A method for assessing the impact of load on mechanical stability and on physical properties of soils

Methods to quantify the mechanical strength of agricultural soils in order to assess the trafficability are presented. The pedotransfer functions relating the precompression stress as a measure of soil strength and the depending soil parameters are also shown. By using cohesion and angle of internal friction values, the precompression stress can be calculated using the multiple regression equations. Horizon specific values on the mechanical stability of arable soils is determined at various moisture suctions. Changes in dependence of gravel contents are also given. The stress transmission for specific soil horizons is calculated by using classified values of the concentration factor. The mechanical stability for the soil profile is then determined by comparing the actual pressures in a specific soil horizon with the corresponding value of the precompression stress. Stress dependent changes of soil physical properties only occur when applied stress exceeds the precompression stress. These changes in soil physical properties are dependent on soil suction, texture, structure and applied stress. Regression equations presented in this paper can be used to calculate the changes in soil physical and mechanical properties due to loading. The proposed method is a useful tool towards fulfilling the soil protection law in the Federal Republic of Germany.     

Land evaluation for forestry: a study of the land requirements for growing Pinus radiata D. Don in the Basque Country, northern Spain

Land requirements for the growth of Pinus radiata D. Don were studied in 112 plots by comparing site index (SI) values with land characteristics. The SI at the reference age of 20 years ranged from 10.4 to 32.7 m. The growth of Radiata pine increased as soil rootable depth increased, with a mean depth of about 50 cm in plots with an SI higher than 29 m. The results show that soil physical properties had a major influence on growth rates with soils of a loamy texture resulting in higher rates than clay rich soils. Soil nitrogen and phosphorus availability had significant effects on growth on soils developed on non‐volcanic parent material whilst potassium availability was significant in soils on volcanic parent material. There were strong interactions among the land characteristics of each land unit so that the magnitude of the specific effect of a given variable was highly dependent on the values of the others. Results are discussed in relation to land use planning.     

Uptake of lead by coen from roadside soil samples

Abstract

The uptake of Pb by young, greenhouse grown corn plants from roadside soil samples was found to be not only dependent upon the total amount of Pb in the soil, but also upon the amount of Pb in the soil relative to the soils capacity to sorb Pb. This is in agreement with the uptake of Pb by corn grown on soils amended with PbCl₂, although plant accumulation of Pb from roadside soils was much less than from PbCl₂ amended soils at comparable Pb concentrations. The use of crushed limestone as a road building material which results in high soil pH values next to the roadside is probably responsible for the reduced plant availability of Pb in the roadside soils.     

Specific features of iron behavior in soddy-podzolic and alluvial gleyed soils of the Middle Cis-Urals region

The regime of observations revealed that the Eh dynamics in soddy-podzolic and alluvial soils in the Middle Cis-Urals region depends not only on the rate of iron (hydr)oxides reduction but also on the rate of opposite reactions in the gleyed horizons. Both processes depend on the temperature. The Eh value decreases on heating in automorphic soils, when the reduction of Fe(III)-(hydr)oxide particles accelerates. On the contrary, in gley soils, the Eh decreases on cooling, probably, because of the reactions opposing the reduction of Fe(III)-(hydr)oxide particles, including Fe(II) fixation on the surface of mineral particles. Fe(III)-(hydr)oxides are, for the most part, preserved in gleyed soils of the Cis-Urals; the content of (Fe₂O₃)_dit reaches 3.3% with iron minerals being usually represented by goethite. The increase in moistening influences the soil parameters (i.e., the redoxpotential rH and the content of conventional red pigment Hem_conv) in an intricate manner. Both direct and reverse branches on the curve of the Hem_conv-rH dependence point to the equilibrium and nonequilibrium conditions in the soil. The reverse branch probably stands for the initial phase of gleying in strongly humified soils, where, despite extra electrons in the solution, the brown pigment in the form of Fe(III)-(hydr)oxides is preserved.     

