Fine Soil Research Articles

Long-term nitrogen-addition-induced shifts in the ectomycorrhizal fungal community are associated with changes in fine root traits and soil properties in a mixed Pinus koraiensis forest

Nitrogen (N) deposition has marked effects on the structure and function of global forest ecosystems. Many forest tree species rely upon a symbiotic association with ectomycorrhizal (ECM) fungi to enhance nutrient acquisition, which affects nutrient and carbon (C) dynamics in forest ecosystems. A better understanding of the characteristics of ECM fungal diversity and composition and their primary determinants under N deposition will help us to identify the mechanisms underlying N-induced effects on forest nutrient and C cycling. In the present study, we explored the effects of long-term N addition (10 years) on the diversity and community composition of ECM fungi identified from fine roots of Corylus mandshurica, Pinus koraiensis and Tilia amurensis in a mixed temperate forest on Changbai Mountain in north-eastern China. We observed that N addition decreased the Shannon and Simpson indices of the ECM fungal community colonizing C. mandshurica and T. amurensis. Neither the Chao1 index nor the observed species richness of the ECM fungal community colonizing the three species was impacted by N addition. Nitrogen addition significantly decreased the fine root and stele diameter of C. mandshurica, and it significantly decreased the cortical thickness of fine roots of both P. koraiensis and T. amurensis. Nitrogen addition had a consistently negative effect on the mycorrhizal colonization of fine roots, but it did not affect the branching intensity of fine roots of the three tree species. Nitrogen addition altered the ECM fungal community composition, which was closely associated with fine root traits, such as mycorrhizal colonization, and edaphic factors, such as soil pH, soil total N concentration and soil CN ratio. An altered ECM fungal community composition was accompanied by shifts in the nutrient acquisition ability, as characterized by exploration types of ECM fungi. These findings have important implications for a better understanding of the effects of a changing ECM fungal community on the C and N cycling of forest ecosystems under increasing N deposition.

Critical hydraulic gradient and fine particle migration of sand under upward seepage flow

In order to study the mechanism of seepage-induced geotechnical damage and characteristics of fine particle migration in sandy soil, a one-dimensional upward seepage test device was used and a series of upward seepage flow tests of sand were conducted. In these experiments, the permeability, fine particle migration and redistribution under different hydraulic gradients were investigated. The results show that local hydraulic gradient in the sand sample is larger than the critical hydraulic gradient calculated by the Terzaghi’s Equation. The seepage force will induce the fine soil particles to migrate along water flow direction and then cause the redistribution and reconsolidation of sand particles. Under the test condition, fine particles (< 0.075 mm) and fine sand particles (0.075–0.25 mm) dominate in the lost soil particles. Soil particles larger than 0.6 mm are hardly to lose.

Checkerboard Barriers Attenuate Soil Particle Loss and Promote Nutrient Contents of Soil

In the arid and semi-arid regions of the world, checkerboard barriers play a vital role in ecological restoration. However, the improvement of soil quality in the later stages of lattice barrier-laying is an issue that is not yet known. This study selected dunes lined with Salix psammophila (SL) and high-density polyethylene (HDPE) checkerboard barriers in the desert zone of an arid zone, and no-barrier dunes were used as the control area. We assessed the soil properties of different dunes’ windward slopes using a combination of particle size characteristics and soil nutrients and using soil nutrients to build a soil quality index (SQI). The laying of checkerboard barriers has a positive effect on the accumulation of fine soil particles and the improvement of soil quality. It ultimately leads to an increase in fractal dimension in the 0–2 cm and 2–4 cm soil layers. SQI and soil nutrients show consistent trends. The SQI of the different dune types follows the order: SL (0.22) &gt; HDPE (0.14) &gt; CK (0.12). We also found an interaction between soil nutrients and particle characteristics through statistical analysis. With a comprehensive assessment of checkerboard barriers installed on dunes, SL can provide better soil restoration benefits.

Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status

Elevated nitrogen (N) deposition may further acidify soils in tropical forests. Yet, we have limited evidence on this prediction and it remained unclear how this would affect fine root growth therein. Here, we report responses of fine root biomass, vitality, and chemistry, as well as related soil parameters to eight years of N additions in three tropical forests different in initial soil N status, with one primary forest being N-saturated, and another two younger forests (one secondary forest and one planted forest) less N-rich. Results showed that in the primary forest, fine root biomass decreased and fine root necromass increased following N addition, resulting in lower live fine root proportion (fine root vitality). Declining fine root vitality was associated with fine root Fe accumulation and soil acidification indicated by regression analysis. These alterations of fine root growth and chemistry co-occurred with soil pH decline, soil exchangeable Fe3+ mobilization, exchangeable Ca2+, and Mg2+ depletion after N treatments in the primary forest. In contrast, N addition only elevated fine root K, Al, and Fe content in the secondary forest. In the planted forest, moderate but significant decreases in soil pH, soil exchangeable K+, and Mg2+ were found after N treatment, with fine root biomass negatively correlated with soil exchangeable Al3+ and Al3+/(Ca2+ + Mg2+) ratio. Our results suggested that long-term N fertilization may negatively affect fine root growth, via severed soil acidification, Fe mobilization, and base cation depletion in highly acidified, N-saturated primary tropical forests. Initial forest N status, influenced by different land-use history, mediates N deposition effects on fine root growth.

Effects of soil surface degradation and vehicle momentum on dust emissions and visibility reduction from unpaved roads

Unpaved roads are built on the basis of soil compaction. Therefore, the operation of vehicles on these roads results in dust emissions. As the number of passing vehicles increases, the soil surface gradually degrades under shearing caused by the tires. This enhances emissions and reduces visibility, increasing health and environmental related issues as well as the risk of collisions.The present study was conducted to quantify the effect of surface degradation on dust emissions from several types of vehicles travelling on different soils and assess the evolution of security risks in the vicinity of unpaved roads.Three types of vehicles (a passenger car, a 4WD vehicle and a truck) have been run on an experimental road covered by four different types of soil particles. Each test consisted in driving one of the vehicles at a given speed (30, 45 or 60 km.h−1) on one of the types of particles previously spread on the road at a given mass per unit area (200, 400 or 600 g.m−2). The mass concentration of resuspended particles was measured from the roadside using an Optical Particle Counter (OPC) while the visibility reduction was simultaneously recorded at the same location. The results show that PM10 emission factors increase linearly with vehicle momentum for vehicles without mud flaps. The presence of such appendices can reduce dust emissions by a factor of 7. Moreover, although not considered in conventional models, the state of degradation of unpaved roads may be a key factor regarding dust emissions. The study has also shown that soils with similar silt content can result in very different emission factors. An emission model has then been developed, based on the clay content of the particles. Indeed, this geotechnical parameter is more relevant to characterize the fine soil propensity to generate dust. PM10 emissions are correlated with the reduction of visibility according to a power law for the truck tests.An interesting finding of this work is the fact that the present results can be extended to earthwork sites where visibility problems require spraying of water on the traffic lanes. Improving the modeling of the mechanisms generating dust lift and the associated safety risks is indeed essential for a more efficient use of water on construction sites.

Soil organic carbon stock capacity in karst dolines under different land uses

The soil organic carbon (SOC) was determined in soils of enclosed karst depressions (dolines) (NW Dinaric Mts.) to define their potential for organic carbon sequestration. SOC was measured in the forest, succession (scrubland), and grassland plots at the bottom of dolines at four depths (0–40 cm) and for 40 cm soil layer SOC stock was calculated. We demonstrated that the prevailing fine soil fractions, the C/N ratio and soil thickness play a positive role in the storage capacity of SOC in dolines regardless land use type. Grasslands have the lowest SOC storage capacity (106 t/ha/40 cm), while the highest SOC storage capacity is in succession plots (130 t/ha/40 cm). The last are covered by shrub communities dominated by Prunus spinosa, forming dense communities, and are typical of abandoned croplands or meadows that have been impacted by high levels of nutrients during cultivation phase. At this stage, there is no additional nutrient input in studied plots, which lowers the nutrient content and increases the C/N ratio. C/N ratio is the highest in the forest, where SOC stock capacity is 116 t/ha/40 cm. Given the trend towards the abandonment of agricultural land at Kras Plateau (SW Slovenia), we can expect more overgrowth of dolines, and thus an increase in carbon stocks and stabilization of organic carbon in forest soils. In contrary, we noticed the alarming decrease in grasslands and increase in urban land. The SOC storage in 2020 was for 12,538 t/ha/40 cm lower than in 2002. Although grasslands showed the lowest SOC storage, their contribution to total SOC storage in dolines is very important. Since there is a lack of studies on carbon stocks in doline soils, our research is of great importance and a novelty and gives an important background for further research on SOC stock in karst landscapes worldwide.

