directly (undisturbed) or disturbed. Undisturbed soil is taken using a tube, so that the soil is not disturbed by outside air, while disturbed soil is taken using a shovel and then put into a sack container. Expansive clay stabilization method lies in adding the percentage of shell ash mixture (5 %, 10 %, 15 %, and 20 %). The soil, the initial moisture content (γd) of which has been determined, is mixed, then molded into a cylindrical shape. The mold was stored in a desiccator, then watered with 5 % water every day until the soil became saturated. Then, using a Proctor test, chemical tests (soil chemical test, soil mineral test), physical tests (soil moisture, Atterberg limit), and mechanical tests (unconfined compression test, compaction test, swelling test) were carried out. The results showed that the addition of an oyster shell ash stabilizing agent to expansive clay affected the physical and mechanical properties of the soil. The addition of shell ash can reduce soil moisture with various plasticity indexes. While the soil stress value decreased, the swelling of the soil increased significantly above the original soil.


2021 ◽  
Vol 4 (3) ◽  
Author(s):  
A. A. Danilova ◽  
A. A. Petrov

The aim of the study. The Azotobacter genus is a well-known bioassay for testing the soil environment quality. A large number of these bacteria is considered as evidence of the ecological well-being of a soil. However, a high number of these microorganisms was found in disturbed ecosystems, which means there is a problem of how to interpret the results of the biotest. Therefore the aim of the study was to clarify the causes of this problem and suggest a possible way to solve it. Location and objects of the study. The study was conducted in West Siberia (Russia) in the Priobskoe plateau (54°53'13.5"N, 82°59'36.7E"). Leached сhernozem with different content of organic matter (mortmass) was studied under the following treatments: 1) permanent fallow, 2) wheat cultivation, annual removal of straw from the field + summer fallow, 3) wheat + left straw + summer fallow, 4) wheat +left straw + green manure fallow, 5) grassland. The content of N-NO3, respectively, was equal to 50, 10, 15, 5, 0 mg/kg. Another object was a site at the mining and processing plant "Denisovsky" in South Yakutia (Russia) (56°46'20.23"N, 124°51'06.95"E). Abandoned for a long time (30 years) after coal mining spoils were studied in two variants: without plants and with well-developed vegetation cover. Total SOC content was 1.8 and 5.7%, N – 0.3 and 0.4 %, respectively. Methodology. The direct sowing of single soil aggregates onto the N-free medium containing glucose as C-source was used to cultivate Azotobacter. Glucose (10 mg/g soil) was added to the soil to activate Azotobacter growth. A live culture of bacteria was introduced into the soil at a dose of 1 ml/g to check the viability of Azotobacter in experimental soils. Main results. The status of the microbial community in situ was observed on microbial landscapes obtained by exposing slides in the undisturbed soil for 30 days. The overgrowth of soil lumps in the specified range of options was 0–80–40–0–0% and after glucose addition – 100–80–80–0%. The activation of Azotobacter growth after glucose addition was inversely proportional to the C: N ratio (between the mortmass and the mineral nitrogen). Live Azotobacter culture under grassland developed 2.5 times slower in comparison with the fallow. Similar patterns were found in the study of the soils developed on the coal mining spoils. Activation of Azotobacter growth by glucose (response to stress) was more pronounced in soils with apparently less favorable environment for bacteria. Conclusion. The reason behind misleading interpretation of Azotobacter biotest results was that the original purpose of the test was to assess fertility of arable soils. This role of the indicator bacterium was previously underestimated. It is known that the arable soil belongs to the category of disturbed ones, and the abundance of Azotobacter may indicate instability in the microbial community of the soil. To expand the capabilities of the biotest, the authors propose to supplement the test with a procedure for evaluating the Azotobacter growth response to experimental stress, e.g. C-substrate addition.


2021 ◽  
Author(s):  
Sylvie Noelle DJUKEM FENGUIA ◽  
David Guimolaire Nkouathio

Abstract Flooding occurs when water is in excess and can no longer be evacuated normally. The nature of the soil has been identified as one of the major causes of flooding, hence this study aimed is to show the influence of the physico-chemical properties of the soil on the recurrence of flooding in the Mbo plain. Four soil profiles were carried out on the alluviums according to the altitudes. These profiles were described and undisturbed soil samples were taken. Then, measurements of the infiltration rate of water in the soil by the Porchet method were carried out in sixteen sites. Finally, soil samples taken by auger and core sampling were studied in the laboratory. Physico-chemical parameters such as grain size, porosity, moisture, pH, compactness and organic matter were determined. Infiltration tests carried out in situ using the Porchet method revealed a hydraulic conductivity between 10−5 and 10−7 m/s, characteristic of a semi-permeable soil. This low value of permeability results from the morpho-structural arrangement and the chemical composition of the soils of the plain. These soils are hydromorphic, which means that they are constantly flooded and temporarily waterlogged. They are more or less sandy-clay on the surface, and very clayey at depth, generally from 25 cm. The very clayey soils at the base considerably slow down infiltration and act as a real barrier layer that prevents water from infiltrating, resulting to intense runoff. These soils are very porous and compact with a fairly high water content of up to 71%. This work allows us to conclude on the role of intrinsic soil properties on the genesis of floods in lowland areas. As in many plains in Africa and in the world, the nature of the soil in the Mbo plain is a natural predisposing factor to flood risks. The methods used can be applied in areas with the same characteristics as the Mbo Plain.


2021 ◽  
Vol 10 (16) ◽  
pp. e78101623317
Author(s):  
Edsleine Ribeiro ◽  
Priscila Vogelei Ramos ◽  
Tatiele Fruett ◽  
Paulo César do Nascimento ◽  
Estéfane Chaves

Agricultural land use causes changes in physical and chemical attributes of the soil, due to the management practices employed the productive capacity of the soil can be compromised under different agricultural systems. The soils of Porto Alegre are quite diverse reflecting the geology, topography and drainage network of the region, and include lowland soils, like the alluvial plain of the Arroio Dilúvio. This study was carried out in four landscape units (Native Forest, Agroforestry System, Horse Farm and Agricultural Crops), to assess changes in soil characteristics after different types of land use and management on the plain of the Dilúvio Arroio. We sampled disturbed and undisturbed soil samples for chemical (pH, EC, V, SOM, CEC, Al3+, H+Al) and physical analysis (porosity, microporosity and macroporosity). These chemical and physical attributes of the soils, especially pH, V%, SOM, CEC and Al3+, underwent changes under the different types of land use and management, with significant differences. Most changes were detected in the cropland soils. Multivariate analysis demonstrated the influence of the different types of land use, at the surface, land use and management had the greatest influence, while at depth, the proximity of the areas was the predominant factor.


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