2，4-二氯苯氧基乙酸在土壤中的吸附淋溶特性

农药在土壤中的吸附和淋溶特性是评价其环境行为的重要指标,特别是决定了其在土壤中的迁移性。本文分别利用振荡平衡法和柱淋溶法研究了2,4-二氯苯氧基乙酸（2,4-D）在不同土壤中的吸附和淋溶特性及其影响因素。结果表明,2,4-D在3种供试土壤上的吸附特性能较好地用线性吸附等温线拟合,吸附常数心在0．95-1．54L·kg^-1之间,很难被土壤吸附。影响2,4-D在土壤中吸附的因素主要是土壤pH值,其次是有机质含量。土壤pH值增高,离子态的2,4-D量增加,吸附减弱;2,4-D在土壤中具有较强的淋溶性,影响其淋溶性能的主要因素是土壤pH值,pH值越高,淋溶性能越强。     

几种有机酸对恒电荷和可变电荷土壤吸附Cu2+的影响

以恒电荷土壤(黄褐土和黄棕壤)和可变电荷土壤(红壤和砖红壤)为供试材料,研究了乙酸、草酸、酒石酸和柠檬酸对土壤吸附重金属铜离子(Cu2 )的影响。结果表明,在相同酒石酸浓度下,土壤对酒石酸的吸附量依次为黄棕壤(2 1 8mmolkg-1) >红壤(15 4mmolkg-1) >砖红壤(9 5mmolkg-1) ,土壤吸附有机酸后负电荷量增加,相同条件下增幅为砖红壤>红壤>黄棕壤;无有机酸配体时,供试土壤对Cu2 的吸附量为黄褐土>黄棕壤>砖红壤>红壤;加入有机酸时,随有机酸浓度增高,土壤对Cu2 的吸附一般表现为“峰”形曲线,峰所对应的有机酸浓度因有机酸类型而异,且随土壤可变电荷性质增强而增高;土壤吸附有机酸后对Cu2 的次级吸附不同于有机酸与铜共存时的竞争吸附,且因土壤性质表现迥异。这些结果意味着在存在有机酸配体的根际环境中,恒电荷土壤与可变电荷土壤对Cu2 的吸附明显不同,并将影响重金属离子在根际的转化与有效性     

Particle arrangement and internal porosity of coarse fragments affect water retention in stony soils

Information about water retention in stony soils lags behind due to methodological difficulties. We applied a new strategy to measure the water retention in soils with coarse fragments (CFs) and to get insights into the effect of CFs porosity on water retention. Water retention at zero, 10, and 150 m suction, bulk density, and the mass fraction of six particle size classes were measured in undisturbed blocks from soils with variable CFs contents, originating from three parent materials. The results showed that some soils contain porous CFs (2–250 mm) with a water holding capacity as high as the fine fraction (<2 mm). The water held in the suction range of 1–150 m in a soil with porous CFs was twice as high as in soils with non-porous CFs. Multilinear regressions revealed that both the water retention capacity at 1 m suction and in the range 1–150 m were more dependent on bulk density than on the fraction of CFs and fine particles. In the soil with porous CFs, there was no correlation between their fraction and soil water retention. These results show that the bulk water retention capacity of soils with CFs is underestimated when not considering the internal porosity of the CFs. A better understanding of the effect of the porosity of CFs on bulk soil porosity and water retention is important to propose suitable pedotransfer functions and refine physically-based hydraulic functions for stony soils.     

The concentrations of K,Rb and Cs in spruce needles (Picea abies Karst.) and in the associated soils

The elemental concentrations of K, Rb and Cs were determined in needles from individual spruce trees as a function of the needle age class. The concentrations are highest in current year's needles and decrease smoothly in older needles, approaching a constant value. Rb and Cs show similar behaviour, whereas that of K differs in so far as its relative decrease with time is less pronounced. Intra- and intersite variation of the needle concentrations are largest for Cs and smallest for K. Individual trees show a highly significant correlation between the log (Cs) and log (Rb) values. Total soil concentrations were determined at 9 sites with different parent material. Intra- and intersite variations of K are comparable for soils and for needles, whereas those for Rb and Cs are much smaller for soils than for needles. All three elements are correlated in soil samples. There is no close connection between soil and needle concentrations at the various sites. However, the results suggest that needle concentrations of Rb and Cs, but not of K, are strongly dependent on the sorption properties of the associated soils.     

