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Evaluating the liquefaction capacity of saturated loose sandy and clayey soils is an important task to be completed in the course of implementing new construction projects in seismic areas. This article addresses the main characteristics and input parameters of three soil models, including HS small, UBC3D-PLM, and PM4Silt. The behavior of the "soil base–pile foundation–structure" system is examined by using these models to simulate the soil behavior during an earthquake. The results demonstrate the main differences between these models and draw attention to the importance of the choice of a soil model for seismic analysis, particularly when soil liquefaction is considered. [ABSTRACT FROM AUTHOR]

Sesame (Sesamum indicum L.) is an oilseed crop flourishing in marginal lands. It has a high nutritional value because it is rich in protein and fat and has many health benefits. However, the varieties of this crop available in Egypt are very few. Seventeen new sesame lines incurred evaluation in two crop seasons, 2021-2022, for seed yield under eight environments comprising normal and drought conditions in sandy and clay soils. Applying 16 parameters and non-parameters of stability helped select stable and adaptive sesame lines under ideal and drought conditions, with the genotypes arranged in a randomized complete block design with three replicates. Line C5.8 achieved the highest relative productivity in sandy and clay soils and exhibited a good source for breeding programs under drought conditions. Four lines, C1.3, C9.15, C9.6, and C9.20, under eight different environments had higher seed yield than the control. A genetic-environment interaction (GEI) effect on seed productivity occurred in all sources of the combined analysis. The association between seed yield and stability parameters showed the possibility of using a selection index that included some of them to identify sesame genotypes with higher yield and genetic stability. [ABSTRACT FROM AUTHOR]

The piezocone penetration test (CPTu) is a common geotechnical field test to evaluate soil properties. In interpreting the CPTu field measurements, soil drainage conditions are mostly considered completely drained or undrained; however, partial drainage conditions govern for such soils as silts or clayey sand mixtures. Previous studies show that neglecting partial drainage conditions causes incorrect estimation of soil geotechnical parameters. Most studies have been conducted using calibration chambers and centrifuge tests on clayey soils. Due to the complications in modeling the piezocone test, few numerical studies have been performed under partially drained conditions, especially on coarse-grained soils. Among the challenges of numerical modeling of CPTu, one can mention the difficulty of modeling soil structure in large strain mode and soil–water interaction behavior. In this paper, piezocone penetration tests were modeled using the advanced hypoplastic constitutive model and finite-element method. The behavior of Firoozkooh sandy soil under different drainage conditions and relative densities was analyzed. Then, the effect of cone penetration on the surrounding soils was discussed. It was shown that drainage conditions and the soil relative densities significantly affected the trend of variations in excess pore-water pressure (EPWP) generated around the piezocone. [ABSTRACT FROM AUTHOR]

Eucalyptus (Eucalyptus spp.) leads to depletion of nutrients from the soil due to its fast growing nature. Therefore, a pot experiment was conducted to study the effect of zinc (Zn) application on clonal eucalyptus growth, biomass output and its uptake, as well as response of eucalyptus to Zn in soils of three textures. The treatments consisted of eight levels of Zn (0, 5, 10, 15, 20, 25, 30, and 35 mg kg−1 applied through ZnSO4.H2O) in a completely randomized design triplicated in soils of three distinct textures (loamy sand, sandy loam and sandy clay). The plant height, collar diameter, dry weight of shoot and roots, soil plant analysis development (SPAD) readings, Zn concentration and uptake by leaves, stem+branches and roots increased significantly with Zn application. Average dry weight of shoot and roots (31.93 and 15.12 g plant−1, respectively) was significantly highest at 15 mg Zn kg−1 whereas Zn concentration and uptake (18.35 mg kg−1 and 286.2 µg plant−1, respectively) by roots were highest at 20 mg Zn kg−1. The above parameters differed significantly among soils as sandy clay>sandy loam>loamy sand except Zn content and uptake by roots and SPAD values which were highest in sandy loam soil. Loamy sand and sandy loam soil exhibited higher Zn use efficiency, shoot biomass response and uptake response to applied Zn than sandy clay soil. It is concluded to apply 20 mg Zn kg−1 in light soil and 15 mg Zn kg−1 in heavy textured soil for better growth and productivity of eucalyptus. [ABSTRACT FROM AUTHOR]

The agricultural frontier in Brazil advances mainly in areas of sandy soils, where the management of soil fertility is still a challenge, including the practice of liming. Limestone dissolution was investigated under varying doses (0–40 t ha−1) in soil samples with a wide range of textural gradients (5%–74% clay). In view of textural variations and limestone rates, the objective was to generate information regarding pH, the residual liming effect, and exchangeable calcium (Ca) and magnesium (Mg) levels, including under overliming conditions. Throughout the textural gradient, the pH was between 4.2 and 8.5. On more sandy soils (5%–18% clay), overheating (pH > 7) was obtained with ~ 2 t ha−1 of limestone. On clayey soils (37%–74% clay), a similar effect was obtained with ~ 10 t ha−1 of limestone, indicating the marked difference in the acid buffering capacity of these soils. In addition, the equilibrium pH in the context of overliming in sandy soil was higher (8.2) compared with clayey soils (7.8). The residual liming effect was greater in sandy soils due to the lower potential acidity. Regardless of the soil texture, the Ca/Mg ratio increased in the context of overliming. Liming must be carefully applied and requires proper recommendations, especially on sandy soils, avoiding pH ≥ 6.5, a condition that is not suitable for most crops. [ABSTRACT FROM AUTHOR]

The timing of nitrogen fertilizer application in vineyards can determine the amount of nitrogen (N) absorbed, distributed, and accumulated in grapevine organs. The study aimed to evaluate the annual contribution of N from urea, applied at different times in Cabernet Sauvignon, grown in sandy and clayey soil in a subtropical climate. The sandy soil received 21.42 kg N ha−1 and the clayey soil 30 kg N ha−1, both enriched with 3% excess 15N atoms, applied at different times. The N derived from the fertilizer in grapevines, at all times of N application, and in sandy and clayey soil did not exceed 8%, with the highest values being observed in annual organs, especially in the leaves. The application of N marked at the phenological stages of IBB (50% at beginning of budbreak + 50% at full budbreak) enabled greater absorption of N derived from the fertilizer by the vines grown in both sandy and loamy soil. The N present in the annual organs (leaves, berries, stalks, and shoots) and in the perennial organs (stems and canes) of Cabernet Sauvignon grown in sandy and clayey soil was derived in greater percentages from the soil. [ABSTRACT FROM AUTHOR]

