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Viscoelasticity and shear resistance at the aggregate scale of structured and organic carbon-free Chernozems

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Pedosphere 2023年第5期33卷 754-764页

作者： Christoph HAAS rainer.horn Philipp SAGGAU rainer DUTTMANN Institute for Plant Nutrition and Soil Science University of KielKiel 24118Germany Department of Geography Division of Landscape Ecology and Geoinformation SciencesUniversity of KielKiel 24118Germany

Soil rheology characterises the flow behaviour of soils at the particle-particle to aggregate *** sweep tests(ASTs)are often the method of choice for parameterizing soil flow properties,such as the shear strain values at the end of the linear viscoelastic range(i.e.,the deformation is mainly elastic)and at the yield point(i.e.,elastic equals plastic deformation).Samples from seven soil profiles and five soil depths of Chernozems,collected in the Maidanetske study area,close to Uman City of Ukraine,were analysed to evaluate the effect of soil organic carbon(SOC)on the parameters related to soil microstructural stability derived from *** organic carbon was removed with H_(2)O_(2)to determine the soil texture-dependent values of soil rheological properties,which were compared to the values determined for samples with intact water-stable *** shear resistance-related parameters increased for aggregated soil samples compared to SOC-free soil samples,indicating an increase in soil stability due to *** contrast,the values of the overall viscoelasticity and the shear strain were reduced for aggregated soil samples,indicating decreased soil *** functions were applied to predict the shear strain-dependent loss and storage moduli and shear stress values as a function of SOC *** particles(630–2000μm)and volumetric water content improved the *** conclude that increased SOC content,through the gluing and cementing effects of SOC and altered aggregate shapes compared to SOC-free soil materials,contributes to higher microstructural ***,the increased water content in the SOC-containing soil samples reversed soil strengthening *** was due to the fact that a more rapid increase in positive water pressure under shear stress weakened the samples and the spherical aggregates began to rotate more easily,thus loosing energy,when compared to platy particles of the SOC-free soil materials.

关键词： aggregation rheology shear strain shear stress soil organic carbon depletion soil stability

Biochar-Induced Changes in Soil Resilience:Effects of Soil Texture and Biochar Dosage

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Pedosphere 2017年第2期27卷 236-247页

作者： Ayodele Ebenezer AJAYI rainer.horn Department of Agricultural and Environmental Engineering Federal University of Technology 340252 Akure Ondo State (Nigeria) Institute for Plant Nutrition and Soil Science CAU Kiel 24118 Kiel (Germany)

Biochars are, amongst other available amendment materials, considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions. The latter is widely discussed as a consequence of improved physical quality of the amended ***, the mechanisms for this improvement are still poorly understood. This study investigated the effect of woodchip biochar amendment on micro-structural development, micro-and macro-structural stability, and resilience of two differently textured soils,fine sand(FS) and sandy loam(SL). Test substrates were prepared by adding 50 or 100 g kg^(-1) biochar to FS or SL. Total porosity and plant available water were significantly increased in both soils. Moreover, compressive strength of the aggregates was significantly decreased when biochar amount was doubled. Mechanical resilience of the aggregates at both micro-and macro-scale was improved in the biochar-amended soils, impacting the cohesion and compressive behavior. A combination of these effects will result in an improved pore structure and aeration. Consequently, the physicochemical environment for plants and microbes is improved. Furthermore, the improved stability properties will result in better capacity of the biochar-amended soil to recover from the myriad of mechanical stresses imposed under arable systems, including vehicle traffic, to the weight of overburden soil. However, it was noted that doubling the amendment rate did not in any case offer any remarkable additional improvement in these properties, suggesting a further need to investigate the optimal amendment rate.

关键词： aggregate stability amendment material compressive strength rheometry shear properties total porosity

Effect of land-use management systems on coupled physical and mechanical,chemical and biological soil processes:how can we maintain and predict soil properties and functions?

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Frontiers of Agricultural Science and Engineering 2020年第3期7卷 243-245页

作者： rainer.horn Winfried E.H.BLUM Institute of Plant Nutrition and Soil Science 24118 KielGermany Institute of Soil Research University of Natural Resources and Life Sciences(BOKU)1190 ViennaAustria

Soil is one of the most critical life-supporting components of the biosphere. Soil provides many ecosystem services,such as a habitat for biodiversity, water and nutrients, food, feed, fiber and energy, but also serves as archaeologicalrepositories. In addition to natural changes in pedological properties and functions over the course of time (soilgenesis), their properties also undergo intense and irreversible changes due to a non-site adjusted landmanagement and improper application of machinery, sealing and techniques as well as chemical impacts includingacidity from acid rain, heavy metals pollution and salinity.