Evaluation of Pb and Ni Mobility to Groundwater in Calcareous Urban Soils of Ancona, Italy

This study was performed on 21 soils with the aim of establishing whether Pb and Ni adsorption/desorption parameters could be considered as good indicators of the risk of groundwater pollution. Results showed that high pH values in soil caused a totally irreversible Pb adsorption, thus excluding any risk of Pb groundwater pollution. Sorption/desorption studies, quantified by the desorption index (DI), showed that Ni retention was only partly affected by the basic pH values but it was also due to the electrostatic attraction processes occurring on soil surfaces, as demonstrated by the partial reversibility of the Ni sorbed. This justifies possible risks of Ni groundwater pollution. The results of a monitoring research confirmed these findings. Results suggested that the adsorption/desorption parameters, namely DI, are promising indicators to predict the risk of groundwater pollution from metals in calcareous soils.     

Plant species affect the concentration of free sugars and free amino acids in different types of soil

Substantial amounts of low molecular weight organic compounds (LMWs) such as sugars and amino acids are transferred from plant roots into soil. These substances are released due to decomposition processes or leaching (exudation). Afterwards they can be metabolized by soil microorganisms into different compounds, or they can be partially re‐absorbed by the plants. The aim of this study was to clarify the influence of five wild plant species on the composition and pool sizes of LMWs extractable from three different soils. Four of the five species caused significant changes in soil LMW pools. In Chernozem, the sugar concentrations of soil with plants were up to 60 % higher than those of the bulk reference soil, and amino acids increased by as much as 207 %. The relative abundance of free amino acids in roots did not correlate with the relative abundance of amino acids in soil after six weeks of plant growth. The relative abundance of soil amino acids, that increased after plant growth, was strongly dependent on the type of soil and on the plant species present. We suggest that rather than rhizodeposition being dependent on soil type, it reflects differential microbial metabolization of amino acids in the respective soils.     

Modelling slaking sensitivity to assess the degradation potential of humid tropic soils under intense rainfall

In the humid tropics, soil erosion due to the impact of high‐intensity tropical rainfall is one of the important environmental problems. A quick assessment of slaking sensitivity of soils that are frequently subjected to the fast wetting of intense rainfall of the humid tropics is necessary for the selection of appropriate soil management practices to avoid soil structure deterioration that results in runoff, seal formation, erosion and eventual degradation. Unfortunately, field and laboratory measurements of slaking sensitivity are tedious, time consuming and expensive. Therefore, a slaking sensitivity ranking framework using readily available soil data, namely, clay content, organic matter content, exchangeable sodium percentage (ESP) and cation exchange capacity (CEC) determined to be important in slaking sensitivity and structural degradation under intense rainfall was developed. The ranking framework was subsequently used to classify 23 agriculturally important Trinidadian soils into slaking sensitivity classes for management recommendation. A simple mathematical model that provides a rapid assessment of slaking sensitivity was also developed using the soil data of 14 out of the 23 soils and subsequently tested on the remaining nine soils. Our results suggest that about 80 per cent or more of the soils are highly sensitive to slaking pressures, highly vulnerable to degradation and require management practices that reduce the rate of wetting and thus degradation of aggregates under intense rainfall. The developed model performed with a high degree of accuracy as the predicted values were in close agreement with measured values (r = 0·93). This suggests that the model gives a good indication of the structural degradation vulnerability of the soils studied under the conditions applied and criteria used. The model is, therefore, recommended for use in the tested humid tropical soils. However, more comprehensive testing is required on a broader range of soils prior to its more widespread application in other climatic conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Acid- and base titration behaviour of finnish mineral soils

