Prospects and limitations of soil amendment and irrigation techniques for the water-saving public urban greenery and ephemeral weed management in the sandy soils of the United Arab Emirates

Public urban greenery greatly contributes to the residential and tourist value of cities in the Gulf Region,but due to the hyper-arid climatic conditions,the cost of irrigation and plant maintenance is very high.Existing strategies to reduce the monetary and ecological costs involve the cultivation of native xerophytic plantations,and/or the use of soil improvers to increase water-and nutrient-holding capacity of the sandy soils.Various soil improvers based on mineral,organic,or synthetic materials have entered the United Arab Emirates(UAE)market in recent years,but there is considerable uncertainty about how they should best be used in combination with ornamental plant stands involving xerophytic native plants.The present study investigated the effect of soil amendment and deep pipe irrigation on perennial ornamental plant stands involving native plants(Tephrosia appolinea(Gel.)Link in combination with Aerva javanica(Burm.f.)Juss.ex Schult.)and native-exotic plants(T.appolinea in combination with Ruelia simplex C.Wright)either or not topsoil and subsoil amendment with bentonite and hydrophobic sand under the irrigation water supply of less than 50%of reference evapotranspiration(ET0).After one year of cultivation,T.appolinea and A.javanica(native vs.native)produced high biomass and exhibited high water use efficiency(WUE)as compared with T.appolinea and R.simplex(native vs.exotic)combination given that no significant differences were found under the soil amendment treatments.All stands thrived under irrigation water supply far below what is usually supplied to exotic ornamental stands in public parks of the Al Ain City,the UAE.However,subsoil amendment in combination with deep pipe irrigation reduced the occurrence of weeds and increased the overall plant rooting depth.Our results suggest that subsoil amendment and irrigation up to 60-80 cm depth can potentially control ephemeral weed infestation,which is a great challenge in various plant production systems of the Gulf Region.The results of the present study suggest that the impact of soil amendment on the WUE of exotic plants is marginal and might not be economically justified.Replacing exotic with native ornamental plant species seems to have a far greater water-saving potential than the amendment of the soil,while weeds can be suppressed in the absence of topsoil moisture.

In situ digital testing method for quality assessment of soft soil improvement with polyurethane

This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring method.These factual drilling data can characterize the degree of soil improvement by penetration injection with permeable polyurethane.Result from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement vs.net drilling time,which indicates the spatial distributions of soil profile.The soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky soil.The results of soil profile are verified by the parallel site loggings.The constant drilling speeds profile the coring-resistant strength of drilled soils.By comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty clay.Laboratory tests,i.e.uniaxial compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling speeds.Results show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty clay.The UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ method.This method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.

Effects of Microbial Fertilizers on Soil Improvement and Wheat Growth Characteristics in Saline-alkali Land

[Objectives]This study was conducted to further enrich the research on saline-alkali land improvement,and explore the effects of biological bacterial fertilizers containing Bacillus subtilis and Bacillus velezensis HM-3 in saline-alkali land improvement and crop growth promotion.[Methods]Wheat was planted in saline-alkali land in Huanghua City,Hebei Province,and a mixed application experiment was carried out using biological agents from Hemiao Biotechnology Co.,Ltd.[Results]Compared with the field of control check(CK),water-soluble salts and pH value in the experimental fields decreased,and living bacteria count in the soil increased.Meanwhile,the economic characters of wheat in the experimental fields showed excellent performance,with yields increasing by 39.09%and 27.49%compared with the CK.It could be seen that the application of biological bacterial fertilizers achieved obvious effects of improving saline-alkali soil and increasing wheat yield.[Conclusions]In this study,the effects of biological bacterial fertilizers on saline-alkali land and wheat growth characters were clarified,providing some technical support and theoretical guidance for wheat planting in Huanghua saline-alkali land.

An Overview of Soil Improvement through Ground Grouting

Soil is an essential component of what surrounds us in nature, providing as the basis for our infrastructure and construction. However, soil is not always suitable for construction due to a variety of geotechnical issues such as inadequate bearing capacity, excessive settlement, and liquefaction susceptibility. Through improving the engineering qualities of soil, such as strength, permeability, and stability, ground grouting is a specific geotechnical method used. Using a fluid grout mixture injected into the subsurface, holes are filled and weak or loose strata are solidified as the material seeps into the soil matrix. The approach’s adaptability in addressing soil-related issues has made it more well-known in the fields of civil engineering and construction. In the end, this has improved groundwater management, foundation support, and overall geotechnical performance.

