The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics ...The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.展开更多
Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of th...Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of the areas of the City of Diwaniyah,in a house covered with green netting,with a shade rate of 25%,to study the effect of bentonite and humic acid on the growth and flowering of a Catharanthus roseus L.plant in sandy soil.The experiment included two factors:the first factor was bentonite clay,and the second factor was humic acid.Using a randomized complete block design(R.C.B.D)with three replications,data were analyzed using the analysis of variance(ANOVA)method,and comparison was made according to the least significant difference(L.S.D)test at a probability level of 0.05.The experiment consisted of adding bentonite clay at 0,2,6,and 8 g L-1,humic acid at 0,0.5,1,and 10 g L-1.The results showed that adding bentonite clay and humic acid to sandy soil can have a significant positive effect on the growth and flowering of the Catharanthus roseus plant grown in poor sandy soil conditions.Bentonite,clay and humic acid were added at concentrations of 8 and 10 g L-1,which led to an increase in plant height and number of leaves and leaf area.They reached 30.07,23.84 cm2,76.62,63.42 cm2 for leaf-1 and 24.73,20.22 cm2 for leaf-1,respectively.The results also showed an increase in the content of nitrogen(N),phosphorus(P),and potassium(K)in leaves by 2.27,1.92,1.99%and 1.51,1.22,1.77%.This also led to an increase in chlorophyll pigment and anthocyanin at the highest concentration and gave the highest value.Therefore,adding bentonite and humic acid together gave the highest values in vegetative and chemical characteristics,compared to treatments without addition.展开更多
The soil packing,influenced by variations in grain size and the gradation pattern within the soil matrix,plays a crucial role in constituting the mechanical properties of sandy soils.However,previous modeling approach...The soil packing,influenced by variations in grain size and the gradation pattern within the soil matrix,plays a crucial role in constituting the mechanical properties of sandy soils.However,previous modeling approaches have overlooked incorporating the full range of representative parameters to accurately predict the soaked California bearing ratio(CBR_(s))of sandy soils by precisely articulating soil packing in the modeling framework.This study presents an innovative artificial intelligence(AI)-based approach for modeling the CBR_(s)of sandy soils,considering grain size variability meticulously.By synthesizing extensive data from multiple sources,i.e.extensive tailored testing program undertaking multiple tests and extant literature,various modeling techniques including genetic expression programming(GEP),multi-expression programming(MEP),support vector machine(SVM),and multi-linear regression(MLR)are utilized to develop models.The research explores two modeling strategies,namely simplified and composite,with the former incorporating only sieve analysis test parameters,while the latter includes compaction test parameters alongside sieve analysis data.The models'performance is assessed using statistical key performance indicators(KPIs).Results indicate that genetic AI-based algorithms,particularly GEP,outperform SVM and conventional regression techniques,effectively capturing complex relationships between input parameters and CBR_(s).Additionally,the study reveals insights into model performance concerning the number of input parameters,with GEP consistently outperforming other models.External validation and Taylor diagram analysis demonstrate the GEP models'superiority over existing literature models on an independent dataset from the literature.Parametric and sensitivity analyses highlight the intricate relationships between grain sizes and CBR_(s),further emphasizing GEP's efficacy in modeling such complexities.This study contributes to enhancing CBR_(s)modeling accuracy for sandy soils,crucial for pertinent infrastructure design and construction rapidly and cost-effectively.展开更多
Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and respons...Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.展开更多
The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke抏rqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the ...The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke抏rqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the aeolian sandy soil in different ratios. Two-year-old Pinus sylvestris var. mongolica seedlings and plastic pots were used in the experiment. The experimental results indicated that: 1) the peat and weathered coal could significantly improve the physical and chemical prop-erties of aeolian sandy soil, and thus promoted the growth of seedlings; 2) the effect of peat on seedling growth, including height, base diameter, root length and biomass, presented an order of 8%>10%>5%>2%>0 in terms of peat contents, and the effect of weathered coal on seedling growth presented an order of 5%>8%>10%>2%>0 in terms of weathered coal contents for height and basal diameter, 5%>8%>2% >10%>0 for root length, and 5%>2%>8% >10%>0 for biomass; 3) the effects of peat were generally greater than that of weathered coal. Meanwhile, 8% peat was the best treatment to promote the growth of P. sylvestris var. mongolica seedlings.展开更多