Tomato is valued for its nutritional importance and contribution to countries' GDP. Despite the importance of tomatoes, tomato cultivation remains a challenge in some cities, particularly Kumba, Cameroon. This results from a vast knowledge gap for a suitable variety and agronomic management practices. Thus this work was set out to investigate the response of three tomato varieties under organic, foliar, and granular inorganic fertilization at the Kumba I subdivision. This work comprised two factors; variety having three levels (Cobra F1, Rio Grande, and Kiara tomato varieties) and fertilization having four levels (control, NPK 20:10:10 granular fertilizer, Foliar NPK 20:10:10 inorganic fertilizer, and Poultry manure) given twelve treatment combinations replicated three times randomly in a factorial design. Data was collected on soil physicochemical properties, plant growth parameters and fruit yield. The results showed that the variety did not significantly affect soil physicochemical properties, but soil physicochemical properties were significantly affected by fertilization. Poultry manure had the best OC (5.22 %), Ntot (1.73 g/kg), and Pavail (14.63 mg/kg), while K was highest (2.93 meq/100g) in NPK 20:10:10 granular fertilization. Rio grande, in combination with poultry manure, had the best plant growth; plant height (77.3 cm), number of branches (17), number of leaves (197), and leaf area (47.1 cm2). Cobra F1, in combination with foliar NPK 20:10:10 granular and poultry manure, had the best fruit yield; 13.42 tha-1 and 13.56 tha-1, respectively while Kiara variety at the control treatment had the lowest yield (8.36 tha-1). Thus Cobra F1 variety in combination with poultry manure yielded the best result from this study and offers the best option for tomato cultivation in the sandy clay soils of Kumba, Cameroon. [ABSTRACT FROM AUTHOR]

Interactions between adjacent piled-raft foundations may induce additional settlement and cause the tilt of the structure. This case study investigates the long-term performance of a large piled-raft foundation system supporting high and heavy alumina solution storage tanks based on field measurements and three-dimensional (3D) numerical simulations. To properly consider the interactions among rafts, piles, and soils; the elastoplastic behavior of clayey and sandy soils; and the consolidation behavior of soil after construction, a 3D finite-difference code was utilized for the numerical modeling. Two undrained mechanical analyses were conducted to simulate the installation of foundations/tanks and the filling of alumina solution into the tanks, while two coupled hydromechanical analyses were performed to model the period between the two undrained stages and the stage after tank filling, respectively. The predictive capability of the numerical model was checked by comparing the simulation results first with single pile load test data and then with in situ settlement measurements at different locations of the piled-raft foundations. The long-term behavior of the piled-raft foundations was further investigated by analyzing various aspects including the axial force variation along the pile at different locations, the time-settlement relation at monitoring locations, the vertical effective stress increment and displacement of soil, and the differential settlement between monitoring locations. Based on the simulations, the tilt of the platform was mainly due to the superposition of additional stresses near the centerline of the two rows of piled-raft foundations. Finally, parametric studies were conducted to investigate the interactions among the piled-raft foundations at different pile length configurations. The results show that by properly increasing the length of the piles near the centerline of the two rows of piled-raft foundations, the differential settlement of the platforms can be mitigated. [ABSTRACT FROM AUTHOR]

Current ware potato yields in the Netherlands are approximately 70% of their potential. It is hypothesised by several stakeholders within the potato value chain that part of the potato yield gap is caused by a lack of phosphorus (P) and potassium (K) application. In this study, we analysed for 46 farmers' fields if increasing P and K fertiliser application rates led to a higher yield and yield quality. We found that, on average, increased P and K fertiliser application did not result in a significantly higher yield for two currently cropped potato cultivars on two different soil types in the Netherlands (Innovator on clay soils and Fontane on sandy soils) and in two years (2019 and 2020). However, on sandy soils at relatively lower farmer K application rates, our K application led to a small positive yield response up to 5 t ha−1. On clay soils, there was an average positive yield response to our K application at lower yield levels of the control. For P, we did not find any correlation between yield response to P application and the amount of P applied by farmers or any of the measured soil parameters. In terms of yield quality, the K application led to a slight reduction in underwater weight on sandy soils in 2019 and a slight increase in the yield of large tubers in 2020. We conclude that, although in some fields there was a small positive yield effect of increased K application, increasing P and K application rates will not narrow the potato yield gap and improve potato yield quality in the Netherlands. Instead, increasing the P and K application will decrease P and K use efficiency and hence is not recommended from an environmental and economic perspective. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) emissions affect the environment, the climate, and human health and originate mainly from agricultural sources like urea fertilizers. Such losses from urea fertilizer can be avoided by different application techniques like incorporation. However, the knowledge of the effect of these techniques on NH3 emissions is very limited and ambiguous since incorporation can also promote nitrous oxide (N2O) emissions. Three different principles of fertilizer incorporation methods were compared in three different soils (sandy, loamy, and clayey) at two moisture levels of 70% and 30% water-holding capacity (WHC), shallow mixing at 2 cm, injection with the slit technique at 5 cm, and deep complete incorporation at 5 cm simulating plow incorporation. The laboratory study was conducted with open dynamic incubation chambers where NH3 emissions were monitored with washing bottles while N2O emissions were studied with gas chromatographic (GC) measurements. The highest cumulative NH3 emissions occurred at low soil moisture levels in sandy soil (34% of the N applied). A maximum reduction in emissions by 87% was achieved with slit injection and 82% with deep injection compared to standard surface application. The reduction effect was positively related to increasing clay content. N2O emissions were delayed and highest from sandy soil. Overall, all urea incorporation techniques showed great potential for mitigating NH3 emissions on the clayey soil; for sandy and drier soils, only deeper or closed slot injection were consistently effective. However, connected to the surface incorporation at the higher moisture level, a relevant increase in N2O emissions compared to surface application was observed. Therefore, an increase in N2O emissions by urea incorporation may rule out specific incorporation techniques for NH3 emissions reduction from field-applied urea. In agricultural practice, a lower reduction in NH3 by fertilizer incorporation can be assumed in sandy soils or under dry soil conditions, as well as a more challenging technical implementation. [ABSTRACT FROM AUTHOR]

