Comparative studies and assessment of the particle-size distribution in soils of Lithuania by the Kachinskii and FAO methods

The particle-size distribution was analyzed by the Kachinskii and FAO methods in 564 samples collected from 131 soil profiles. Scaling factors are given for converting the data obtained by the Kachinskii method into the FAO method, and the relationship between the particle-size fractions determined by the FAO (y) and Kachinskii (x) methods is presented in the form of a regression equation. It is found that the difference in the data obtained by both methods is controlled not only by the soil texture (sand, sandy loam, loam, etc.) but also by the genesis of the soil-forming deposits, as well as by the amount of humus and carbonates in them.     

Spatial variability in the distribution of particle-size fractions in agrogray soils and agrogray soils with the second humus horizon

The degree of spatial variability in the distribution of particle-size fractions has been determined for agrogray soils of an experimental field of Bryansk Agricultural Academy. The degree of spatial variability is close to the analytical error; for comparing different plots, particle-size distribution analysis has to be performed in two-three replicates. If the particular sets of data (e.g., data sets on the content of clay in the upper and lower parts of the plow horizon) are used, the statistical probability of differences increases. Cluster analysis can be used for the initial grouping of particle-size distribution data.     

Effect of the particle-size distribution on the adsorption of copper, lead, and zinc by Chernozemic soils of Rostov oblast

The parameters of adsorption of Cu²⁺, Pb²⁺, and Zn²⁺ cations by soils and their particle-size fractions were studied. The adsorption of metals by soils and the strength of their fixation on the surface of soil particles under both mono- and polyelement contamination decreased with the decreasing proportion of fine fractions in the soil. The adsorption capacity of the Lower Don chernozems for Cu²⁺, Pb²⁺, and Zn²⁺ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem ∼ clay loamy southern chernozem > loamy southern chernozem > loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions (C _max and k), the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu²⁺ ≥ Pb²⁺ > Zn²⁺. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem > loamy chernozem > loamy sandy chernozem. The analysis of the changes in the parameters of the Cu²⁺, Pb²⁺, and Zn²⁺ adsorption by soils and their particlesize fractions showed that the extensive adsorption characteristic, namely, the maximum adsorption (C _max), was a less sensitive parameter characterizing the soil than the intensive characteristic of the process—the adsorption equilibrium constant (k).     

The classification, distribution, and extent of soils with a xeric moisture regime in the United States

Soils with cool, moist winters and relatively warm, dry summers, a Mediterranean climate, are recognized as having a xeric moisture regime in Soil Taxonomy. These soils are classified mostly in taxa that use the formative element “xer” in the name. Soil series with either a xeric moisture regime or an aridic regime bordering on a xeric moisture regime make up more than 48,640,000 hectares in the western part of the United States. They are classified in the orders of Mollisols (20,080,000 ha), Aridisols (11,200,000 ha), Alfisols (5,320,000 ha), Inceptisols (4,800,000 ha), Entisols (4,400,000 ha), Vertisols (1,520,000 ha), Andisols (960,000 ha), and Ultisols (960,000 ha).     

The effect of organic matter on the difference between particle-size distribution data obtained by the sedimentometric and laser diffraction methods

Particle-size distribution in dispersed sediments, soils, atmospheric dust, and other natural objects is their fundamental characteristic. The methods of sedimentometry (the pipette method) and laser diffraction have been applied to study particle-size distribution in a typical chernozem of Kursk oblast from the Alekhin Central Chernozemic Reserve. The content of the clay fraction as determined by the method of laser diffraction is three to five times lower than the clay content determined by the traditional pipette method. One of the reasons for such a great difference in the results obtained by two different methods is related to the low density of the solid phase of the particles of soil organic matter that have the size corresponding to the fine and medium silt fractions. Owing to this, they fall into the category of the clay fraction during the traditional sedimentometric analysis. The initially water-stable aggregates of 0.25–0.5 mm in size are subjected to several stages of their breakdown under the impact of ultrasonic dispersion with the detachment of small particles from their surface layers. The remaining aggregates have different resistance to ultrasonic treatment. After the long-term ultrasonic dispersion, the most stable microaggregates still exist in the soil mass. These microaggregates may only be decomposed to elementary soil particles after the addition of sodium pyrophosphate.     