[Objective] This research aimed to explore the existing forms of ammonium nitrogen adsorbed in a sandy soil with different particle sizes by extraction experiments and provide references for investigating the transpor...[Objective] This research aimed to explore the existing forms of ammonium nitrogen adsorbed in a sandy soil with different particle sizes by extraction experiments and provide references for investigating the transport and transformation of the ammonium in the vadose zone.[Method] Sandy soil sample was collected from a landfill and sieved into coarse sand and fine sand.The three kinds of samples were soaked in NH4Cl solution with different initial concentrations,respectively.Then,ammonium adsorbed in soil samples were extracted by three kinds of extraction agents with different extraction capacity,including water,KCl and CaCl2.[Result] The order of extraction capacity of different extraction agents was：water KCl CaCl2;when the concentration of ammonium was low in solution,the ammonium preferentially adsorbed in the exchangeable positions of minerals and mainly existed in the form of exchangeable ammonium;with the increase of concentration,ammonium entered inside the 2：1 clay minerals with enough driving force of the concentration differences and existed in the form of fixed ammonium;little fixed ammonium was observed in coarse sand samples,which was mainly existed in 2：1 clay minerals with strong extraction capacity.[Conclusion] The existing forms of ammonium were closely related to the mineral compositions in soil and the initial concentrations of ammonium.展开更多
The soil factors influencing the potential migration of dissolved and particulate phosphorus(P) from structurally-weak sandy subsoils were evaluated by means of soil column leaching experiments. Soil colloids were ext...The soil factors influencing the potential migration of dissolved and particulate phosphorus(P) from structurally-weak sandy subsoils were evaluated by means of soil column leaching experiments. Soil colloids were extracted from two types of soils to make the colloid-bound forms of P solution. Eight sandy soils with diverse properties were collected for packing soil columns. The effects of influent solutions varying in concentrations of colloids,P,and electrolyte,on the transport of P and quality of leachates were characterized. P migration in the soils was soil property-dependent. High soil electrical conductivity values retarded the mobility of colloids and transportability of colloid-associated P(particulate P) . Soil electrical conductivity was negatively correlated with colloids and reactive particulate P(RPP) concentrations in the leachates,whereas,the total reactive P(TRP) and dissolved reactive P(DRP) concentrations in the leachates were mainly controlled by the P adsorption capacity and the P levels in the subsoil. The reactive particulate P in the leachates was positively correlated with the colloidal concentration. Increased colloidal concentration in the influent could significantly increase the colloidal concentration in the leachates. Elevated P concentration in the influent had little effect on P recovery in the leachates,but it resulted in significant increases in the absolute P concentration in the leachates.展开更多
Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas.The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate p...Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas.The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate precipitation(SICP)on reducing wind erosion risk of sandy soil.Field tests were carried out in Ulan Buh Desert,Ningxia Hui Autonomous Region,China.Results showed that the SICP method could significantly enhance the surface strength and wind erosion resistance of the topsoil.The optimal cementation solution(urea-CaCl2)concentration and spraying volume,according to experiments conducted on sandy land,were 0.2 mol/L and 4 L/m^2,respectively.Under this condition,the CaCO3 content was approximately 0.45%,the surface strength of sandy soil could reach 306.2 kPa,and the depth of wind erosion was approximately zero,after 30 d completion of SICP treatment.Soil surface strength declined with the increase of time,and long-term sand fixation effects of SICP treatment varied depending on topography.Whereas wind erosion in the top area of the windward slope was remarkable,sandy soils on the bottom area of the windward slope still maintained a relatively high level of surface strength and a low degree of wind erosion 12 month after SICP treatment.Scanning electron microscopy(SEM)tests with energy dispersive X-ray(EDX)confirmed the precipitation of CaCO3 and its bridge effect.These findings suggested that the SICP method is a promising candidate to protect sandy soil from wind erosion in desert areas.展开更多
A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effec...A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown. The effect of B-HA, added at 30 Mg ha^(-1), was studied at 1,3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China. The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil. Amending the sandy soil with B-HA also increased the content of microbial biomass(MB)-carbon,-nitrogen and-phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase. The significant effect of maize(Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively. In comparison, B-HA accounted for 8% of the total variability for each of the same two variables. B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas. The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.展开更多
Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of...Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the south- eastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that： （1） The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest： in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. （2） Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. （3） The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. （4） The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.展开更多