关键词： soil maintain sealing

Nutrient uptake,maximum yield production,and economic return of maize under deficit irrigation with biochar and inorganic fertiliser amendments

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Biochar 2019年第4期1卷 375-388页

作者： Oluwaseun Temitope Faloye Ayodele Ebenezer Ajayi Michael Olarewaju Alatise Babatunde Sunday Ewulo rainer.horn Department of Agricultural and Environmental Engineering Federal University of TechnologyAkureNigeria Department of Agricultural and Food Engineering Afe Babalola UniversityAdo EkitiNigeria Department of Crop Soil and Pest ManagementFederal University of TechnologyAkureNigeria Institute for Plant Nutrition and Soil Science CAU KielHermann Rodewaldstr.224118 KielGermany

The individual and combined effects of biochar(B)and inorganic fertiliser(F)have all been widely proofed to improve soil fertility and enhance crop growth and yield under irrigation(I)and rain fed ***,the strength of their individual and combined effects on crop productivity has been scarcely *** addition,few studies have assessed their individual and co-application effects on economic ***,a 2-year field experiment which consisted of factorial combination of irrigation(I)[100%full irrigation(FI),80%FI and 60%FI],biochar(0 and 20 t/ha)and fertiliser(0 and 300 kg/ha)was *** to the results,irrigation was the dominant factor that influences maize grain yield,followed by inorganic fertiliser and biochar,and they were all significant in their main *** strength of interaction effects among,I,F and B on maize grain yield follow the sequence F×I>B×F>B×*** economic analysis showed that the ternary combination of B,F and I was more economical than the binary combination of B plus I,and F plus I(in that order),when compared with the standalone application of I at maximum production in the field *** addition,combined applications of biochar and fertiliser improved soil nutrients,nutrient uptake in all irrigation treatments,compared to the standalone applications of biochar or *** research is,therefore,recommended for long-term evaluation of the economic viability of integrating biochar with fertiliser under irrigation.

关键词： Biochar amendment Drip irrigation Maize grain yield Economic evaluation Optimum irrigation

Investigation of time dependent development of soil structure and formation of macropore networks as affected by various precrop species

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International Soil and Water Conservation Research 2014年第2期2卷 51-66页

作者： Sebastian K.Pagenkemper Daniel Uteau Puschmann Stephan Peth rainer.horn Dept.of Soil Science Institute of Plant Nutrition and Soil ScienceUniversity of KielGermany Dept.of Soil Science Organic Agriculture SciencesUniversity of KasselGermany

A well developed macropore network is advantageous in terms of transport processes regarding gas and water,as well as nutrient acquisition and root growth of crops.X-ray computed tomography provides a non-destructive method to visualize and quantify three-dimensional pore *** and morphological parameters of the complex pore system such as connectivity,tortuosity,porosity and pore surface area would be very useful for modeling and simulation of transport and exchange processes by providing quantitative data on relevant soil structural features and their modification by soil *** scope of this study was to analyze and quantify the development of soil structure in the subsoil depending on three different precrop species(alfalfa A,chicory C and fescue F),at three depths(45,60 and 75 cm)and cultivation periods(1,2 and 3 years).Furthermore,morphological(air-filled porosityθa,pore surface area)and geometrical(pore diameter,connectivity,continuity,tortuosityτ)parameters were gathered with X-ray CT and image *** an experimental field trial(Germany)with a Haplic Luvisol as soil type samples were taken and ***-capacity(θa)was measured in the laboratory for the same cylinders and compared to the results derived by image ***-capacity was highest for alfalfa(3 years,75 cm).Tortuosity(τ)ranged between 1.3 and 4.38,while alfalfa(3 years)showed the highest value,which indicated structural development due to crack formation by enhanced root water ***,an increase in accessible surface may improve water and nutrient supply for plants,whereas the highτvalues may assume that oxygen supply is *** was found that the interaction of gas-diffusivity and the calculated parameters should be further investigated in terms of limitations to plant growth.