雷州半岛玄武岩母质土壤剖面稀土元素分布及其与常量元素、粒度的关系

对雷州半岛玄武岩母质土壤剖面稀土元素地球化学特征进行了研究,结果表明:土壤剖面中稀土元素的分布既受母岩的控制,又叠加了风化成壤作用的影响,∑REE和δEu对母岩有明显的继承性,风化成壤作用则导致REE在剖面上部富集以及土壤中Ce的显著正异常,并造成轻、重稀土之间发生一定的分馏(以轻稀土富集为主要特征),但轻稀土或重稀土内部未出现明显的分异;∑REE与Fe2O3含量呈极显著负相关,可能与风化成土过程中铁氧化物结晶程度提高,富含REE的无定形铁含量降低有关;∑REE与P2O5、MnO则呈极显著正相关,应当是由于剖面中含有较多的赋存REE的磷酸盐矿物和锰氧化物矿物所致;∑REE与黏粒组分(尤其是<1μm的组分)呈极显著正相关,表明风化成壤过程中黏土矿物含量增加所导致的对REE的吸附效应是造成该区REE富集的重要原因,其中黏粒对轻稀土元素的吸附更为明显。     

草原土壤：分布、分类与演化

草原土壤系指草原、湿草原和森林草原植被下形成的富含有机质、盐基饱和度高的暗色土壤.世界上此类土壤面积约900万km2,我国约76万km2,是粮食生产的重要基地.本文比较了国际上草原土壤分类.不论俄罗斯或中国,均腐土开垦以后土壤有机质开始下降迅速,而后减缓,逐步达到与当地生物气候相适应的水平.所以至今仍保持一定厚度的黑土层.在均腐土资源的利用和保护上,一方面应保持其有机质平衡,另一方面更重要的是严防水土流失,以保证其生产能力.     

Influence of tillage and rotation systems on distribution of organic carbon associated with particle-size fractions in Chernozemic soils of Saskatchewan, Canada

The effects of several dominant tillage and rotation systems on soil organic C content of different particle-size fractions were studied in Chernozemic soils from southwestern and east-central Saskatchewan, Canada. In an Orthic Brown Chernozem in southwestern Saskatchewan, 7 years of no-till cereal–fallow, imposed on a long-term tillage fallow–wheat rotation soil, resulted in 0.1 Mg C ha⁻¹ more organic C mass in the sand + organic matter (OM) fraction of the 0- to 5-cm layer, whereas organic C associated with coarse silt (CS), fine silt (FS), coarse clay, and fine clay of 0- to 5- and 5- to 10-cm layers was less than that of the comparable tilled cereal–fallow system. Conversion of tilled fallow–wheat rotation soil to continuous cropping had a slight effect, whereas the organic C mass in all the size fractions was significantly increased in both 0- to 5- and 5- to 10-cm layers after alfalfa was introduced on tilled fallow–wheat as perennial forage for 10 years. In an Orthic Black Chernozem in east-central Saskatchewan that was cultivated and tilled using a cereal–fallow rotation for 62 years, organic C mass decreased in sand + OM, CS, and FS of 0- to 10-cm depth. Conversion of the tilled cereal–fallow cropland soil back to seeded grassland resulted in significantly more soil organic C in sand + OM fraction after 12 years of grass seed-down. The sand + OM fraction appears to be the size fraction pool initially most sensitive to adoption of management practices that are liable to sequester carbon in the soil.     

A new classification system of soils of Russia: Preliminary results of discussion

The first version of the profile-genetic classification system of the soils of Russia published in 1997 was discussed by soil scientists and verified in different ways. As a result, a number of changes and additions were made in the new version of 2004. Many comments concerning this version were obtained from the regional divisions of the Dokuchaev Society of Soil Scientists, as well as from specialists (papers in Eurasian Soil Science and discussion on the Internet). The authors of the classification system consider it reasonable to analyze the results of the discussion concerning both the principles and nomenclature and some groups of soils.     