Abstract—The response of sandy and clay subsurface soils, representing classes of non-cohesive and cohesive soils, during seismic motion of various intensities is analyzed based on the in situ observations—records by seismic vertical arrays of the Japanese strong motion network KiK-net. From a total of ~800 stations, five stations with sandy and five stations with clayey subsurface soils represented in the upper layers in their purest forms were selected for the analysis. For sandy and clayey stations, models of soil behavior during strong motion were constructed by the method of (Pavlenko and Irikura, 2003), showing vertical distributions of stresses and strains induced by strong motion in soil layers; and the behaviors were compared. Similar estimates of the amplification of seismic waves in sands and clays during weak motions and similar stress-strain relations describing the behavior of subsurface soils during moderate seismic motions are obtained. The liquefaction of sandy soils during strong motions (the 2011 Tohoku earthquake, Mw ~ 9.0) and the effects of extended seismic source (the directivity of seismic radiation) on the behavior of sandy and clayey soils and amplification of seismic waves are analyzed. Differences in the behavior of sandy and clayey soils are observed only during strong motions, namely, liquefaction occurs in sandy soils (when the groundwater level is about several meters from the surface), but never in clayey soils. [ABSTRACT FROM AUTHOR]

In this paper, a constitutive model is presented to model the behavior of various soils (sand and clay) in different loading conditions and the minimum required parameters are obtained. Although some practical features (concepts) of the bounding surface framework and modified Cam-Clay have been employed in its formulations, the model is developed mainly based on the generalized plasticity framework. Moreover, some concepts such as dilatancy relation and loading history surface are redefined. Finally, the proposed constitutive model is evaluated using the experimental data related to two different sandy soils and three different clays under different loading conditions. Finally, it is concluded that the proposed constitutive model can easily be calibrated for various clayey and sandy soils. It can depict different behavioral aspects of these soils under different monotonic and cyclic loading conditions. [ABSTRACT FROM AUTHOR]

The effect of amending "barren" sandy and clay soils with different organic origins on soil organic carbon (SOC) accumulation and permeability is not well known. Therefore, proposing desirable practices to improve their qualities and fertility is a major challenge. To improve soil organic carbon, permeability (PR) and productivity, the two barren soil textures were amended with 0.39 and 0.78 tha−1 (ton per hectare) of manure and lignite, respectively, and irrigated with treated wastewater. During the four years of experimentation, the ranges of increase in SOC of sandy and clay soils were 1.9–3.87 kgm−2, and 0.29–1.40 kgm−2, respectively, and in PR of 35.2–69.3% in sandy soils and 39.3–74.8% in clay soils. These improvements have a major effect on nutrient cycling, significantly improving water and nutrient availability to roots and plants. The levels of improvement increase with the amounts of organic compounds introduced, especially in the clay soil amended with 0.78 tha−1. The proportions of mineralized (lost) SOC were 35.3–62.3% in the sandy soils and 1.0–3.1% in the clay soils. The maximum crop weights produced were approximately 41.2 gm−2 in sandy soils and 1152 gm−2 in clay soils. Thus, amendment of barren sandy and clay soils by all three sources of organic carbon was beneficial, especially for the clay soil. achieved the desired objectives. The gain in clay soils is significantly greater than in sandy soils, which require further study. The type of practice desired by farmers will depend on cost and crop yield. Laboratoire Géoressources. Univerversité de Carthage-Centre des Recherches et Technologies des Eaux, B.P. 273, Soliman 8020 (Tunisia). [ABSTRACT FROM AUTHOR]

A wrap-faced embankment model on soft clay soil subjected to earthquake motion was investigated in this study. The study was conducted both experimentally using a shaking table and numerically using PLAXIS 3D software. The amplification of acceleration, displacement, pore water pressure, and strain response were measured while varying input accelerations and surcharge pressures. Time histories of the Kobe record of the 1995 Hanshin earthquake were used as the input seismic motion. The input acceleration was 0.05 g, 0.1 g, 0.15 g, and 0.2 g, and different surcharge pressures were 0.70 kPa, 1.12 kPa, and 1.72 kPa with relative density of Sylhet sand fixed to 48%. The output data from the shaking table tests and the numerical analysis performed through the PLAXIS 3D software were compared, and these findings were also compared with some earlier similar studies. The acceleration amplification, displacement, pore water pressure, and strain (%) changed along the elevation of the embankment and acceleration response increased with the increase in base acceleration. The increase was more noticeable at higher elevations. These findings enrich the knowledge of predicting the dynamic behavior of wrap-faced embankments and enable the design parameters to be adjusted more accurately. [ABSTRACT FROM AUTHOR]

This study evaluates a binary mixture of fly ash and lime as a stabilizer for natural soils. A comparative analysis was performed on the effect on the bearing capacity of silty, sandy and clayey soils after the addition of lime and ordinary Portland cement as conventional stabilizers, and a non-conventional product of a binary mixture of fly ash and Ca(OH)2 called FLM. Laboratory tests were carried out to evaluate the effect of additions on the bearing capacity of stabilized soils by unconfined compressive strength (UCS). In addition, a mineralogical analysis to validate the presence of cementitious phases due to chemical reactions with FLM was performed. The highest UCS values were found in the soils that required the highest water demand for compaction. Thus, the silty soil added with FLM reached 10 MPa after 28 days of curing, which was in agreement with the analysis of the FLM pastes, where soil moistures higher than 20% showed the best mechanical characteristics. Furthermore, a 120 m long track was built with stabilized soil to evaluate its structural behavior for 10 months. An increase of 200% in the resilient modulus of the FLM-stabilized soils was identified, and a decrease of up to 50% in the roughness index of the FLM, lime (L) and Ordinary Portland Cement (OPC)-stabilized soils compared to the soil without addition, resulting in more functional surfaces. [ABSTRACT FROM AUTHOR]

To achieve the carbonization utilization of Triarrhena lutarioriparia straw and relieve the environmental pressure caused by improper disposal in the Dongting Lake area, the agricultural efficiency of biochar derived from Triarrhena lutarioriparia was clarified. Two typical paddy soils in southern China, namely reddish clayey soil developed from a Quaternary laterite parent material and granitic sandy soil developed from a granite parent material, were selected. Six treatments with different dosage of biochar (0, 1%, 2%, 4%, 6%, and 8% of the soil mass，0-20 cm soil depth) were set. Rice pot experiments were conducted in 2020 to study the effects of different application rates of Triarrhena lutarioriparia biochar on rice nutrient utilization characteristics in two typical soils. The results showed different application rates of Triarrhena lutarioriparia biochar and soil types had certain effects on dry matter accumulation and nutrient uptake by rice organs and aboveground structures. With the addition of biochar, compared with the treatment without biochar, the accumulation of dry matter of rice increased from 0.6% to 18.6% and from 15.5% to 42.4% in the granitic sandy soil and reddish clayey soil, respectively. With the addition of 4% biochar, the accumulation of nitrogen, phosphorus, and potassium nutrients in the rice plant of the treatment increased by 8.6%, 10.5%, and 82.5% in the granitic sandy soil and by 33.8%, 100.0%, and 125.3% in the reddish clayey soil, respectively. The quadratic regression equation and fertilizer – carbon coupling model fitting showed that the optimal addition amounts of biochar in the granitic sandy soil and reddish clayey soil were 2.51% and 4.80% for nitrogen utilization, 4.33% and 7.03% for phosphorus utilization, and 4.67% and 4.81% for potassium utilization, respectively. Therefore, the application of Triarrhena lutarioriparia biochar is conducive to promoting the accumulation and growth of nitrogen, phosphorus and potassium nutrients in rice, and the amount of biochar added and soil conditions are important factors affecting the coupling effect of fertilizer and carbon. [ABSTRACT FROM AUTHOR]