Densification of Reclaimed Soils with the Utilization of the Vibro Compaction Technique—A Case Study

This paper presents a case study of the extensive soil improvement work carried out on a reclamation project on the shores of United Arab Emirates. The project consisted an area of approximately 480,000 m2 for recreation purposes. Following the dredging work, approximately 6.8 million cubic meters underwent densification using the vibrocompaction method. The general aims of such analysis are to investigate the effectiveness of vibrocompaction as a method of soil improvement and appraise the selection of this method as the most appropriate soil treatment technique necessary for the adequate densification of the overall loose soil masses. The efficiency of the vibrocompaction technique to densify thick granular-based soil formations of considerable thickness and the benefits obtained, equated to other soil treatment methods, was assessed through a comprehensive post quality control program including field and laboratory post-compaction testing. Based on the analysis conducted it is concluded that soil strength of the reclaimed materials achieved a noteworthy improvement reaching comfortably the required degrees of densification.

Effects of Biochar on Tobacco-planting Soil Improvement and Tobacco Quality in Mudanjiang Area

This study was conducted to study the feasibility of biochar in soil im- provement and tobacco quality. The black soil in NinganCountry of Mudanjiang was used as the material in this study, and the effects of biochar on tobacco-planting soil C/N, soil microorganisms, the development of tobacco, and chemical compo- nents and neutral aroma components in flue-cured tobacco werestudied. The results showed that the application of biochar at a rate of 1 800 kg/hm2 could increase soil C/N by 31.79%, and the quantity of actinomycetes in the soil was 3.8 times as much as that in control. The growth wasobviously better after biochar application, plant height and effective leaf number were significantly higher than those ofcontrol, but total sugar and nicotine were not significantly different. The application of biochar at a rate of 1 200 kg/hm2 increased the potassium content by 11%, the application of biochar at a rate of 2 400 kg/hm2 improved total sugar content by 5.40%, and the application of biochar at a rate of 1 800 kg/hm2 made the tobacco solanone content 1.97 times as that of control. Comprehensive studies showed that the application of biochar 1 200-1 800 kg/hm2 could improvesoilenvironment, and promote tobacco growth and quality.

Modelling smear effect of vertical drains using a diameter reduction method

Vertical drains are used to accelerate consolidation of clays in ground improvement projects.Smear zones exist around these drains,where permeability is reduced due to soil disturbance caused by the installation process.Hansbo solution is widely used in practice to consider the effects of drain discharge capacity and smear on the consolidation process.In this study,a computationally efficient diameter reduction method(DRM)obtained from the Hansbo solution is proposed to consider the smear effect without the need to model the smear zone physically.Validated by analytical and numerical results,a diameter reduction factor is analytically derived to reduce the diameter of the drain,while achieving similar solutions of pore pressure dissipation profile as the classical full model of the smear zone and drain.With the DRM,the excess pore pressure u obtained from the reduced drain in the original un-disturbed soil zone is accurate enough for practical applications in numerical models.Such performance of DRM is independent of soil material property.Results also show equally accurate performance of DRM under conditions of multi-layered soils and coupled radial-vertical groundwater flow.

Effects of Continuous Cropping on Soil Microbial Flora and Research Progress of Continuous Cropping Obstacle Reduction Techniques

Continuous cropping can bring economic benefits in a short time and meet the growing demand of agricultural products such as grain,but long-term continuous cropping will accelerate soil degradation,lead to the reduction of crop yield and the increase of disease rate,and destroy the balance of soil microbial structure.Therefore,it is not conducive to the sustainable development of soil ecosystem.In this paper,the problems caused by continuous cropping,such as imbalance of soil microbial flora,decrease of biodiversity,accumulation of root exudates and their effects on soil fertility and crop growth,were summarized,and some measures were suggested to alleviate the obstacles of continuous cropping,such as reasonable rotation,adjustment of intercropping planting mode and application of biological fertilizers.Moreover,the paper also looked forward to the development trend of continuous cropping obstacle reduction techniques,including the integration and application of biological techniques,the promotion of green ecological techniques and the application of intelligent management system.This study provides theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promote the healthy and sustainable development of modern agriculture.

Research Progress on Effects of Continuous Cropping on Soil Microbial Florae and Its Restoration

Continuous cropping has become a common form of agricultural production at present, but with the increase of continuous cropping years, continuous cropping obstacles such as soil-borne diseases and plant growth potential decline are becoming more and more common. At present, the causes of continuous cropping obstacles and continuous cropping restoration have become a hot issue in agricultural research. This paper summarized the effects of continuous cropping obstacles on soil microbial community structure and main technical methods to repair continuous cropping obstacles, such as agricultural measure management, microbial balance adjustment and soil improvement, aiming to provide theoretical reference for protecting the sustainable utilization of soil ecosystem and ensuring the stability of crop production.