Effect of particle-size distribution, soil organic carbon content and organo-mineral aluminium complexes on acid phosphatases of seasonally flooded forest soils

We studied the acid phosphatase activity (APA) and its relationships with some soil physico-chemical properties along a seasonally flooded forest gradient. The soil samples were collected during the non-flooded period in three zones subjected to different flooding periods: a zone inundated 8 months per year (MAX), a zone inundated 5 months per year (MED), and a zone inundated 2 months per year (MIN). In the MAX zone APA was low and negatively correlated with the fine earth fraction of soil. In this zone, clay minerals appeared to reduce the enzymatic activity. In the MIN zone acid phosphatase had a relatively higher activity, which was positively correlated with the soil organic C content and with Al associated with the organic matter. The highest value of APA was obtained in the MED zone, and no correlation was found between edaphic factors and the enzymatic activity in this zone. However our results are restricted to a single sampling date and, therefore, they do not take into account the seasonal dynamics of acid phosphatase in relation to other soil factors over time.     

The WEELS model: methods, results and limitations

Within the European Union (EU)-funded Project ‘Wind Erosion on European Light Soils’ (WEELS), a model was designed and implemented with the aim of predicting the long-term spatial distribution of wind erosion risks in terms of erosion hours and wind-induced soil loss. In order to ensure wide applicability, the model structure consists of a modular combination of different approaches and algorithms, running on available or easily collected topographic and climatological data input. Whereas the ‘WIND’, ‘WIND EROSIVITY’ and ‘SOIL MOISTURE’ modules combine factors that contribute to the temporal variations of climatic erosivity, the ‘SOIL ERODIBILITY’, ‘SURFACE ROUGHNESS’ and ‘LAND USE’ modules predict the temporal soil and vegetation cover variables that control soil erodibility. Preliminary simulations over a 29-year period for the Barnham site (UK) (1970–1998) and a 13-year period for the Grönheim site (Germany) (1981–1993) generally resulted in a higher erosion risk for the English test site, where the total mean soil loss was estimated at 1.56 t ha⁻¹ year⁻¹ and mean maximum soil loss at about 15.5 t ha⁻¹ year⁻¹. The highest rates exceeded 3 t ha⁻¹ in March, September and November. On the northern German test site, the total mean soil loss was 0.43 t ha⁻¹ year⁻¹. The highest erosion rates were predicted in April when they can exceed 2.5 t ha⁻¹. The total mean maximum soil loss at this site of about 10.0 t ha⁻¹ year⁻¹ corresponds to a loss of about 0.65 mm. Predictions based on a land use scenario for the German site revealed that the erosion risk could be reduced significantly by changing land use strategies.     

Distribution of the particle-size fractions in soddy-podzolic soils subjected to sheet erosion

Tendencies in the formation of organomineral profiles of arable agrosoddy-podzolic soils on slopes in different denudation and accumulation zones were characterized on the basis of an integrated study of the humus status of the soils (using the granulodensimetric fractionation method), the content of clay, and the composition of clay minerals. It was shown that the organomineral and mineralogical parameters of the surface-horizon transformation could be used for improving the diagnostic accuracy of soils on the slopes basing on their conventional characteristics.     

Extractable lipid contents and colour in particle-size separates and bulk arable soils

Chemical alteration of plant biomass to soil organic matter is often accompanied by characteristic trends, e.g. with decreasing particle size and increasing depth organic carbon and nitrogen concentrations and stable carbon isotope values (δ¹³C) often increase. In agricultural soils, systematic studies of soil organic carbon (SOC) distribution in bulk soils and particle‐size separates of depth profiles are scarce. In this study, three soil profiles from one site with different monoculture crops were analysed for organic carbon and nitrogen concentrations, stable carbon isotopes, bulk extractable lipids, and soil colour. In contrast to most previous observations, stable carbon isotope values were constant over soil depth and within particle‐size separates, probably as a result of little biomass input due to the harvesting techniques applied and the presence of fossil carbon. Bulk extractable lipids contributed 1–10% to the total SOC. Significantly more lipids could be extracted from rye‐ than from maize‐derived SOC. Lipid yields normalized to soil mass increased with decreasing particle size and decreased with depth. When normalized to organic carbon concentration, sand‐size fractions had the largest lipid yields. Soil colour, expressed as Munsell values, was lightest in sand‐ and silt‐size separates. A cross‐plot of Munsell values and their SOC concentrations revealed characteristic, non‐overlapping areas for each particle‐size class and the bulk soils. Clay‐size separates and bulk soils were almost identical in Munsell values, although for clay‐size separates SOC concentrations were much larger than for bulk soils. Thus, the SOC‐rich clay‐size separates exerted the dominant influence on the colour of the bulk soils. Determination of colour and extractable lipid contents could be useful additional parameters for soil characterization.     