Bioremediation has been proven to be efficient method of cleaning up oil contaminated soils through the application of proper microorganism to contaminated soils. Hence, this research involves the bioremediation of four different types of contaminated soil. The soils were categorized as laterite, sandy soil, clay soil, and loamy soil which are classified technically using American Society for Testing and Materials (ASTM) method as clayey sand, silty sand, clayey sand and poorly graded sand respectively. These soils were contaminated with Bonny light crude oil to the concentration of 33.3 g/l. The soils were inoculated with petroleum remediation microorganisms. Soil samples were taken after 14 and 25 days, and the residual total petroleum hydrocarbon (TPH) was checked using Environmental Protection Agency (EPA) Method 8015. The condition of the soils was kept almost constant during the process by preserving it in an insulated vessel to avoid evaporation of moist or organic gases. The results obtained showed percentage reduction 70%, 69%, 49%, and 26% in hydrocarbon after the period of 25 days in Sand, Laterite, Topsoil and Clay soil respectively. The removal percentage was the highest (70%) for the sandy soil, and the lowest for the clay soil (26%). The result indicate that the particle size distribution of soil affects bioremediation to an extent, since clay with lowest particle size proved more difficult to bio-remediate. [ABSTRACT FROM AUTHOR]

Purpose: Polyphosphate (poly-P) fertilizers were proposed to increase the low phosphorus use efficiency (PUE) of orthophosphate (ortho-P) fertilizer but empirical data is inconsistent. Our study is aimed at investigating how soil properties, application time, and growth duration affect their phyto-availability. Methods: Olsen-P dynamics were monitored using six soils amended with either ortho-P or poly-P. Subsequently, two contrasting soils (sandy and loamy) were selected to estimate P availability to plants using wheat as a model plant. Mechanistic modelling was used to interpret P dynamics in these experiments. Results: For poly-P amended soils, Olsen-P increased continuously, while using ortho-P fertilizer the highest values were attained right after application and then monotonously decreased afterward. Olsen-P dynamics varied greatly among soils depending on their sorption capacity and related properties. In sandy soils, Olsen-P was consistently higher for ortho-P. In highly calcareous soils, Olsen-P was higher for poly-P after three weeks. Plant experiments confirmed a greater uptake of poly-P over ortho-P in loamy soil and extended trials (4 months) but not in sandy soils or short-term trials (4 weeks). Geochemical modeling suggested that complexation of soil Ca by poly-P reduced long-term P immobilization. Conclusions: Soil properties and growth duration affect the efficiency of ortho-P vs. poly-P fertilizers. In clayey soils and extended growth duration, poly-P fertilizer can enhance PUE due to its prolonged phyto-availability as compared to ortho-P. In sandy soils and short growth duration poly-P has little advantage. The complexation of Ca by poly-P may have caused the increase of P phyto-availability. [ABSTRACT FROM AUTHOR]

This paper addresses a soil bio-stabilization technique using bacterial enzyme-induced calcium carbonate precipitation (BEICP) as an alternative to previous conventional methods including microbial-induced carbonate precipitation and plant-derived enzyme-induced carbonate precipitation. The extracted urease enzyme of viable S. pasteurii was used as a biological source along with calcium chloride and urea to solidify sandy soil and silty sand soil. The bio-treated soil columns were subjected to freeze and thaw (F–T) cycling for a durability evaluation. Engineering properties of bio-cemented soil including unconfined compressive strength, calcium carbonate contents, moisture contents, porosity, permeability, and microstructure were examined before and after the F–T durations. It was found that although bio-stabilizer was able to increase a frost duration of soil, the F–T cycling significantly impacted on the compressive strength of bio-treated soil, due to a formation of microcracks. This investigation has revealed that the BEICP method provided a similar capacity in F–T resistance of soil as using the traditional Portland cement stabilizer, whereas the class F fly ash did not improve F–T durability of medium dense soil. [ABSTRACT FROM AUTHOR]

Compressed stabilized soil block is a sustainable building material primarily made up of stabilized damp soil compressed under pressure. Soil properties and the type of the stabilizer used in producing compressed soil blocks have a significant impact on the quality and behavior of the soil blocks. This study presents the physical and mechanical behavior of lime-cement-stabilized compressed interlock soil blocks produced from two types of natural soil. The two types of soil have different index properties and mineral oxide compositions. Lime-cement combination and cement standalone was used as a binder in the production of test sample blocks depending on the index properties of the soil. 2%lime + 6%cement, 3%lime + 8%cement, and 4%lime + 10%cement were used for the soil block produced from silty clay soil of medium plasticity index. On the other hand, 6%, 8%, and 10% cement by dry mass of soil were used to stabilize silty sand soil. The behaviors of the blocks, such as dry density, the initial rate of water absorption, saturated absorption of water, compressive strength, and stress-strain relation, were examined. The result shows that the compressed soil blocks produced from lime-cement-stabilized silty clay soil has a low rate of initial water absorption and a low dry unit weight when compared to cement-stabilized sandy soil blocks. Soil blocks produced from cement-stabilized silty sand soil attain greater compressive strength by more than 50% of the compressive strength of silty clay soil blocks stabilized by a combination of lime and cement at 60 days after production. The initial tangent modulus of the soil blocks produced using a manual compressing machine from a clay soil stabilized by the lime-cement proportions of 2%L + 6%C, 3%L + 8%C, and 4%L + 10%C is about 1,700 MPa–2,300 MPa with a dry density greater than 1,660 kg/m3. [ABSTRACT FROM AUTHOR]