Shear rate effect on the residual strength of saturated clayey and granular soils under low- to high-rate continuous shearing

The residual strength of sliding basal soils plays a pivotal role not only in the movement of bedding landslides controlled by clay-rich interlayers but also in remobilized granular deposits. Many studies have focused on better understanding the residual shear behaviors of clayey and granular soils under relatively low shear rates. However, the residual strength varies with various clay fractions for clayey soils and fine-size fractions for granular soils, as well as shear rates (especially in fast ranges) need further examined. In the present research, results of a low- to high-rate continuous ring shear test on a clayey soil and three granular soils at the shear rates ranging from 0.5 to 50.0 mm/s were reported. The clayey soil was remolded from the shear zone soil of a bedding landslide controlled by a clay-rich interlayer with main minerals of illite-smectite, and the granular soils included two silica sands and one mixture of silica sand with fine granite residual soil particles. The results show that saturated clayey soil has an obvious positive shear rate effect on its residual strength after a certain shear rate; the mechanism is the transformation of shear mode, i.e., from sliding shearing to turbulent shearing with the increasing of shear rate. The high clay fraction may promote this transformation of shear mode. In addition, the critical shear rate of the clayey soil that has a positive shear rate dependency of the residual strength (i.e., rate-strengthening) is related to the clay fraction, i.e., a smaller critical shear rate appears in the clayey soil with higher clay fraction. The residual strength of saturated granular soils with different fine-size fractions do not show any shear rate-dependent, while the fine-size fraction affects the residual strength both in drained and undrained conditions; that is, the higher the fine-size fraction is, the lower the residual strength is. Moreover, the neutral shear rate effect of granular soils in this study may be related to the low normal stress and low shear rate range. The authors believe that, results such as those obtained in this work, may be useful for developing a more suitable constitutive model to better understand the postfailure motion (or reactivation kinematics) of bedding landslides controlled by clay-rich interlayers, as well as rock avalanche deposits remobilized by heavy rainfall.

Improved design criteria for nonwoven geotextile filters with internally stable and unstable soils

In geotextile filtration, the soil fines are either accumulated near the interface, clogged, or washed out, which primarily depends on the grain size distribution (GSD) of soil and the constriction size distribution (CSD) of geotextile. Also, the movement of fines significantly affects the flow capacity of geotextile. Currently, the retention requirement is satisfied based on representative grain and opening sizes, whereas the hydraulic conductivity and clogging requirements are satisfied considering the properties of virgin geotextile. This paper presents a probabilistic retention criterion considering the grain and constriction sizes as random variables. The influence of geotextile thickness is incorporated into the criterion by considering the number of geotextile constrictions in a filtration path. A theoretical approach to predict CSD is presented if the measured data is unavailable. For hydraulic conductivity and clogging requirements, a criterion is presented considering the expected partial clogging of geotextile, which is predicted based on the semi-analytical approach. The limit states for the developed criteria are evaluated based on the wide range of experimental data from the current study and published literature. The developed design criteria are applicable to internally stable and unstable soils, which offers an improvement in design compared to the existing criteria in practice.