The acid- and base-buffering properties of 84 non-calcareous surface soil samples were studied by batch titration with HCI or KOH at a constant ionic strength of I = 0.1. The soil samples were classified according to their pH of zero point of titration (ZPT). Differential buffer values, dB(H) or dB(OH) (H⁺ or OH^? as meq kg^?1 needed to reduce or increase the soil pH sequentially by 0.5 units, respectively), were introduced to describe the course of titration curve and the intensity of buffer action. In all soils, the first acid-buffer value, dB(H)_0→0.5, varied from 8 to 78 meq kg^?1 and the second one, dB(H)_0.5→1, from 10 to 138 meq kg^?1. The corresponding base-buffer values, dB(OH)_0→0.5 and dB(OH)_0.5→1, ranged from 10 to 48 and from 14 to 44 meq kg^?1, respectively. The most acid soils were most strongly buffered against acid, and the soils with the highest initial pH against base. The results reveal the acid-buffering by exchange reactions to be very important. In the soils with ZPT≦5.4, the first acid-buffer value was dependent on the content of organic matter and oxalate-soluble Al, whereas in the more acid soils the role of clay became significant. Thus, it was concluded that at higher pHs the foremost inactivation of H⁺ is attributable to soil components of pH-dependent charges, and the significance of constituents of permanent charges to increase with proceeding acidification. In strongly acid soils (ZPT≦4.8) the very effective buffering seemed to be primarily due to the dissolution of Al-hydroxides and, thus, to exert detrimental effects on the edaphic environment. The general rank of soil factors explaining the variation in the base-buffer values was in accord with the neutralization sequence, i.e. the strongest acid in the soil being neutralized first. In the strongly acid soils (ZPT≦4.8) the base-buffer values seemed to depend on the clay as well as KCl- and NH₄OAc-extractable Al, whereas in the soils with higher initial pH mostly on organic C.     

Characterization of subtropical soils by mineral magnetic measurements

Abstract

This paper reports the use of mineral magnetic measurement techniques to characterize the iron oxide assemblage within soils of varying parent material type and water regime from subtropical region in Zhejiang Province, China. Results show that dryland soils formed on Quaternary red clay, limestone, arenaceous shale, and diluvium, exhibit a distinct ferrimagnetic profile with a magnetic susceptibility (χ) enhancement in surface horizon. This enhancement is interpreted as being due to pedogenic superparamagnetic (SP) ferrimagnetic grains, which is supported by a higher frequency dependent susceptibility (χ_fd) values. The χ and χ_fd have highly significant positive linear relationship with dithionite‐citrate‐bicarbonate (DCB) extractable iron (Fed) content. The upper horizon of paddy soil has extremely lower χ and χ_fd values than dryland soils formed on the same parent material. Soil with poorly‐drained condition has distinctly lower absolute χ and saturation isothermal remanent magnetization (SIRM) value than associated well‐drained soil. It indicates that reduction state is an important factor responsible for loss of SP ferrimagnetic minerals in soils.     

Soil physical properties related to soil structure

The aim of this paper is to clarify the effect of soil aggregation on soil physical and chemical properties of structured soils both on a bulk soil scale, for single aggregates, as well as for homogenized material. Aggregate formation and aggregate strength depend on swelling and shrinkage processes and on biological activity and kinds of organic exudates as well as on the intensity, number and time of swelling and drying events. Such aggregates are, most of all, more dense than the aggregated bulk soil. The intra-aggregate pore distribution consists not only of finer pores but these are also more tortuous. Thus, water fluxes in aggregated soils are mostly multidimensional and the corresponding water fluxes in the intra-aggregate pore system are much smaller. Furthermore, ion transport by mass flow as well as by diffusion are delayed, whereby the length of the flow path in such tortuous finer pores further retards chemical exchange processes. The chemical composition of the percolating soil solution differs even more from that of the corresponding homogenized material the stronger and denser the aggregates are.

The rearrangement of particles by aggregate formation also induces an increased apparent thermal diffusivity as compared with the homogenized material. The aggregate formation also affects the aeration and the gaseous composition of the intra-aggregate pore space. Depending on the kind and intensity of aggregation, the intra-aggregate pores can be completely anoxic, while the inter-aggregate pores are already completely aerated. The higher the amount of dissolved organic carbon in the percolating soil solution, the more pronounced is the difference between the gaseous composition in the inter- and in the intra-aggregate pore system.