The priming effect (PE) induced by exogenous organic substrate input plays an important role in the soil carbon balance. However, little is known about how the chemical complexity of different exogenous organic substrates and soil type regulate the PE. Therefore, we conducted a 72-day incubation experiment involving the addition of three 13C-labelled substrates (glucose, starch and cellulose) to two forest soils with contrasting textures (i.e., a fine-textured clay soil and a coarse-textured sandy soil). Cellulose had a lag phase in the mineralization process but induced greater PE compared to glucose and starch in both soils. Moreover, exogenous organic substrate input generally induced negative PE and net soil C gain in the clay soil, but positive PE and net soil C loss in the sandy soil. The negative PE in the clay soil was negatively correlated with exogenous C mineralization, indicating that preferential substrate utilization was the mechanism controlling PE in the clay soil. However, the positive PE in the sandy soil was positively correlated with exogenous C mineralization, microbial biomass C (MBC), cellulase activity and soil inorganic N content, suggesting that co-metabolism was the mechanism regulating PE in the sandy soil. The significant difference in PE between the clay and sandy soils was mainly attributed to their significant differences in soil MBC, dissolved organic C (DOC) and SOC contents, followed by soil texture (particularly the clay content), available N content and pH. Overall, our results demonstrate that soil type is much more important than substrate type in regulating the PE and that the clay soil has a greater C storage potential than the sandy soil following the input of exogenous organic substrates. [ABSTRACT FROM AUTHOR]

Co-application of fertilisers and biofertilisers increases solubility and concentration of nutrient elements in the soil. However, information on the effect of P fertiliser and rhizobium inoculation on the concentration of mineral elements in the rhizosphere of field-grown chickpea in contrasting soil types is lacking. We assessed the effect of phosphorus fertiliser, rhizobium inoculation, and rhizobium inoculation plus P fertilizer on the concentration of nutrients in the rhizosphere of 2 chickpea genotypes (ACC#1 & ACC#5) at clay and sandy soil sites in two consecutive years. ACC#5 accumulated higher amounts of rhizospheric nutrients than ACC#1 in both soil types despite the variable response to fertiliser treatment. Rhizobium inoculation plus P fertiliser resulted in higher accumulations of rhizosphere N (7-219%), P (20-348%), K (9-365%), Ca (2-155%) and Zn (15-259%) compared to the other fertiliser treatments suggesting an additive effect of P fertiliser and rhizobium inoculation. Moreover, the effect of fertiliser treatments was more pronounced in the clay than the sandy soil. Our investigation is the first to document the effects of fertiliser treatment, genotype, and soil type on the accumulation of rhizosphere nutrients in field-grown chickpea. However, we propose further studies, incorporating more cultivars and environments, before making practical recommendations. [ABSTRACT FROM AUTHOR]

The selectivity and efficacy of protoporphyrinogen oxidase (PROTOX) inhibitor herbicides in cassava varieties depend on product formulation, dosage, and soil texture. The aim of this study was to assess the selectivity and efficacy of flumioxazin and sulfentrazone in the cassava variety 'IPR B36' and the clone 'VN 117'. Two experiments were carried out: one in a clayey soil and one in a sandy soil. Both experiments were laid in a split-plot randomized block design with three replicates. The two cassava varieties were used as main plots, with subplots consisting in 10 treatments including, flumioxazin at 50, 75, 100, and 125 g ha-1; sulfentrazone at 250, 500, 750, and 1000 g ha-1; one weed-free control, and one unweeded control. Flumioxazin (=75 g ha-1) and sulfentrazone (=250 g ha-1) achieved mean weed control rates > 70 and 90% in both types of soil for up to 90 days after application. Flumioxazin exhibited fewer residual effects on the cassava varieties than sulfentrazone, particularly in clayey soil. Flumioxazin was selective to the different cassava varieties planted in both soil types, whereas sulfentrazone was more selective in clayey soil. PROTOX inhibitors were effective in controlling weed growth in cassava plots, and there were no varietal differences in herbicide selectivity; however, the use of sulfentrazone should be restricted to maximum spray rates of 250 g ha-1 in sandy soils. [ABSTRACT FROM AUTHOR]

Mat foundations are most typically used in locations featuring weak soils such as soft clays and silts, particularly when building in demanding geotechnical conditions. Because of their poor engineering characteristics and significant difficulties associated with workability, these soils are often removed or avoided by excavating down to a specific depth. However, if thick layers are present, their removal becomes unpractical, costly, and creates inconvenience during construction. To overcome this issue, various reinforcement strategies can be adopted. In this study, the use of stone columns under mat foundations was investigated via numerical modeling. Two scenarios were compared: one in which stone columns were installed without any soil removal and another in which a layer of soft ground was removed and the foundation was installed without any ground treatment. Numerical results showed the clear beneficial effect of stone columns, which can significantly reduce settlements even in the presence of a thick deformable soil layer. [ABSTRACT FROM AUTHOR]

The influence of the geneses of disturbed soils on their mechanical characteristics and their changes with moisture content and compaction degree was studied on the basis of tests of technogenic ash and slag mixtures, sandy soils and clays. It was found that in terms of grain composition, strength and deformation characteristics, ash and slag mixtures occupy an intermediate position between sandy and clay soils but demonstrate several specific features, particularly concerning the influence of the water content on the angle of internal friction. [ABSTRACT FROM AUTHOR]

Processes of soil restoration in anthropogenically disturbed soils is an urgent topic in modern ecology and nature management. Being mediator between mineral soil composition and plant vegetation, soil microbial community is important factor of soil restoration processes. Analysis of main soil nutrition components followed by 16S amplicon sequencing are sufficient methods for primary analysis of novel locations. Here is the primary analysis in a novel location in Northwest Europe (Russia). Main nutrition parameters (pH, P, Na and NH4+) and 16S rDNA Illumina amplicons were explored in abandoned soils from sandy pit quarry (2 sites) and refractory clay mining dumps (4 sites). Microbial communities of mature soils and dumps are variable and different in terms both nutritional and microbial components. pH, N and TOC are strong predictors for microbial composition. Dumps of refractory clays pQ_2 are non-developed soils, highly acidic and form specific microbial community. Differences between dumps and mature soils in both pre-quaternary and quaternary soils are connected with specific bacterial taxa. Those taxa are connected more with plant composition, not the soil properties themselves. The exact changes in microbial community are unique for different soils and areas. [ABSTRACT FROM AUTHOR]