Simultaneous removal of suspended fine soil particles, strontium and cesium from soil washing effluent using inorganic flocculants

The purpose of this study was to remove suspended soil, Sr 2 + , and Cs + that may exist in soil-washing effluents using an inorganic coagulant (J-AF). The major chemical constituents of the flocculant J-AF were SO 3 and CaO, and were confirmed to have thenardite (Na 2 SO 4 ), calcium carbonate (CaCO 3 ), and tychite (Na 6 Mg 2 (CO 3 ) 4 (SO 4 )) crystals. When 10 g/L of J-AF was injected into the turbid solution containing unstably suspended soil particles of < 45 μ m , the suspended soil could be completely precipitated. The agglomerates of suspended soil formed using J-AF had a maximum size of more than 1 mm, due to which sedimentation was effective. The precipitation of suspended soil by J-AF was more favorable under acidic conditions, such as pH 2, 3, and 5. Sr 2 + was mainly removed from the supernatant by adsorption using J-AF, and Cs + was precipitated by J-AF while adsorbed on suspended soil and subsequently eliminated from the supernatant. These results provide that J-AF can be used for the simultaneous removal of suspended soil, Sr 2 + , and Cs + from a radioactive soil suspension. • J-AF successfully flocculated and precipitated suspended soil. • Suspended soil precipitated favorably at pH 2, 3, and 5. • Sr 2+ was adsorbed by soil and J-AF, and was partially co-precipitated. • Cs + precipitated while adsorbed onto the soil and separated from the aqueous phase.

Ground improvement by jet grouting and injection to control hydraulic conditions in the frame of Grand Paris Express Project, North-East section: methodology and quality control sequence

The main tunnels of Line 16 Lot1 of the Grand Paris Express project are underway since 2019 using tunnel boring machines (TBM). They are drilled entirely in permeable strata (fine/silty sands, marls, and limestones) at a depth of 20÷30 m below the groundwater level. Groundwater inflow with high pressure is a major issue at the arrival/departure sections of the TBMs as well as during the excavation work of connection galleries between the main tunnels and maintenance or security shafts. Line 16 Lot1 is located under dense urban areas with the requirement of minimizing the drawdown of the groundwater and water inflow in civil engineering works; the purpose is to avoid excessive settlements on existing facilities and dissolution reactivation process of gypsum-rich strata. In order to minimize these risks, different types of ground improvement technics (jet grouting and cement mixture injection) have been applied, where jet grouting is used in fine sandy soil and cement mixture injection used in fissured marly-limestone. In addition, both technics of improvement have been associated on the same site. From a geotechnical point of view, the sands of Beauchamp are classified as coarse-grained soils (60% SM and 40% ML in the Unified soil Classification System ) and Marly-limestone of Saint-Ouen and deep Marls as fissured soft to medium-hard calcareous rock. This paper presents the geotechnical conditions, the ground improvement methodology and quality control during construction. The control sequence is performed by vertical and then horizontal drilling holes. The method of control work after excavation (horizontal control) allows to confirm the quality of the treatment blocks and specifically the bonding between the treatment block and the diaphragm wall.

An Analysis of Surface Water–Groundwater Interactions Based on Isotopic Data from the Kaidu River Basin, South Tianshan Mountain

The unique climate conditions and water source composition in the Tianshan Mountain provide a good experimental site for verifying the relationships between water resources and climate change on a larger scale. With the help of water isotopes (D, 18O), a more reliable conceptual model of groundwater systems can be constructed on both local and regional scales, especially in areas that are susceptible to climate change and under pressure from intensive human activities. In this paper, we present δ18O, δD, d-excess, RWLs and altitude effects of river water and groundwater based on the data derived from our network of stable isotope sampling sites along the Kaidu River. Stable isotope mass balance was applied to study the interactions between groundwater and surface water and to quantify the recharge proportions between bodies of water in typical regions. The results showed that the Kaidu River is composed of precipitation, ice and snow melt, baseflow and groundwater. The percentage of groundwater increased with the distance between upstream (the runoff producing area) and the leading edge of the glacier. The two recharge areas are the spring overflow from the mountain area to the alluvial layer of the inclined plain and the leading edge of the alluvial plains to areas with fine soil. The groundwater recharge ratio is about 23% in high mountain areas but 46% or more in the middle and lower reaches. These results generated a more comprehensive understanding of the hydrological cycle of inland rivers in arid regions.