From the mechanical point of view, the strength single aggregates, determined as the angle of internal friction and cohesion, depends on the number of contact points or the forces, which can be transmitted at each single contact point. The more structured soils are, the higher the proportion of the effective stress on the total stress is, but even in single aggregates positive pore water pressure values can be revealed. Dynamic forces e.g. due to wheeling and/or slip processes can affect the pore system as well as the composition of the soil by: (1) a rearrangement of single aggregates in the existing inter-aggregate pore system resulting in an increased bulk density and a less aerated and less rootable soil volume, (2) a complete homogenization, i.e. aggregate deterioration due to shearing. Thus, the smaller texture dependent soil strength coincides with a more intensive soil compaction due to loading. (3) Aggregate deterioration due to shearing results in a complete homogenization, if excess soil water is available owing to kneading as soon as the octahedral shear stresses and the mean normal stresses exceed the stress state defined by the Mohr-Coulomb failure line. Consequently, normal shrinkage processes start again.

Thus, the rearrangement of particles and the formation of well defined single aggregates even at the same bulk density of the bulk soil both affect, to a great extent, various ecological parameters. Environmental aspects can also be correlated, or at least explained with the processes in soils, as a major compartment of terrestial ecosystems, if the physical and chemical properties of the structure elements and their composition in the bulk soil are understood.     

Is ‘grey literature’ a reliable source of data to characterize soils at the scale of a region? A case study in a maritime pine forest in southwestern France

Soil scientists are receiving increasing numbers of requests for expert advice on soil over large areas, but at a high resolution. We tested the use of the soil data contained in sources of information that are not directly accessible (referred to as ‘grey’ data) to accomplish this task. We collected grey data about a pine forest, which is currently the subject of drastic, and questionable, changes in management, including a rapid rate of biomass removal. These grey data (from 266 sites) were compared with soil data obtained directly from our field sampling (83 sites). Our comparisons showed that the two sources of data were consistent when the variables concerned had been sampled and analysed by using methods shared by the soil scientists such as particle‐size distribution. Conversely, significant discrepancies appeared for variables for which different methods existed, such as for CEC. For the latter, using corrective equations gave contrasting results, depending on the soil variable. The final database was used to characterize the soils of the study region. Results showed that soils of the study region (mainly sandy podzols and arenosols) were acidic and particularly oligotrophic. Several important properties (CEC, phosphorus cycling, pH, bulk density) were related to the organic fraction or carbon (C) content of soils. For instance, CEC values were linearly and exclusively dependent on C content. The most oligotrophic sites of the study region were clearly not suitable for the new intensive management of the forest in the long term. For the other sites, the question remains open because some specific data are still needed before drawing conclusions. We conclude that as a complement to conventional soil studies, the grey literature is a useful source of data and information to characterize soils at a regional scale.     

山东主要果园土壤的粘土矿物组成及其吸附特性

研究了山东主要果园土壤中粘土矿物的组成、类型及其对P、K和Cu、Zn、Pb金属元素的吸附特性。结果表明：山东主要果园土壤的粘土矿物类型存在着明显的差异,淋溶较强,酸度较大的棕壤（简育湿润淋溶土）中粘土矿物以高岭石占优势,对P的吸附较强,但对K＋吸附固定较弱。含游离C aCO3较高的潮土（淡色潮湿雏形土）和褐土（简育干润淋溶土）,对P有较强的吸附和沉淀作用,使土壤磷的有效性降低。而砂姜黑土（钙积潮湿变性土）由于含有较高的蒙脱石和1.4 nm过渡矿物,对K＋具有很强的吸附和晶穴固定作用,因此砂姜黑土中磷肥和钾肥的有效性均较低,在施肥上应采取集中施肥和保持较湿润土壤环境等措施,以提高养分有效性。砂姜黑土和潮土对Cu、Zn、Pb金属元素的吸附显著地大于棕壤和褐土,主要的影响因素是不同土壤的粘粒含量和粘土矿物的类型的差异。同一土壤对Pb的吸附量远远大于对Zn和Cu的吸附量,主要取决于金属元素本身的化学性质和胶体的吸附特性。     

几种类型土壤中砷环境基准的比较研究

本研究依据我国四种类型土壤中存在过量砷所产生的生态效应与环境效应，确定了砷的的环境基准。分布在东南部的红壤和黄棕壤的基准为４５－５１ｍｇ／ｋｇ，分布在华北的褐土和西北的灰钙土为２１－２５ｍｇ／ｋｇ。     