Images from unmanned aerial vehicles (UAV) can serve as a baseline for studies in weed science, complementing observations obtained in the ground. The objective of this work was to determine soybean (Glycine max (L.) Merr.) plant injury caused by pre-emergence herbicides in sandy and clayey soils, using a low-cost UAV. The experiment was conducted in a randomized complete block design, with four replicates and seven treatments consisted of herbicides (diclosulam, chlorimuron, sulfentrazone, flumioxazin, and S-metolachlor), hand weeded and untreated treatments. Ground-based evaluations were carried out to assess soybean crop injury, plant stand, leaf chlorophyll content, plant height, canopy distance and grain yield. Images were taken using a UAV equipped with an RGB (red green and blue) camera. Soybean plants sprayed with diclosulam had lower plant reflectance in the R (98.9), G (147.1) and B (74.3) range than the other treatments in sandy soil. In clayey soil, hand weeded treatment had higher plants (30.8 cm) and untreated favored smaller plants (24.9 cm) compared to herbicide treatments. In sandy soil, soybean yield of all treatments was similar, however in clayey soil, soybean yield treated with chlorimuron and flumioxazin was higher than 5000 kg ha-1 and better than the others treatments. The nutrient-poor soil (sandy) may have aggravated the plant injury caused by herbicides and explain the lower yield observed compared to clayey soil. It was determined soybean plant injury caused by pre-emergence herbicides with the use of unmanned aerial vehicles, providing complementary results to ground-based measurements, indicating the potential of this technology for low-cost evaluations in weed science. [ABSTRACT FROM AUTHOR]

A series of large scale direct shear tests was performed to obtain the shear strength interface parameters for five different geosynthetic reinforcement materials in marginal clayey sandy soil. The performance of geosynthetic layers was evaluated at soil optimum moisture content (OMC) and high moisture content (OMC+6%) conditions. It was observed that the shear strength interface parameters dramatically decreased at 6% wet of optimum in comparison with optimum moisture content. Moreover, a comparison was made between the performance of different geosynthetic layers in a quantitative manner at target moisture content (i.e., OMC+6%). Based on the analysis of large scale direct shear test results, it was concluded that the geosynthetic layer, provided it has high drainage capability, could effectively increase the interface shear strength parameters at OMC+6% condition. [ABSTRACT FROM AUTHOR]

【Objective】 This paper aimed to explore effects of reduced chemical fertilizer and soil texture on yield, quality and nitrogen（N）, phosphorus（P） and potassium（K） fertilizer utilization rate of flue-cured tobacco. 【Method】 Using flue-cured tobacco variety K326 as material, a field experiment was established in sandy soil, clay soil and heavy loam in Qujing tobacco production site, and six fertilization treatments were set up, i.e., T1（CK）（conventional dosage of N, P, K）, T2 and T3（deduced fertilizer N, P, K proportion by 10% and 20%, respectively）, T4 and T5（organic fertilizer replacing 10% and 20% chemical fertilizer, respectively） and T6（no manure or fertilizer）. 【Result】Compared with treatment T1（CK）, treatments T2, T3 significantly improved grade, yield, economical output and N, P, K use efficiency of tobacco leaves in sandy soil. Meanwhile, treatments T2, T3 increased contents of potassium, decreased total sugar, reducing sugar. The contents of total nitrogen, nicotine and water-soluble chloride in the middle and upper parts of leaves were not significantly affected; and the chemical composition was more balanced under T2 and T3. Compared with treatment T1（CK）, treatment T2 and T5 did not significantly improved growth of the tobacco plants in clay soil, but the proportion, yield, output and N, P, K use efficiency under T2 and T5 in tobacco leaves were significantly higher than that of T1（CK）, and the chemical composition of middle and upper position leaves was more balanced. Compared with T1（CK）, treatments T2, T3, T5 had no effect on tobacco plant growth in heavy loam, but improved the proportion of products, yield, output, N, P, K use efficiency of tobacco. Furthermore, the contents of total sugar, reducing sugar of middle and upper part leaves were increased under T2, T3 and T5. The total nitrogen, nicotine, potassium and water-soluble chloride were not affected by treatments. And treatments T2, T3 significantly improved the balance of chemical composition of tobacco leaves. Under the same N, P and K application rate, the N and P uptake and use of tobacco plants in different soils could be sorted as the following: Sandy soil>heavy loam>clay soil, and K use efficiency as the following: Heavy loam>clay soil>sandy soil. 【Conclusion】Based on the current N, P and K usage of tobacco in farmlands, the potential N, P and K proportion of chemical fertilizer reduction（CR） or replacement with organic fertilizer（ROR） in sandy soil was 10%. The N, P and K proportion of CR or ROR in clay soil was 10%-20%. The potential reduction of N, P and K fertilizer in heavy loam was 10%, and the potential proportion ROR was 10%-20%. [ABSTRACT FROM AUTHOR]

The effects of irrigation on winter wheat yield and water use efficiency (WUE) were mostly explored based on site-based experiments in North China Plain (NCP) region. However, due to the influences of contrasting environmental factors (e.g. climate and soil properties), these results cannot be accurately cross-compared among different studies, resulting in the difficulty to get the generalizable pattern at regional scale. Here meta-analysis was conducted to comprehensively evaluate the effects of irrigation on winter wheat yield and WUE in NCP region, with the observation data of 1876 pairs from 186 field experimental papers totally. The differences of the irrigation effects in different regions, precipitation year types, soil texture, and nitrogen (N) application levels were explored, and the corresponding optimal irrigation amounts for reaching high yield and WUE were ascertained. Results showed that compared with non-irrigation during the winter wheat growing period, irrigation increased the yield of winter wheat in NCP by 32.0%-38.3%, and reduced the WUE by 27.1%-30.1%. The yield increment due to irrigation in the northwest of NCP (39.6%-53.5%) with total precipitation during the winter wheat growing period below 150mm was higher than that in the southeast of NCP (24.3%-27.1%) with total precipitation during the winter wheat growing period higher than 150mm, while the decrease of WUE due to irrigation in northwest of NCP (32.4%-37.5%) was higher than that in the southeast of NCP (22.0%-24.3%). The optimum irrigation amount for high yield and WUE of winter wheat was 150-180mm in the northwest and 120-150mm in the southeast. Specifically, for different precipitation year types, the optimum irrigation amounts were 120-150mm with 2 times during jointing and flowering stages for dry year, during jointing and heading stages for normal year, and during jointing and booting stages for wet year. For different soil texture, irrigation under loamy soil had the highest increases in yield, while clay soil had the lowest decreases in WUE; the optimum irrigation amounts of winter wheat with four different soil texture of sandy soil, loam, clay loam and clay were 60-90mm, 120-150mm, 180-210mm, and 150-180mm, respectively. For different N application levels, N application of 120-240kg.ha-1 led to the highest yield and WUE under the irrigation amounts of 80-140mm, of which the higher yield was obtained under irrigation amounts of 110-140mm, and the higher WUE was obtained under the irrigation amounts of 80-110mm. Collectively, the NCP region can achieve the goals of high yield and WUE when irrigation amount was 120-150mm with 2 times but at different stages during different precipitation year types (i.e. dry year, normal year and wet year). Meanwhile, the combination of loam conditions with the N application of 120-240kg.ha-1 can synergistically improve the yield and water use efficiency of winter wheat. [ABSTRACT FROM AUTHOR]