Atmospheric Conditions for Uplift and Dust Transport in the Latitudinal 10° North–20° North Band in Africa

Desert aerosols suspended in the atmosphere are a very marked fact in West Africa with estimates of 400 to 1000 million tons produced annually and concentrations exceeding 50 µg·m³ in Burkina. In Bamako, the daily dust concentration can go up to reach 504 µg/m³. The Sahara and the Sahel are recognized as the primary desert aerosol producing regions. Source areas continue to be discovered as the desert advances. Previous studies have mainly focused on the spatial and temporal variability of aerosols. The current question is: What makes an area a source of dust emission? Our study brings together all the climatic parameters of the 10–20 band, as well as the soil types and their characteristics; it reveals 4 soils characteristic of fine sandy semi-arid soils in Chad. The Ouadaï plateau in Chad was identified as a source area for dust emissions. We noted for JFM (January, February, March) that the strongest wind intensities were located mainly towards Chad for average rmaximum temperatures around 34.7 °C. The statistical study reveals a correlation of 66.8% between direct and indirect links between the climatic factors of the 10–20 band and the source area. The presence of vortexes throughout the year and a vertical wind profile that is among the strongest in the 10–20 band, this gradient is strongly localized in the grid “10° North, 20° North and 20° East, 30° East” next to the Kapka massif. The study shows that the AEJ (African Easterly Jet) profile, which is a strong wind, associated with the harmattan circulation, allows the transport of aerosols from Ouadaï to the West African coast. In Senegal, a significant deposition was observed.

Correspondence between theory and practice of a Beerkan infiltration experiment

AbstractThe Beerkan infiltration experiment is carried out by inserting the ring a short depth into the soil and establishing a positive head of water on the infiltration surface for at least a part of the run. Nevertheless, the data are analyzed by assuming a fully unconfined infiltration process (ring insertion depth, d = 0 cm) and a null ponded depth of water (H = 0 cm). The influence of ring insertion and ponded water on an infiltration process of 2 h sampled every minute was tested in this numerical investigation. Five soils varying from sand to silt loam, three ring radii (5–15 cm), and the Beerkan‐specific range of values for both d and H (between 0 and 1 cm) were considered. The differences between the theoretical (d = H = 0 cm) and the practical (d = H = 1 cm) setups varied from −10.4 to +8.6% for the mean infiltration rate and from −10.2 to +8.3% for the final cumulative infiltration. These differences were small, and they decreased in absolute value by considering a soil‐dependent ring radius. In particular, nearly negligible differences were detected using a small ring in coarse‐textured soils and a large ring in fine‐textured soils. In the coarser soils, inserting the ring and establishing a ponded depth of water did not alter the estimated coefficients of the two‐parameter infiltration model appreciably with the cumulative linearization method, because these coefficients differed between the theoretical and practical setups by no more than 9.2%. In fine soils, linearization could not be possible regardless of the considered setup, or it was the use of d = H = 1 cm instead of d = H = 0 cm that impeded a convincing linearization of the data. In conclusion, the good correspondence, in many circumstances, between the theoretical and the practical Beerkan infiltration experiment reinforced the interest in this simple experiment as a practical means to collect infiltration data in the field.

A novel resistivity measurement method for a homogeneous cylinder shape based on the vdP configuration

The electrical resistivity method for a cylinder shape is an essential method for reflecting physical properties. However, the use of a nondestructive resistivity method with the circumferential cross-section arrangement for working components remains challenging. This paper provides a simple novel resistivity method for a cylinder shape based on the van der Pauw configuration, with four electrodes placed near the middle cross-section layer of shape. First, the theoretical solution formulae for the electrostatic potential function in the cylindrical coordinate system are derived. Then, the effect of the electrode and shape size is analysed. The results show that the electrode height is less than 1% of the cylinder height and the radian angle is less than 10°, where the electrode size effect on the correction factor (CF) can be ignored, and CF rarely depends on the cylinder shape. Finally, a prototype is designed, and the proposed method is verified in laboratory tests using geomaterials. The performance of the proposed method for fine soil at high moisture contents is found to be better than that at low moisture contents.