Peat soils: Genesis and classification

This paper considers three topical problems—the definition of peat soils as natural-historical formations and the estimation of their profile thickness, the analysis of the genesis of organic soils, and the principles of the classification of peat soils. Based on the experimental data of long-term studies, it was concluded that peat soils may include the whole peat layer and the upper horizons of the surface mineral soil. The organic and mineral parts of the natural structures were found to be a genetically homogeneous soil profile, which has the same history of development. The upper layer of the peat soils should be considered as the horizon reflecting the contemporary stage of the soil formation. A hierarchy of peat soils is analyzed for developing their classification.     

Pore-size distribution in loamy soils: A comparison between microtomographic and capillarimetric determination methods

Pore-size distribution in a soddy-podzolic silt loamy soil developing from mantle loesslike loam (Eutric Albic Retisol (Loamic, Cutanic)) was calculated from the water retention curve according to Jurin’s equation and directly determined in microtomographic experiments. Rounded macropores with the diameter of their sections from 75 to 1000 μm predominate in horizontal sections if the studied soil samples. A larger part of the soil pores (>30–35%) belongs to micro- and nanopores, and they cannot be quantitatively determined by the tomographic method, because their sizes are smaller than the detection limit of the applied X-ray microtomography (8.75 μm per pixel). This leads to a significantly larger pore volume determined from the water retention curve in comparison with the “tomographic” pore volume. A comparative analysis of pore-size distribution curves obtained by these methods shows that the major regularities of the pore-size distribution in the range from 30 to 5000 μm are similar in both cases. Fine macropores and, partly, mesopores predominate. Common characteristics of the pore-size distribution curves obtained by these methods, including the coincidence of the peaks, attest to the validity of classical approaches, according to which the hydrology of soil pore space can be perceived as a physical model of cylindrical capillaries of different sizes with capillary-sorbed water.     

Exploring the enzymatic landscape: distribution and kinetics of hydrolytic enzymes in soil particle-size fractions

The location of extracellular enzymes within the soil architecture and their association with the various soil components affects their catalytic potential. A soil fractionation study was carried out to investigate: (a) the distribution of a range of hydrolytic enzymes involved in C, N and P transformations, (b) the effect of the location on their respective kinetics, (c) the effect of long-term N fertilizer management on enzyme distribution and kinetic parameters. Soil (silty clay loam) from grassland which had received 0 or 200 kg N ha⁻¹ yr⁻¹ was fractionated, and four particle-size fractions (>200, 200-63, 63-2 and 0.1-2 μm) were obtained by a combination of wet-sieving and centrifugation, after low-energy ultrasonication. All fractions were assayed for four carbohydrases (β-cellobiohydrolase, N-acetyl-β-glucosaminidase, β-glucosidase and β-xylosidase), acid phosphatase and leucine-aminopeptidase using a microplate fluorimetric assay based on MUB-substrates. Enzyme kinetics (V_max and K_m) were estimated in three particle-size fractions and the unfractionated soil. The results showed that not all particle-size fractions were equally enzymatically active and that the distribution of enzymes between fractions depended on the enzyme. Carbohydrases predominated in the coarser fractions while phosphatase and leucine-aminopeptidase were predominant in the clay-size fraction. The Michaelis constant (K_m) varied among fractions, indicating that the association of the same enzyme with different particle-size fractions affected its substrate affinity. The same values of K_m were found in the same fractions from the soil under two contrasting fertilizer management regimes, indicating that the Michaelis constant was unaffected by soil changes caused by N fertilizer management.     

The basaltic soils of SE Nigeria: properties, classification and constraints to productivity

Four basaltic profiles located in northern Cross River State of Nigeria are described and characterized. The soils are classified as Typic Tropohumult and show strong acidity, low effective CEC, low N and available P. Organic matter levels of the surface soils are high. All the soils are well drained in spite of high YO clay, which is apparently kaolinitic, with moderate to high A1 saturation. Higher agricultural productivity of these soils is restricted by low effective CEC and strong acidity. Measures to combat these problems are suggested.