Impact of Continuous Cropping on Soil Phenolic Acid Substances and Research Progress on Continuous Cropping Obstacle Reduction Techniques

At present,long-term continuous cropping in agricultural production has formed a relatively common development trend.With the increase of continuous cropping years,soil phenolic acids are also affected to varying degrees.This paper summarized the effects of continuous cropping on soil phenolic acids and the research progress of continuous cropping obstacle reduction techniques,aiming at providing theoretical basis and technical support for the research of continuous cropping obstacle reduction techniques and promoting the healthy and sustainable development of modern agriculture.

Steel Slag as an Iron Fertilizer for Corn Growth and Soil Improvement in a Pot Experiment

The feasibility of steel slag used as an iron fertilizer was studied in a pot experiment with corn. Slag alone or acidified slag was added to two Fe-deficient calcareous soils at different rates. Results showed that moderate rates (10 and 20 g kg-1) of slag or acidified slag substantially increased corn dry matter yield and Fe uptake. Application of steel slag increased the residual concentration of ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA) extractable Fe in the soils. The increase of extractable Fe was usually proportional to the application rate, and enhanced by the acidification of slag. Steel slag appeared to be a promising and inexpensive source of Fe to alleviate crop Fe chlorosis in Fe-deficient calcareous soils.

Numerical simulations of shake-table experiment for dynamic soil-pile-structure interaction in liquefi able soils

A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation(u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled(u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fi xed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively infl uence the lateral pile displacements.

Improvement of silty clay by vacuum preloading incorporated with electroosmotic method

A laboratory test was performed to assess the effectiveness of vacuum preloading incorporated with electroosmotic (EOM) treatment on silty clay (combined method) for reclamation projects like new disposal ponds, where the horizontal electrode configurations beneath the soil layer were possible and the drainage pipes and the prefabricated vertical drains (PVDs) system could be easily installed in advance before the sludge dragged from sea bed or river bed was filled into the site. Three groups of tests were conducted on the silty clay from Qinhuai River in Nanjing, China. The model is able to apply vacuum pressure at the bottom of the soil layer and a direct current electric field simultaneously. It is also possible to measure the pore pressures at different depths of soil column, and the changes in settlement and volume with the elapsed time. In this study, the vacuum preloading method, vacuum preloading applied at the bottom (VAB method), was applied and the cathodes were installed beneath the soil layer. The results obtained indicate substantial reduction in water content, and increases in dry density and undrained shear strength in comparison with those obtained by the vacuum preloading only, particularly at the positions close to the anode. The combined method utilizes the vertical drainage flow created by the electroosmosis integrating the horizontal drainage flow created mostly by the vacuum pressure. The total drainage flow can be calculated as a result of the vertical drainage flow by electroosmosis only and the horizontal drainage flow by the vacuum preloading only. The way of placement of the cathode and the anode in the combined method also overcomes the disadvantage of EOM method itself, i.e. the appearance of cracks between the anode and the surrounding soil. Moreover, it is observed that the vacuum preloading plays a primary role in earlier stage in deduction of free pore water; meanwhile, the electroosmotic method is more efficient in later stage for absorbing water in the diffused double layers of soil.

Biological process of soil improvement in civil engineering:A review

The concept of using biological process in soil improvement which is known as bio-mediated soil improvement technique has shown greater potential in geotechnical engineering applications in terms of performance and environmental sustainability. This paper presents a review on the soil microorganisms responsible for this process, and factors that affect their metabolic activities and geometric compatibility with the soil particle sizes. Two mechanisms of biomineralization, i.e. biologically controlled and biologically induced mineralization, were also discussed. Environmental and other factors that may be encountered in situ during microbially induced calcite precipitation （MICP） and their influences on the process were identified and presented. Improvements in the engineering properties of soil such as strength/stiffness and permeability as evaluated in some studies were explored. Potential applications of the process in geotechnical engineering and the challenges of field application of the process were identified.

Improvement of geotechnical properties of sabkha soil utilizing cement kiln dust

Improvement of properties of weak soils in terms of strength,durability and cost is the key from engineering point of view.The weak soils could be stabilized using mechanical and/or chemical methods.Agents added during chemical stabilization could improve the engineering properties of treated soils.Stabilizers utilized have to satisfy noticeable performance,durability,low price,and can be easily implemented.Since cement kiln dust(CKD) is industrial by-product,it would be a noble task if this waste material could be utilized for stabilization of sabkha soil.This study investigates the feasibility of utilizing CKD for improving the properties of sabkha soil.Soil samples are prepared with 2% cement and 10%,20% or 30% CKD and are tested to determine their unconfined compressive strength(UCS),soaked California bearing ratio(CBR) and durability.Mechanism of stabilization is studied utilizing advanced techniques,such as the scanning electron microscope(SEM),energy dispersive X-ray analysis(EDX),backscattered electron image(BEI) and X-ray diffraction analysis(XRD).It is noted that the sabkha soil mixed with 2% cement and 30% CKD could be used as a sub-base material in rigid pavements.The incorporation of CKD leads to technical and economic benefits.