Variable Significance Determination Utilizing Extended CHAID Method in Fiber Improvement of Fine Soils

Variable Significance Determination Utilizing Extended CHAID Method in Fiber Improvement of Fine Soils

Fine Soil Texture Is Conducive to Crop Productivity and Nitrogen Retention in Irrigated Cropland in a Desert-Oasis Ecotone, Northwest China

Agricultural production in oases requires extensive irrigation and nitrogen (N) inputs, which result in a high incidence of non-point-source pollution. Information on how soil texture affects crop productivity and water and N use efficiency is needed to improve N management in oases. A two-year field study with six free-draining leaching pits was set up to quantify soil water content (SWC), drainage, yield, N uptake, soil residual N, N leaching, water-use efficiency (WUE), and N fertilizer-use efficiency (NFUE) on sandy-textured soils in a young oasis field (24 years, YOF) and loam-textured soils in an old oasis field (&gt;60 years; OOF) within an intensive oasis agricultural zone in Northwest China. The results showed that sand content in the YOF was significantly higher than that in the OOF (p &lt; 0.01), while both clay and silt contents in the YOF were significantly lower than those in the OOF (p &lt; 0.01). Soil water storage (SW) in the 0–100 cm soil layer, evapotranspiration water-use efficiency (WUEET) and irrigation water-use efficiency (WUEIrrig) in the OOF were, respectively, 87.1, 23.5, and 24.1% higher than those in the YOF (p &lt; 0.05), and deep drainage in the YOF was 6.2 times higher than that in the OOF (p &lt; 0.01). Maize N uptake and soil N accumulation in the OOF in the 0–100 cm soil layer were, respectively, 33.4 and 10.3% higher than those in the YOF (p &lt; 0.05), and N leaching loss in the YOF was 1.65 times higher than that in the OOF (p &gt; 0.01). Crop yield and NFUE in the OOF were, respectively, 23.9 and 27.2% higher than those in the YOF (p &lt; 0.05). These results indicated that sandy-textured soils with high sand content were not conducive to water and N retention, resulting in lower crop yields and water- and fertilizer-use efficiency in YOF. Therefore, it is imperative that management practices in sandy-textured land promote improvements in soil structure and maintain the long-term productivity of the young cultivated fields.

Interactive Effect of Biochar and Bio-Compost on Starting Growth and Physiologic Parameters of Argan

The argan tree, which is found in southern Morocco, is characterized by environmental, economic and nutritional benefits, but the growth of this tree is very slow. This makes it necessary to find methods to accelerate its growth. A pot experiment was conducted to evaluate the effects of biochar (BC) and bio-compost (CP) each applied at the rate of 0, 3 and 6% (M/M) on starting growth of argan in fine silty soil for sixteen months. Main stem length, diameter, durability ratio, total length of all stems and number of sprouted shoots were measured every two months with two photosynthetic measurements spaced five months apart for each argan seedling. Despite the strong signs of epigenetic sensitivity and genetic variability across the argan behavior of each treatment depending on the duration and environmental conditions of the crop and the large standard deviations marked in all the tests that were conducted on the argan, some treatments showed interesting results, even in terms of the interaction between climatic conditions, type of treatment and type of test. The argan plants which were grown in the substrate at 6% BC 3% CP showed significant results for all the growth parameters studied and throughout the test. This mixture marked an average water holding capacity (WHC) of around 0.66 g H2O/g dw; the argan seedlings showed the best perimeter average, which exceeded 2.7 cm in the last measurement, with a ratio (height/diameter) strictly less than 7, which removes any possible problem of argan filiform. However, argan plants from all treatments were not stable in the growth characteristics studied; each treatment has advantages and disadvantages regarding argan. Transplantation and monitoring in the field of argan seedlings that have had interesting results are strongly recommended to see if the good starting growth influences their development in the field or if it is a temporary effect.