This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy s...This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy soil, was studied using batch experiments, es-pecially for effects of reaction time, pH, concentrations, temperature and irradiation on the reduction of Cr (VI), and the optimum reaction conditions. The results indicated a significant increase of the adsorption of Cr (VI) because of the complexion reaction between HA and Cr (VI) that occurred under acidic condition. The reaction mechanisms of HA with chromium on sand surfaces were certified. Thus it came to a conclusion that HA could be used effectively on remediation of Cr (VI)–contaminated soil and groundwater in a wide range of pH, with or without sunlight. These results suggest that the organic-inorganic complex—such as sandy soils coated with humic substances—is important as a metal reservoir in the environment.展开更多
We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties....We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil.展开更多
To assess the effects of savanna afforestation on soil phosphorus （P） transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons （0-5 cm a...To assess the effects of savanna afforestation on soil phosphorus （P） transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons （0-5 cm and 5-20 cm） under a savanna and an adjacent 30-year-old Mongolian pine （Pinus sylvestris L. vat. mongolica Litv.） plantation on a P-deficient semi arid sandy soil. The results showed that all soil P fractions and phosphomonoestcrase activities decreased with soil depth at both sites except that labile organic P under the plantation was constant with soil depth, In contrast to savanna, soils trader Mongolian pine plantation had lower phosphomonoesterase activities and concentrations of all P fractions （with an exception of Al-P）, lower proportions of organic P and Ca-P in total P, and higher proportions of labile P, Al-P and Fe-P in total P. These results suggested that P transformations mainly occurred in surface soils, and P recycled through litterfall was the most important source of plant available P. Mongolian pine afforestation enhanced the bioavailability of both organic P and Ca-P. simultaneously reduced soil P pools. indicating that protection of forest floor and P fertilization are necessary to maintain the sustainable functioning of Mongolian pine plantations.展开更多
This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccen...This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, （e is the lateral load eccentricity and d is the diameter of pile） of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.展开更多
Afforestation in sandy soils can cause soil acidification and affect Cu and Zn release. The behaviors of Cu and Zn release from contaminated arable sandy soils were investigated in the laboratory with the methods of s...Afforestation in sandy soils can cause soil acidification and affect Cu and Zn release. The behaviors of Cu and Zn release from contaminated arable sandy soils were investigated in the laboratory with the methods of simulated acidification of the soils. The results showed that soil acidification could change chemical forms of Cu and Zn in the soils, impel the transformation of Cu and Zn from carbonate associated fractions to exchangeable, organic matter and oxides associated fractions, and thus increase the release potential of Cu and Zn in the soils. The effect of the acidification on Zn leaching was more significant than that of Cu. Water solubility of Cu and Zn in the soils was increased with decreasing pH, and the solubility of Cu and Zn was increased exponentially at pH 3.8-4.5, and 6.2-6.5, respectively.展开更多
The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentra...The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentrations were collected for evaluating the relationships between Cu and Zn release and extraction time, ratio of soil to water, pH and electrolyte types. The results indicated that Cu released in batch extraction that represents long-term leaching was mainly from exchangeable, and carbonate bound Cu fractions, and Zn released in the batch extraction was mainly from its carbonate bound fraction. However, the Cu and Zn leached from the soils using the column leaching that represents short-term leaching were mainly from their exchangeable fractions. Soil column leaching at different pH values indicated that the amounts of leached Zn and Cu were greatly affected by pH. The Cu and Zn release experiments with varying extraction times and ratio of soil to water suggest that long-term water-logging in the soils after rain may increase contact time of the soils with water and the release of Cu and Zn to water from the soils, and total amounts of Cu or Zn released from the soils increase, but the Cu or Zn concentration in the surface runoff decrease with increasing rainfall intensity. The increased Ca concentration in soil solution increased stability of organic matter-mineral complexes and might decrease the dissolution of organic matter, and thus decreased the release of Cu-binding component of organic matter. However, high concentration of Na in the soil solution increased the dispersion of the organic matter-mineral complexes and increased dissolution of organic matter and the release of Cu from the soils.展开更多
The property of hydrophilic polymers capable absorbing huge volumes of water led to many practical applications of these new materials in arid regions for improving the water retention in sandy soils. Effects of four ...The property of hydrophilic polymers capable absorbing huge volumes of water led to many practical applications of these new materials in arid regions for improving the water retention in sandy soils. Effects of four carboxymethylcelluloses （CMC） mixed at various rates with the sandy soil, on the water-holding capacity and hydraulic conductivity （Ks） when leached with distilled water （simulating rain）, tap water, and saline water were evaluated. The maximum water absorption of CMCs ranged between 80 and 100 kg. kg^-1 of polymer; however, the absorbent swelling capacity decreased significantly with increasing the salt concentration in the solution. The water absorption capacity of CMCs decreased significantly when incorporated in the sandy soil compared to that of the absorbent alone. Application of CMC increased significantly the available water content up to 3 ± 0.5 times. All soils treated with CMCs showed a significant lower in Ks compared to the control soil. Meanwhile, Ks was found increased with increasing the salt concentration in the leaching solution. This understanding of characteristics of the absorbents and the interactions among absorbents, soil, and irrigation water quality would be of help in water management of sandy soil展开更多