3种烟碱类杀虫剂在土壤中的降解吸附特性及对地下水的影响

采用室内模拟实验方法,以太湖水稻土、江西红壤和东北黑土为代表性土壤,研究了噻虫啉等3种烟碱类杀虫剂在土壤中的降解、吸附特性,并利用GUS（Ground Ubiquity Score）指数分析了其对地下水污染的影响。结果表明,3种烟碱类杀虫剂在3种土壤中均较易降解,降解半衰期在5～31d之间,属于易降解农药,降解特性与土壤理化性质及农药本身性质有关。3种烟碱类杀虫剂在江西红壤、太湖水稻土与东北黑土中的吸附较好地符合Freundlich方程,Kd值在0.30～14.70之间,KOC在42.8～1750.9之间,属难吸附农药。吸附性强弱与农药本身溶解性和土壤有机质含量有关,水溶性越强吸附越弱,有机质含量越高,吸附性越强。3种烟碱类杀虫剂在太湖水稻土中的GUS值均小于1.8,而在江西红壤中,其GUS值均大于1.8,这3种杀虫剂在江西红壤中均有一定的淋溶性,对地下水均有一定的污染风险。     

Applying a GLM-based approach to model the influence of soil properties on the toxicity of phenmedipham to Folsomia candida

Purpose

Soil properties are the main explanation to the different toxicities obtained in different soils due to their influence on chemical bioavailability and the test species performance itself. However, most prediction studies are centred on a few soil properties influencing bioavailability, while their direct effects on test species performance are usually neglected. In our study, we develop prediction models for the toxicity values obtained in a set of soils taking into account both the chemical concentration and their soil properties.

Materials and methods

The effects on the avoidance behaviour and on reproduction of the herbicide phenmedipham to the collembolan Folsomia candida is assessed in 12 natural soils and the Organisation for Economic Co-operation and Development (OECD) artificial soil. The toxicity outcomes in different soils are compared and explanatory models are constructed by generalised linear models (GLMs) using phenmedipham concentrations and soil properties.

Results and discussion

At identical phenmedipham concentrations, the effects on reproduction and the avoidance response observed in OECD soil were similar to those observed in natural soils, while effects on survival were clearly lower in this soil. The organic matter and silt content explained differences in the avoidance behaviour in different soils; for reproduction, there was a more complex pattern involving several soil properties.

Conclusions

Our results highlight the need for approaches taking into account all the soil properties as a whole, as a necessary step to improve the prediction of the toxicity of particular chemicals to any particular soil.     

Soil reflectance as a generic tool for assessing infiltration rate induced by structural crust for heterogeneous soils

Raindrop energy disintegrates soil aggregates and rearranges soil particles to form a structural crust on the upper soil layer. The structural crust affects the physical properties of the soil, which can be observed by significant colour changes on the soil surface. Spectral differences observed in the structural crust are caused by rearrangement of the soil surface texture, mainly an increase in the clay fraction. Previous studies conducted on crusted soils using reflectance spectroscopy were limited to a certain soil type or area and seemed to be strongly dependent on the small range of soil types. In the current study, the influence of raindrop energy on the NIR‐SWIR spectral reflectance (1200–2400 nm) of heterogeneous soils was evaluated and used in combination with partial least squares (PLS) regression to construct a model that correlates the infiltration rate (IR) with its reflectance. Four soils from Israel and three soils from the USA were studied to provide a single data set. A relatively small root mean square error of cross‐validation (RMSECV) of 15.2% was found. A ratio of prediction to deviation (RPD) value of 1.98 indicates a promising generic model. Additionally, PLS models were run on different combinations of soil types (RPD values ranging between 2.4 and 3.2). For all models, whether all soils were run in one cross‐validation data set, or run for different combinations of soils, the best assessment of IR was achieved when using reduced wavelength range (selected wavelengths based on Martens’ significance test selection). These results allowed us to conclude that a generic approach aimed at assessing the structural crust for a variety of soils is feasible. A generic model using the suggested spectral approach has the potential to provide NIR‐SWIR spectral soil IR predictions with either a local or global data base of soils worldwide and may contribute to improved protection of crusted soils from erosion or water loss by runoff.