• Long-term expansion rates of 46 Urban Gullies in Kinshasa and Bukavu are quantified. • Gully widening is responsible for most of the gully expansion. • Expansion rates in sandy soils are mainly controlled by land cover and road density. • Expansion rates in clayey soils appear influenced by landslide dynamics. Urban gullies (UGs) are a growing concern in many tropical cities of the Global South. Addressing this new geo-hydrological hazard requires good insights into the rates and controlling factors of this process. Therefore, we investigate the expansion rates of a representative sample of UGs in Kinshasa (n = 17) and Bukavu (n = 29), two contrasting cities in D.R. Congo. We reconstruct long-term (10–17 years) expansion rates, making a distinction between headcut retreat and sidewall widening, and analyse the environmental factors potentially explaining these rates. Total expansion rates varying between 12.6 and 863 m2y-1. Most of this expansion happens through sidewall widening. In Kinshasa, which is mainly characterized by sandy soils, contrasts in expansion rates are mainly correlated to the characteristics of the upslope drainage area of the gullies. Especially the road density and a hypothetical runoff index (combining drainage area, land use and soil characteristics) explain a significant part of the observed variation. In Bukavu, such trends are less apparent. This is likely because the clayey nature of the soils provides more resistance against gullying, resulting in overall smaller and less actives UGs. Furthermore, the already low infiltration rates of these soils probably make the relative impact of urbanization on runoff production smaller. Our results also indicate that UGs located in recent landslides have higher gully expansion rates. The mechanisms behind remain poorly understood. Overall, our work opens promising perspectives to model and predict gully expansion rates in urban settings but may also guide efforts aiming to stabilize UGs. [ABSTRACT FROM AUTHOR]

Eutrophication has led to the widespread occurrence of cyanobacterial blooms. Toxic cyanobacterial blooms with high concentrations of microcystins (MCs) have been identified in the Lalla Takerkoust reservoir in Morocco. The objective of this study was to evaluate the efficiency of the Multi-Soil-Layering (MSL) ecotechnology in removing natural cyanobacterial blooms from the lake. Two MSL pilots were used in rectangular glass tanks (60 × 10 × 70 cm). They consisted of permeable layers (PLs) made of pozzolan and a soil mixture layer (SML) containing local soil, ferrous metal, charcoal and sawdust. The main difference between the two systems was the type of local soil used: sandy soil for MSL1 and clayey soil for MSL2. Both MSL pilots effectively reduced cyanobacterial cell concentrations in the treated water to very low levels (0.09 and 0.001 cells/mL). MSL1 showed a gradual improvement in MC removal from 52 % to 99 %, while MSL2 started higher at 90 % but dropped to 54% before reaching 86%. Both MSL systems significantly reduced organic matter levels (97.2 % for MSL1 and 95.8 % for MSL2). Both MSLs were shown to be effective in removing cyanobacteria, MCs, and organic matter with comparable performance. [Display omitted] • Cyanobacterial cell removal by Multi-Soil-Layering (MSL) ranged from 99 % to 100 % • Greater degradation capacity of MC-LR in MSL1 (sandy soil) and MSL2 (clay soil) • MC-YR variant was most persistent in substrate of both MSL systems • qPCR detected degrading bacteria in both MSL systems • MSL1 had significant abundance of mlrA gene copies and degrading bacteria [ABSTRACT FROM AUTHOR]

The European bioeconomy is steadily driving an industrial, economic, and social growth looking for sustainable biobased feedstocks able to replace fossil-based materials. In this scenario, there is an urgent and increasing need to produce locally industrial crops, with multiple applications and broad suitability to different pedo-climates. Furthermore, the actual EU legislation imposes to produce industrial crops not competing with food ones, and one possibility is to grow them on marginal land. Among others, camelina [ Camelina sativa (L.) Crantz] has been identified as one of the most suitable options for marginal land in Europe, but so far there is a lack of studies conducted in such conditions able to provide reliable production data, on which it will be possible to build plausible business plans. At this scope different field trials have been established in four European countries, i.e., Italy, Greece, Germany, and Poland, in multiple growing seasons from 2018 to 2021, under different types of marginality. In details, in Italy camelina was tested under steep slopes (25% and 15%), in Greece in a soil with low fertility (pH < 5.5) and adverse terrain conditions (steep slope >12%); in Germany in a soil with limitations in rooting, i.e., rooting depth < 30 cm + stoniness > 15%, and in Poland in two sites one with sand > 40%, and the other with clay > 50% of the texture. Camelina was grown with an autumn cycle in Italy and Greece, and with a spring one in Germany and Poland. Camelina production was impacted by the marginal land, seed yield was on average 0.94 Mg DM ha−1, ranging from 0.38 Mg DM ha−1 for camelina sown in spring in Poland in the sandy soil, up to 1.93 Mg DM ha−1 for camelina sown in autumn in Italy on a 15% slope. Camelina completely failed only in one growing season in the clay soil in Poland, in relation to extreme weed pressure, while in all the other situations it was able to produce seed. Seed quality, that was surveyed only in Italy and Poland, was not negatively impacted by marginality, demonstrating its capacity to cope with harsh growing conditions. Growing camelina in southern European marginal land, in autumn sowing, seemed the most conservative and safe strategy to achieve profitable yields. In terms of agronomic management, the most important choices to optimize the crop in marginal land resulted: weed management, N fertilization, and the harvesting phase. • Camelina confirmed to be adapt to European marginal land. • Under marginal land camelina seed yield ranged between 0.38 and 1.93 Mg DM ha-1. • Seed oil content and 1000-seed weight were not negatively impacted by marginality. • Growing camelina in southern European marginal land was the most conservative and safe strategy to achieve profitable yields. [ABSTRACT FROM AUTHOR]