With the aim to apply the beneficial microorganisms to peanut （groundnut （Arachis hypogaea）） growing in sandy soil of Binhdinh province in Vietnam, the paper was conducted to study the isolation, selection of N-fi...With the aim to apply the beneficial microorganisms to peanut （groundnut （Arachis hypogaea）） growing in sandy soil of Binhdinh province in Vietnam, the paper was conducted to study the isolation, selection of N-fixing, phosphate, potassium solubilizing and slime producing microorganism from sandy soil and peanut root samples, and evaluate the capability of selected isolates to adapt to the sandy soil condition. The isolation and selection of beneficial microbes were based on the biological activity of isolates, which was determined by acetylene reduction assay and nodulation on the peanut for Rhizobium spp., by testing the capability to solubilize Ca3（PO4）2 or fenspat in the growth medium for phosphate, potassium solubilizing microbes, and by measurement of the viscosity of Hansen medium for slime producing microorganism. All isolates were evaluated for the effectiveness on the nutrition uptake and growth of peanut by carrying out at the greenhouse and field experiments. To evaluate the adaptation of selected isolates to the sandy soil condition, the experiments were carried out in the laboratory to determine the microbial density in suitable medium, containing different NaCI concentrations or with different pH or at different temperatures. The results showed that rhizobial strain RA18 had an N-fixing activity value of 3,458 ＋ 10.95 nmol C2H2/plant and can supply 30% of N required for peanut. The bacterial strain P 1107 is able to solubilize phosphate and can increase phosphorus uptake by 30% in peanut. Further, inoculation of peanut with the bacterial strain S3.1 can save 30% required mineral potassium, and the Lipomyces strain PT5.1 can produce the slime, which can provide the sandy soil to keep moisture for 15 d longer than the control without the inoculation. All selected isolates are able to grow at temperatures from 20 ℃ to 35 ℃, pH from 4.5 to 6.0 and the salinity of 0.2%o-0.6%o NaCI, and can well adapt to the sandy soil conditions.展开更多
In this paper, a study of sandy soil compaction with different granulometry and moisture content has been performed, and soil mechanical property variations in moisture and granulometry have been investigated. Investi...In this paper, a study of sandy soil compaction with different granulometry and moisture content has been performed, and soil mechanical property variations in moisture and granulometry have been investigated. Investigations were performed to compare hydrostatic compression test （HCT） responses and evaluate the compression index, Cc, which is an indicator of the soil＇s susceptibility to compaction-induced damage. The experiments have been performed on 24 soil samples typologies. Each sample has been obtained by combining three types of soil granulometry （types A, B and C） with a relative content varying from 0% to 100% in 20% increments. Soil type A had a granulometry ranging between 0.5 mm and 1 mm, type B between 0.25 mm and 0.5 mm, and type C less than 0.25 mm. These samples were representative of a sandy soil, chemically inactive and had various granulometries and initial moisture contents. A cell for HCT has been set up to allow the initial volume measurement of the test pieces and the subsequent changes during HCT with an estimated error less than 0.1 cm3. All samples were pre-compacted and prepared in agreement with the actual standards. The experimental data are reported in diagrams, the data allowed comparison of the mechanical behaviors between the considered unsaturated soils and underlined how soil moisture and granulometry affect soil response during HCT. Furthermore, because of the methodology used, the equipment was very economical.展开更多
The sandy soils of Mostaganem plateau are vety, poor in clay. They are characterized by very low fertility and water holding capacity. The addition of bentonite to these soils and the cultivation of durum wheat, in co...The sandy soils of Mostaganem plateau are vety, poor in clay. They are characterized by very low fertility and water holding capacity. The addition of bentonite to these soils and the cultivation of durum wheat, in combination with the chickpeas, are two eco-physiological strategies to rehabilitate their agricultural suitability. This study was conducted on two plant species： a local variety of durum wheat （Waha） and a legume, chickpea （variety ILC 3279）, on a substrate bentonite at 10% dose. For each stage of growth measurements of stem height, leaf area and plants vegetative nitrogen content were quantified. Changes in total nitrogen content of durum wheat grown in substrates amended with 10% bentonite or not during the development of durum wheat in monoculture and in association with the chickpeas were analyzed. The results showed that the total nitrogen content of durum wheat was significantly higher at three leaves and tailoring stages, when durum wheat was associated with chickpea in the same soil. However, the results showed no difference during the lifting and two leaves stages. There was also a positive effect of treatment at 10% of bentonite on the plant total nitrogen content regardless of the stage and the culture system.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42372312,and 42172299)the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20220807).
文摘The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.