An improved Mesri creep model for unsaturated weak intercalated soils

The weak intercalated soils in redbed soft rocks of Badong formation have obvious creep characters. In order to predict the unsaturated creep behaviors of weak intercalated soils, an unsaturated creep model was established based on the unsaturated creep tests of weak intercalated soils by using GDS triaxial apparatus. The results show that the creep behaviors of intercalated soils are apparent and significantly affected by matric suction. Based on this, an empirical Mesri creep model for intercalated soils under varying matric suctions was built. The fitting results show that the parameters Ed and m of this model are in good power relations with matric suction s and stress level Dr, respectively. An improved Mesri creep model was established involving stress-matric suction-strain-time, which is more precise than the Mesri creep model in predicting the unsaturated creep behaviors of weak intercalated soils.

Emission control for precursors causing acid rain(V): Improvement of acid soil with the bio-briquette combustion ash

The bio-briquette technique which mixes coal, biomass and sulfur fixation agent and bio-briquettes under 3—5 t/cm 2 line pressure has aroused people's attention in view of controlling the air pollution and the acid rain. In this paper, the physicochemical properties of bio-briquette and its ash were investigated. And the acid soil was improved by the bio-briquette combustion ash, which contained nutritive substances such as P, N, K and had the acid-neutralizing capacity(ANC). The pH, EC, effective nutrient elements(Ca, Mg, K, P and N), heavy metal elements(Al, Cu, Cd, Cr, Zn and Mn) and acid-neutralizing capacity change of ash-added soils within the range of 0—10%, were also studied. Specially, when 5% bio-briquette combustion ash was added to the tested soil, the content of the effective elements such as Ca, Mg and K rose by 100 times, 7 times and twice, respectively. The total nitrogen also increased by about twice. The results showed the oxyanions such as that of Al, Cu, Cd, Cr, Zn and Mn were not potentially dangerous, because they were about the same as the averages of them in Chinese soil. It is shown that the ANC became stronger, though the ANC hardly increases in the ash-added soil. On the basis of the evaluation indices, it is concluded that the best mixture ratio is to add 2.5%—8% of the bio-briquette combustion ash to the tested soil.

Study on Soil Improvement Measure of Plant Landscape Construction in Saline and Alkaline Area in Tianjin

A detailed research in soil improving measure was conducted during the process of plants that were cultivated in Tianjin saline and alkaline area. The results showed that the commonly used measures could improve the soil, and also we got some useful advices and suggestions for plants cultivating in Tianiin saline and alkaline areas.

Improvements of marine clay slurries using chemicale-physical combined method(CPCM)

In this paper, the effectiveness, applicability and validity of chemicalephysical combined methods（CPCMs） for treatment of marine clay （MC） slurries were evaluated. The method CPCM1 combineschemical stabilization and vacuum preloading （VP）, while CPCM2 is similar to CPCM1 but includes boththe application of surcharge and use of geo-bags to provide confinement during surcharge preloading.The key advantage of CPCM2 using geo-bags is that the surcharge can be immediately applied on thechemically stabilized slurries. Two types of geo-bags were investigated under simulated land filling anddyke conditions, respectively. The test results show that the shear strength （cu） of treated slurry byCPCM2 is generally much higher than that by CPCM1. Besides, the use of CPCM2 can significantly reducethe treatment time due to the short drainage paths created by geo-bags. Overall, CPCM2 allows fasterconsolidation and higher preloading that help to achieve higher mechanical properties of the stabilizedslurry. There are consistent relationships between cU and water content of slurries treated by CPCM2.Several important observations were also made based on comparisons of experimental data. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Functions of Russian Melilotus officinalis on Degraded Soil Improvement

To improve the serious situation of soil degradation in China, tests were carried out to study the improvement effects of Russian Melilotus officinalis on the low base saturation acid soil, the alkaline-saline soil and the heavy metal contaminated soil. The results showed that M. officinalis could improve the low base saturation acid soil, increase the salt, alkali content, mineral nutrition and organic nutrient, which indicated that M. officinalis could be planted in the acid soil, and had a significant ecological effect on soil improvement. M. officinalis achieved a remarkable effect on improving the alkaline-saline soil （pH 8.5-9.5） that the soil desalted, dealkalized and had more organic nutrient. Moreover, M. officinalis could improve the heavy metal contaminated soil and had the ability to enrich and transform heavy metal elements, especially Cd and Ni, thereby presenting significant repair effects on soil improvement. Therefore, Russian M. officinalis had multiple-effects on degraded soil improvement, so it is worthy of application and popularization.