Owing to their specific sedimentary or weathering formation history, most soils confronted in civil engineering can be categorised into clayey and sandy soils. In view of the great mechanical difference, particularly the distinct liquefaction resistance, then precisely simulate the mechanical and liquefaction characteristics of different type soils become an important research issue in seismic design of civil engineering structures. Considering soil turns into overconsolidated state once experiences stress unloading, and which affects the mechanical and liquefaction characteristics in turn. Based on the classical Cam-clay model, with the introducing of subloading surface concept, the subloading surface Cam-clay model provide an unified constitutive model in the numerical simulation of different type soils. Based on the comprehensive parametric studies of state variables evolution and anti-liquefaction capability of soil conducted in this paper, we creatively unified the relationship between OCR and relative density of soil that widely adopted in the liquefaction resistance evaluation of sandy soil, and our test results shows high correlation between these two parameters. These findings provide a solid theoretic support and guidance for the dynamic compaction method that widely adopted in anti-liquefaction design. [ABSTRACT FROM AUTHOR]

The liquefaction phenomenon may originate in fine sandy - silty type of soils subjected to dynamic effects, low plasticity clays and even in soils with gravels based on the magnitude of applied acceleration. The mechanical or chemical soil improvement techniques have been used to prevent this problem. The mixing or grouting operations of sodium polyacrylate, which has a high-water absorption capacity, is one of the chemical soil improvement techniques. The frost behavior of this material, which turns into a gel form when react with the water in the environment, is not known in the permafrost areas. Within this purpose, sandy specimens including 5.00%, 10.00%, 15.00%, and 20.00% sodium polyacrylate gel as well as reference ones, were frozen at -20C° and unconfined compression tests were applied. Moreover, the tests were repeated for additional specimens containing 5.00% bentonite clay by weight. Although the unconfined compressive strength of all samples improved according to the increase in the amount of water with the gel content, about 14.00% lower values were obtained in specimens containing bentonite. On the other hand, the unit strain values of frozen samples without bentonite increased, while reduction observed in samples with bentonite. The viscous structure, that is in gel form inside the soil, dissipates volume increase during the freezing process and prevents the frost heave problem. However, the loss of bearing capacity should be considered in case of insufficient saturation in liquefaction sensitive sandy soils improved with sodium polyacrylate. [ABSTRACT FROM AUTHOR]

Deinking paper sludge (DPS) soil amendments have potential as a climate change mitigation strategy. Understanding how DPS application affects carbon mineralization in different soil textures is crucial but has not been well investigated. We performed a 120 days incubation experiment to evaluate the effect of soil texture and DPS amount on CO2 emissions. Three different textures were tested: silty clay, sandy-silt and sandy with three DPS doses: 0, 30 and 60 t.ha-1. Results showed that DPS mineralization without soil seemed very rapid with a high mineralized carbon amount (more than 2.500 gC.kg-1DPS), but did not reach the stable phase. For amended soils, soil texture effects are marked at the end of incubation. The cumulative carbon mineralization depended significantly on soil texture and DPS doses with a significant interaction. Among all soils with different dose application, the highest cumulative carbon mineralization was revealed for silty-clay soil by applying 30 t.ha-1 as well as 60 t.ha-1 of DPS. However, the lowest values occurred for sandy soil. Only this latter achieved the stabilization phase after 120 days and therefore stopped CO2 emission. The highest potential mineralization rate (C0) was achieved for silty-clay soil by applying the two DPS doses. The mineralization rate (C0*k) was two times higher for this soil than the sandy soil. The kinetic deviation of carbon mineralization applying the highest DPS doses (60 t.ha-1) is similar for the four studied soils because of C-decomposition blockage. These findings highlight the necessity to consider the combined effects of the DPS amount and soil texture for assessing C release in DPS-amended soils. [ABSTRACT FROM AUTHOR]

There are growing evidence that nitrogen (N) recommendation based on the expected yield concept developed by Stanford in 1973 lacks in agronomic principles, despite it widespread use worldwide. In Brazil, the main sugarcane producer worldwide, for example, a fixed N factor of 1 kg N per Mg−1 of stalk is used. However, literature demonstrates that sugarcane responsiveness to N is much higher in sandy soils rather than in clayey soils, whereas the recommended N is usually higher in clayey soils because of its improved yield potential. We investigated 146 response curves of sugarcane (Saccharum spp.) to N to define a better approach for determining N rates instead of using exclusively the expected yield concept. First, we found no correlation between the economically optimal N rate (Nopt, kg ha−1) and the yield (Mg ha−1) obtained in Nopt. Second, we calculate the N requirement (Nreq, kg N Mg−1 stalk) as the quotient between Nopt and the yield, for each response curve. There was a negative correlation between yield at control plot and Nreq, demonstrating that higher N rates are required to maximize yield in sandy (low yield) sites. The Nreq was 1.3, 0.9, 0.7 and 0.6 kg N Mg−1 stalk for expected yields < 69, 69–84, 84–102, and > 102 Mg ha−1, respectively, differing from the standard 1 kg N Mg−1 stalk currently used. The method proposed here is based indirectly on the N-supplying power of the soil and should be tested for other crops to deliver an improved N recommendation system. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of coral reef sandy soil is significantly different from the sand and clay soils. Currently, Terzaghi's bearing capacity equation is still commonly applied to evaluate the bearing capacity of coral reef, while the calculation result is not consistent with the actual condition. Based on a port project in east Africa, plate loading test of the coral reef sandy soil has been conducted and the P-S curves are obtained, and the bearing capacity values obtained from the plate loading test results are compared with the calculated results based on the Terzaghi's bearing capacity equation. According to multiple linear regression and the optimal regression equation selected by the significance test, the modified Terzaghi foundation equation of bearing capacity in coral reef sandy soil area is proposed, and the modified Terzaghi foundation equation has important reference value for the calculating of the bearing capacity of the coral reef sandy soil foundations. [ABSTRACT FROM AUTHOR]

In this letter, the authors propose a microwave sensor capable to detect soil moisture content parameter for use in precision agriculture and agricultural smart monitoring applications. The novel sensor is based on complementary split‐ring resonator metamaterial topology, microstrip line and was built under biodegradable dielectric substrate of polylactic acid for sustainable purposes. The sensing mechanism relates the sensor's resonant frequency to the soil moisture content changes over time. For experimental validation purposes, a compact sensor prototype (75 mm × 35 mm × 1.55 mm and 12 g) with fundamental resonant frequency at 958 MHz was built and submitted to calibration process on typically sandy and clay soils to get fitting models capable to estimate soil moisture content. Simulated and experimental results are presented together and show good agreement with each other. The calibration data for both soil types were processed using the least‐squares method and the proposed curve‐fitting models are capable to estimate soil moisture content levels from 5% to 20% for sandy soil and from 12% to 23% for clay soil with satisfactory accuracy, proving the device viability. [ABSTRACT FROM AUTHOR]