文摘Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of the areas of the City of Diwaniyah,in a house covered with green netting,with a shade rate of 25%,to study the effect of bentonite and humic acid on the growth and flowering of a Catharanthus roseus L.plant in sandy soil.The experiment included two factors:the first factor was bentonite clay,and the second factor was humic acid.Using a randomized complete block design(R.C.B.D)with three replications,data were analyzed using the analysis of variance(ANOVA)method,and comparison was made according to the least significant difference(L.S.D)test at a probability level of 0.05.The experiment consisted of adding bentonite clay at 0,2,6,and 8 g L-1,humic acid at 0,0.5,1,and 10 g L-1.The results showed that adding bentonite clay and humic acid to sandy soil can have a significant positive effect on the growth and flowering of the Catharanthus roseus plant grown in poor sandy soil conditions.Bentonite,clay and humic acid were added at concentrations of 8 and 10 g L-1,which led to an increase in plant height and number of leaves and leaf area.They reached 30.07,23.84 cm2,76.62,63.42 cm2 for leaf-1 and 24.73,20.22 cm2 for leaf-1,respectively.The results also showed an increase in the content of nitrogen(N),phosphorus(P),and potassium(K)in leaves by 2.27,1.92,1.99%and 1.51,1.22,1.77%.This also led to an increase in chlorophyll pigment and anthocyanin at the highest concentration and gave the highest value.Therefore,adding bentonite and humic acid together gave the highest values in vegetative and chemical characteristics,compared to treatments without addition.
文摘The soil packing,influenced by variations in grain size and the gradation pattern within the soil matrix,plays a crucial role in constituting the mechanical properties of sandy soils.However,previous modeling approaches have overlooked incorporating the full range of representative parameters to accurately predict the soaked California bearing ratio(CBR_(s))of sandy soils by precisely articulating soil packing in the modeling framework.This study presents an innovative artificial intelligence(AI)-based approach for modeling the CBR_(s)of sandy soils,considering grain size variability meticulously.By synthesizing extensive data from multiple sources,i.e.extensive tailored testing program undertaking multiple tests and extant literature,various modeling techniques including genetic expression programming(GEP),multi-expression programming(MEP),support vector machine(SVM),and multi-linear regression(MLR)are utilized to develop models.The research explores two modeling strategies,namely simplified and composite,with the former incorporating only sieve analysis test parameters,while the latter includes compaction test parameters alongside sieve analysis data.The models'performance is assessed using statistical key performance indicators(KPIs).Results indicate that genetic AI-based algorithms,particularly GEP,outperform SVM and conventional regression techniques,effectively capturing complex relationships between input parameters and CBR_(s).Additionally,the study reveals insights into model performance concerning the number of input parameters,with GEP consistently outperforming other models.External validation and Taylor diagram analysis demonstrate the GEP models'superiority over existing literature models on an independent dataset from the literature.Parametric and sensitivity analyses highlight the intricate relationships between grain sizes and CBR_(s),further emphasizing GEP's efficacy in modeling such complexities.This study contributes to enhancing CBR_(s)modeling accuracy for sandy soils,crucial for pertinent infrastructure design and construction rapidly and cost-effectively.
基金National Natural Science Foundation of China under Grant No.52278503。
文摘Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.
基金This research was supported by Key Knowledge Innova-tion Project (SCXZD0102) of Institute of Applied Ecology Chinese Academy of Sciences and sponsored by the Science and Technology Department of Inner Mongolia Autonomic Region,P. R. China (2001010)
文摘The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke抏rqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the aeolian sandy soil in different ratios. Two-year-old Pinus sylvestris var. mongolica seedlings and plastic pots were used in the experiment. The experimental results indicated that: 1) the peat and weathered coal could significantly improve the physical and chemical prop-erties of aeolian sandy soil, and thus promoted the growth of seedlings; 2) the effect of peat on seedling growth, including height, base diameter, root length and biomass, presented an order of 8%>10%>5%>2%>0 in terms of peat contents, and the effect of weathered coal on seedling growth presented an order of 5%>8%>10%>2%>0 in terms of weathered coal contents for height and basal diameter, 5%>8%>2% >10%>0 for root length, and 5%>2%>8% >10%>0 for biomass; 3) the effects of peat were generally greater than that of weathered coal. Meanwhile, 8% peat was the best treatment to promote the growth of P. sylvestris var. mongolica seedlings.