关键词： Biological tillage Image analysis Batch processing Subsoil structure Dynamic development

Soil Wettability as Affected by Soil Characteristics and Land Use

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Pedosphere 2010年第1期20卷 43-54页

作者： R. horn Institute of Plant Nutrition and Soil Science Christian-Albrechts-University zu Kiel

Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettability was evaluated by contact angle with the Wilhelmy plate method. Water repellency was likely to be present under permanently vegetated land, but less common on tilled agricultural land. It was mostly prevalent in the topsoil, especially in coarse-textured soils, and decreased in the subsoil. However, the depth dependency of wettability could not be derived from the investigated wide range of soils. The correlation and multiple regression analysis revealed that the wettability in repellent soils was affected more by soil organic carbon (SOC) than by soil texture and pH, whereas in wettable soils, soil texture and pH were more effective than SOC. Furthermore, the quality of SOC seemed to be more important in determining wettability than its quantity, as proofed by stronger hydrophobicity under coniferous than under deciduous forestland. Soil management had a minor effect on wettability if conventional and conservation tillage or different grazing intensities were considered.

关键词： soil management soil organic carbon soil pH soil texture

Friction between a temperature dependent viscoelastic body and a rough surface

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Friction 2016年第1期4卷 50-64页

作者： rainer HEISE Institute for Mechanics Technische Universit(a)t Berlin Straβe des 17.Juni 135 Berlin D-10623 Germany

In this study, we investigate the friction between a one-dimensional elastomer and a one-dimensional rigid randomly rough surface. Special emphasis is laid on the temperature dependence of the elastomer and its effect on the frictional behavior of the contact. The elastomer is modeled as a Kelvin body in a one-dimensional substitute model in the spirit of the method of dimensionality reduction. The randomly rough surface is a self-affine one-dimensional fractal. We provide a short discussion of a conical indenter pressed in a displacement controlled process into an elastomer. These analytical considerations are taken as a basis for the treatment of the randomly rough counter surface in contact to an elastomer with and without temperature dependent viscosity. We identify dimensionless quantities describing this process, introduce a thermal length scale, and give estimates for the coefficient of friction as function of velocity, indentation and thermal quantities.

关键词： elastomer friction temperature dependence coefficient of friction

Stochastic Differential Games with Reflection and Related Obstacle Problems for Isaacs Equations

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Acta Mathematicae Applicatae Sinica 2011年第4期27卷 647-678页

作者： rainer BUCKDAHN Département de Mathématiques Université de Bretagne Occidentale6avenue Victor-le-GorgeuB.P.80929285 Brest cedexFrance Institute for Advanced Study Shangdong UniversityJinan 250100China

In this paper we first investigate zero-sum two-player stochastic differential games with reflection, with the help of theory of Reflected Backward Stochastic Differential Equations （RBSDEs）. We will establish the dynamic programming principle for the upper and the lower value functions of this kind of stochastic differential games with reflection in a straightforward way. Then the upper and the lower value functions are proved to be the unique viscosity solutions to the associated upper and the lower Hamilton-Jacobi-Bettman-Isaacs equations with obstacles, respectively. The method differs significantly from those used for control problems with reflection, with new techniques developed of interest on its own. Further, we also prove a new estimate for RBSDEs being sharper than that in the paper of E1 Karoui, Kapoudjian, Pardoux, Peng and Quenez （1997）, which turns out to be very useful because it allows us to estimate the LP-distance of the solutions of two different RBSDEs by the p-th power of the distance of the initial values of the driving forward equations. We also show that the unique viscosity solution to the approximating Isaacs equation constructed by the penalization method converges to the viscosity solution of the Isaacs equation with obstacle.

关键词： stochastic differential games value function reflected backward stochastic differential equations,dynamic programming principle Isaacs equations with obstacles viscosity solution

Influence of slant of objective on image formation in optical microscopes

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Chinese Optics Letters 2008年第8期6卷 603-606页

作者： rainer Kning Physikalisch-Technische Bundesanstalt Braunschweig Bundesallee 10038116 BraunschweigGermany

A microscope image formation model based on scalar diffraction and Fourier optics has been developed, which takes a slant angle between the optical axis and the observed surface into account. The theoretical investigations of the imaging of line structures using this model show that reflection type microscopes are much stronger influenced by the slant angle than transmission type microscopes. In addition, the slant angle changes the image contrast and the image shape of a line structure, especially its edge. The larger the slant angle, the stronger the decrease of the image contrast, and the less steep the edge slope in both types of microscopes. Furthermore, the larger the numerical aperture of the objective, the less the effect of the slant angle on the line image shape.

关键词： line this