What Influence Does Conventional Tillage Have on the Ability of Soils to Sequester Carbon, Stabilise It and Become Saturated in the Medium Term? A Case Study in a Traditional Rainfed Olive Grove

Soils have the capacity to store three times more carbon (C) than the atmosphere. This fact has focused scientific and governmental attention because it is one way to mitigate climate change. However, there comes a time when the capacity of soils to store C reaches a limit, considering soil organic carbon (SOC) saturation. In the Mediterranean area, agricultural soils are traditionally exposed to conventional tillage (CT), causing soil properties and quality degradation. Therefore, this study aimed to determine whether CT modifies the carbon storage capacity (carbon saturation), linked to soil mineral fractions &lt;20 µm in olive grove soil in a Mediterranean area over 15 years. The results showed losses of SOC and soil organic carbon stock (SOC-S) over the period studied. Moreover, CT significantly affected aggregate grain size, reducing the percentage of small macro-aggregates (2000–250 µm) by 51.1%, 32.9%, 46.6%, and 50.6% for the Ap, Bw, BC, and C horizons, respectively, and promoting an increase in fine fractions (large micro-aggregates (250–53 µm), silt + clay fraction (53–20 µm) and fine silt + clay (&lt;20 µm)). After 15 years, SOC fractionation showed a decrease in SOC concentration within the large macro-aggregate fraction (&gt;2000 µm) of 38.6% in the Bw horizon; however, in the small macro-aggregates (2000–250 µm), an increase in SOC concentration over time, of 33.5%, was observed in the Ap and Bw horizons. This increasing trend continued in the fine soil fractions. Concerning SOC bound to the fine mineral fraction (&lt;20 µm), evolution over time with CT led to an increase in soil sequestration capacity in the first horizons of 44.7% (Ap horizon) and 42.9% (Bw horizon), and a decrease in depth (BC horizon) of 31.3%. Finally, the total saturated soil organic carbon stock (T-SOC-Ssat), after 15 years, experienced an increase of 30.5 Mg ha−1, and these results conditioned the soil organic carbon stock deficit (SOC-Sdef), causing a potential increase in the capacity of soils to sequester carbon, of 15.2 Mg ha−1 in 15 years. With these results, we can affirm that the effect of CT in the medium term has conditioned the degradation of these soils and the low SOC concentrations, and has therefore made it possible for these soils, with the application of sustainable management practices, to have a high carbon storage capacity and become carbon sinks.

Study of the relationship between the fundamental properties of fine soils and those of mathematical models of particle size distribution and geotechnical quantities

Study of the relationship between the fundamental properties of fine soils and those of mathematical models of particle size distribution and geotechnical quantities

Investigating the effect of the tractor driving system type on soil compaction using different methods of ANN, ANFIS and step wise regression

Farm tractors have different driving systems, including four-wheel drive and rear-wheel drive which are common systems employed to conduct agricultural operations all over the world. The type of driving system influences tractor wheel slip which is one of the most effective factors in soil compaction. Hence a series of experiments were conducted using Goldoni 240 tractor to investigate the effects of tractor driving systems, including four-wheel drive (4WD), rear-wheel drive (RWD), and front-wheel drive (FWD) at different travel speeds, soil moistures, number of passes (1, 5, and 9), and soil textures (clay loam, loam, and sandy loam) at the depths of 10, 20, 30, and 40 cm. Increasing tractor wheel slip showed a significant effect on increasing soil compaction. The lowest tractor wheel slip was occurred using the 4WD system, and by increasing travel speed in this system, soil compaction decreased. Increasing tractor speed in the FWD system increased tractor wheel slip and soil compaction. In addition, increasing soil moisture content resulted in an increase in soil compaction, and this event was intense in fine soils like clay loam. It was found that adaptive neuro-fuzzy inference system (ANFIS) higher potential to predict the effect of multiple input variables on soil compaction (R2 =0.99) than regression method. According to the standard coefficients of regression models, depth, type of driving system, number of passes, moisture content, texture, speed, and inflation pressure were the factors significantly influencing soil bulk density, respectively.