基金Supported by Major Project of Water Pollution Control and Treatment(2009ZX07424-002)~~
文摘[Objective] This research aimed to explore the existing forms of ammonium nitrogen adsorbed in a sandy soil with different particle sizes by extraction experiments and provide references for investigating the transport and transformation of the ammonium in the vadose zone.[Method] Sandy soil sample was collected from a landfill and sieved into coarse sand and fine sand.The three kinds of samples were soaked in NH4Cl solution with different initial concentrations,respectively.Then,ammonium adsorbed in soil samples were extracted by three kinds of extraction agents with different extraction capacity,including water,KCl and CaCl2.[Result] The order of extraction capacity of different extraction agents was：water KCl CaCl2;when the concentration of ammonium was low in solution,the ammonium preferentially adsorbed in the exchangeable positions of minerals and mainly existed in the form of exchangeable ammonium;with the increase of concentration,ammonium entered inside the 2：1 clay minerals with enough driving force of the concentration differences and existed in the form of fixed ammonium;little fixed ammonium was observed in coarse sand samples,which was mainly existed in 2：1 clay minerals with strong extraction capacity.[Conclusion] The existing forms of ammonium were closely related to the mineral compositions in soil and the initial concentrations of ammonium.
基金the Natural Science Foundation of Zhejiang Province, China (No.R306011).
文摘The soil factors influencing the potential migration of dissolved and particulate phosphorus(P) from structurally-weak sandy subsoils were evaluated by means of soil column leaching experiments. Soil colloids were extracted from two types of soils to make the colloid-bound forms of P solution. Eight sandy soils with diverse properties were collected for packing soil columns. The effects of influent solutions varying in concentrations of colloids,P,and electrolyte,on the transport of P and quality of leachates were characterized. P migration in the soils was soil property-dependent. High soil electrical conductivity values retarded the mobility of colloids and transportability of colloid-associated P(particulate P) . Soil electrical conductivity was negatively correlated with colloids and reactive particulate P(RPP) concentrations in the leachates,whereas,the total reactive P(TRP) and dissolved reactive P(DRP) concentrations in the leachates were mainly controlled by the P adsorption capacity and the P levels in the subsoil. The reactive particulate P in the leachates was positively correlated with the colloidal concentration. Increased colloidal concentration in the influent could significantly increase the colloidal concentration in the leachates. Elevated P concentration in the influent had little effect on P recovery in the leachates,but it resulted in significant increases in the absolute P concentration in the leachates.
基金Projects(51978244,51979088,51608169)supported by the National Natural Science Foundation of China。
文摘Wind erosion is a major cause of land desertification and sandstorm formation in arid and semi-arid areas.The objective of this study was to evaluate the potential of soybeans crude extract induced calcium carbonate precipitation(SICP)on reducing wind erosion risk of sandy soil.Field tests were carried out in Ulan Buh Desert,Ningxia Hui Autonomous Region,China.Results showed that the SICP method could significantly enhance the surface strength and wind erosion resistance of the topsoil.The optimal cementation solution(urea-CaCl2)concentration and spraying volume,according to experiments conducted on sandy land,were 0.2 mol/L and 4 L/m^2,respectively.Under this condition,the CaCO3 content was approximately 0.45%,the surface strength of sandy soil could reach 306.2 kPa,and the depth of wind erosion was approximately zero,after 30 d completion of SICP treatment.Soil surface strength declined with the increase of time,and long-term sand fixation effects of SICP treatment varied depending on topography.Whereas wind erosion in the top area of the windward slope was remarkable,sandy soils on the bottom area of the windward slope still maintained a relatively high level of surface strength and a low degree of wind erosion 12 month after SICP treatment.Scanning electron microscopy(SEM)tests with energy dispersive X-ray(EDX)confirmed the precipitation of CaCO3 and its bridge effect.These findings suggested that the SICP method is a promising candidate to protect sandy soil from wind erosion in desert areas.
基金financial support provided by the National Special Fund for Agro-scientific Research in the Public Interest of China(201303126)Agricultural Science and Technology Achievements Transformation Demonstration of Production and Application Technology and Popularization of Sandy Soil Amendment,Inner Mongolia,China(sq2012eca400008)。
文摘A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown. The effect of B-HA, added at 30 Mg ha^(-1), was studied at 1,3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China. The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil. Amending the sandy soil with B-HA also increased the content of microbial biomass(MB)-carbon,-nitrogen and-phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase. The significant effect of maize(Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively. In comparison, B-HA accounted for 8% of the total variability for each of the same two variables. B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas. The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.
基金funded by the National Natural Science Foundation of China (41140028, 41340043)the Central University Research Foundation, Chang'an University (310827152014)the State Key Laboratory of Loess and Quaternary Geology (SKLLQG)
文摘Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the south- eastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that： （1） The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest： in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. （2） Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. （3） The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. （4） The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.
基金supported by the National Key Technologies R&D Program in the 11th Five-year Plan (2004BA901A15)the Key Program of National Natural Science Foundation of China (Grant No. 90702001)
文摘This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy soil, was studied using batch experiments, es-pecially for effects of reaction time, pH, concentrations, temperature and irradiation on the reduction of Cr (VI), and the optimum reaction conditions. The results indicated a significant increase of the adsorption of Cr (VI) because of the complexion reaction between HA and Cr (VI) that occurred under acidic condition. The reaction mechanisms of HA with chromium on sand surfaces were certified. Thus it came to a conclusion that HA could be used effectively on remediation of Cr (VI)–contaminated soil and groundwater in a wide range of pH, with or without sunlight. These results suggest that the organic-inorganic complex—such as sandy soils coated with humic substances—is important as a metal reservoir in the environment.
文摘We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil.
基金This work was supported by Innovation Research Project of Chinese Academy of Sciences （KZCX3-SW-418）, National Natural Science Foundation of China （30471377） and sustentation project of the Institute of Applied Ecology of Chinese Academy of Sciences （SLYQY0409）.
文摘To assess the effects of savanna afforestation on soil phosphorus （P） transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons （0-5 cm and 5-20 cm） under a savanna and an adjacent 30-year-old Mongolian pine （Pinus sylvestris L. vat. mongolica Litv.） plantation on a P-deficient semi arid sandy soil. The results showed that all soil P fractions and phosphomonoestcrase activities decreased with soil depth at both sites except that labile organic P under the plantation was constant with soil depth, In contrast to savanna, soils trader Mongolian pine plantation had lower phosphomonoesterase activities and concentrations of all P fractions （with an exception of Al-P）, lower proportions of organic P and Ca-P in total P, and higher proportions of labile P, Al-P and Fe-P in total P. These results suggested that P transformations mainly occurred in surface soils, and P recycled through litterfall was the most important source of plant available P. Mongolian pine afforestation enhanced the bioavailability of both organic P and Ca-P. simultaneously reduced soil P pools. indicating that protection of forest floor and P fertilization are necessary to maintain the sustainable functioning of Mongolian pine plantations.
基金Thailand Research Fund and Commission on Higher Education,Ministry of Education,Thailand Under Grant No.MRG5180268
文摘This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, （e is the lateral load eccentricity and d is the diameter of pile） of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.
基金This paper was supported by the National Key Basic Research Support Foundation （NKBRSF） of China （No. 2005CB 121104） and the National Natural Science Foundation of China （No. 40471064）.
文摘Afforestation in sandy soils can cause soil acidification and affect Cu and Zn release. The behaviors of Cu and Zn release from contaminated arable sandy soils were investigated in the laboratory with the methods of simulated acidification of the soils. The results showed that soil acidification could change chemical forms of Cu and Zn in the soils, impel the transformation of Cu and Zn from carbonate associated fractions to exchangeable, organic matter and oxides associated fractions, and thus increase the release potential of Cu and Zn in the soils. The effect of the acidification on Zn leaching was more significant than that of Cu. Water solubility of Cu and Zn in the soils was increased with decreasing pH, and the solubility of Cu and Zn was increased exponentially at pH 3.8-4.5, and 6.2-6.5, respectively.
文摘The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentrations were collected for evaluating the relationships between Cu and Zn release and extraction time, ratio of soil to water, pH and electrolyte types. The results indicated that Cu released in batch extraction that represents long-term leaching was mainly from exchangeable, and carbonate bound Cu fractions, and Zn released in the batch extraction was mainly from its carbonate bound fraction. However, the Cu and Zn leached from the soils using the column leaching that represents short-term leaching were mainly from their exchangeable fractions. Soil column leaching at different pH values indicated that the amounts of leached Zn and Cu were greatly affected by pH. The Cu and Zn release experiments with varying extraction times and ratio of soil to water suggest that long-term water-logging in the soils after rain may increase contact time of the soils with water and the release of Cu and Zn to water from the soils, and total amounts of Cu or Zn released from the soils increase, but the Cu or Zn concentration in the surface runoff decrease with increasing rainfall intensity. The increased Ca concentration in soil solution increased stability of organic matter-mineral complexes and might decrease the dissolution of organic matter, and thus decreased the release of Cu-binding component of organic matter. However, high concentration of Na in the soil solution increased the dispersion of the organic matter-mineral complexes and increased dissolution of organic matter and the release of Cu from the soils.
文摘The property of hydrophilic polymers capable absorbing huge volumes of water led to many practical applications of these new materials in arid regions for improving the water retention in sandy soils. Effects of four carboxymethylcelluloses （CMC） mixed at various rates with the sandy soil, on the water-holding capacity and hydraulic conductivity （Ks） when leached with distilled water （simulating rain）, tap water, and saline water were evaluated. The maximum water absorption of CMCs ranged between 80 and 100 kg. kg^-1 of polymer; however, the absorbent swelling capacity decreased significantly with increasing the salt concentration in the solution. The water absorption capacity of CMCs decreased significantly when incorporated in the sandy soil compared to that of the absorbent alone. Application of CMC increased significantly the available water content up to 3 ± 0.5 times. All soils treated with CMCs showed a significant lower in Ks compared to the control soil. Meanwhile, Ks was found increased with increasing the salt concentration in the leaching solution. This understanding of characteristics of the absorbents and the interactions among absorbents, soil, and irrigation water quality would be of help in water management of sandy soil
文摘With the aim to apply the beneficial microorganisms to peanut （groundnut （Arachis hypogaea）） growing in sandy soil of Binhdinh province in Vietnam, the paper was conducted to study the isolation, selection of N-fixing, phosphate, potassium solubilizing and slime producing microorganism from sandy soil and peanut root samples, and evaluate the capability of selected isolates to adapt to the sandy soil condition. The isolation and selection of beneficial microbes were based on the biological activity of isolates, which was determined by acetylene reduction assay and nodulation on the peanut for Rhizobium spp., by testing the capability to solubilize Ca3（PO4）2 or fenspat in the growth medium for phosphate, potassium solubilizing microbes, and by measurement of the viscosity of Hansen medium for slime producing microorganism. All isolates were evaluated for the effectiveness on the nutrition uptake and growth of peanut by carrying out at the greenhouse and field experiments. To evaluate the adaptation of selected isolates to the sandy soil condition, the experiments were carried out in the laboratory to determine the microbial density in suitable medium, containing different NaCI concentrations or with different pH or at different temperatures. The results showed that rhizobial strain RA18 had an N-fixing activity value of 3,458 ＋ 10.95 nmol C2H2/plant and can supply 30% of N required for peanut. The bacterial strain P 1107 is able to solubilize phosphate and can increase phosphorus uptake by 30% in peanut. Further, inoculation of peanut with the bacterial strain S3.1 can save 30% required mineral potassium, and the Lipomyces strain PT5.1 can produce the slime, which can provide the sandy soil to keep moisture for 15 d longer than the control without the inoculation. All selected isolates are able to grow at temperatures from 20 ℃ to 35 ℃, pH from 4.5 to 6.0 and the salinity of 0.2%o-0.6%o NaCI, and can well adapt to the sandy soil conditions.
文摘In this paper, a study of sandy soil compaction with different granulometry and moisture content has been performed, and soil mechanical property variations in moisture and granulometry have been investigated. Investigations were performed to compare hydrostatic compression test （HCT） responses and evaluate the compression index, Cc, which is an indicator of the soil＇s susceptibility to compaction-induced damage. The experiments have been performed on 24 soil samples typologies. Each sample has been obtained by combining three types of soil granulometry （types A, B and C） with a relative content varying from 0% to 100% in 20% increments. Soil type A had a granulometry ranging between 0.5 mm and 1 mm, type B between 0.25 mm and 0.5 mm, and type C less than 0.25 mm. These samples were representative of a sandy soil, chemically inactive and had various granulometries and initial moisture contents. A cell for HCT has been set up to allow the initial volume measurement of the test pieces and the subsequent changes during HCT with an estimated error less than 0.1 cm3. All samples were pre-compacted and prepared in agreement with the actual standards. The experimental data are reported in diagrams, the data allowed comparison of the mechanical behaviors between the considered unsaturated soils and underlined how soil moisture and granulometry affect soil response during HCT. Furthermore, because of the methodology used, the equipment was very economical.
文摘The sandy soils of Mostaganem plateau are vety, poor in clay. They are characterized by very low fertility and water holding capacity. The addition of bentonite to these soils and the cultivation of durum wheat, in combination with the chickpeas, are two eco-physiological strategies to rehabilitate their agricultural suitability. This study was conducted on two plant species： a local variety of durum wheat （Waha） and a legume, chickpea （variety ILC 3279）, on a substrate bentonite at 10% dose. For each stage of growth measurements of stem height, leaf area and plants vegetative nitrogen content were quantified. Changes in total nitrogen content of durum wheat grown in substrates amended with 10% bentonite or not during the development of durum wheat in monoculture and in association with the chickpeas were analyzed. The results showed that the total nitrogen content of durum wheat was significantly higher at three leaves and tailoring stages, when durum wheat was associated with chickpea in the same soil. However, the results showed no difference during the lifting and two leaves stages. There was also a positive effect of treatment at 10% of bentonite on the plant total nitrogen content regardless of the stage and the culture system.
