我国几种土壤铁锰结核中的锰矿物类型

用Ｘ－射线衍射和化学选择溶提技术研究我国几种土壤中铁锰结核的锰矿物类型的结果表明：供试土壤铁锰结核都含有锂硬锰矿,除山东钙积潮湿变性以钙锰矿占优势外,其它样品中的锰矿物均以锂硬锰矿为主,结晶程度较高;湖北武汉和枣阳的粘磐湿润淋溶土的铁锰结核含有钠水锰矿和羟水锰矿;湖南宜章富铝湿润富铁土、湖北枣磐湿润淋溶土和山东钙积潮湿变性土的铁锰结核中的有钡硬锰矿;湖南桂阳富铝湿润富铁土的铁锰结核中检测出少量的铅     

Self-repair of compacted Vertisols from Central Queensland, Australia

Vertisols have the inherent ability to self-repair because of high clay contents and clay type that govern volume change. A study was undertaken to correlate soil inherent properties with two indicators of structure improvement based on tensile strength and clod porosity of compacted soil cores before and after wet/dry cycles. In order to minimize inter-soil differences Vertisols under similar cropping regimes and from the same climatic region in Queensland, Australia were selected. A soil repair index (R_T(1)) based on compressive strength of soil cores was related to soil inherent properties and shrinkage indices, COLE_STD and LS_MOD using multiple regression. Results showed that compressive strength of soil cores after a single wet/dry cycle after compaction was sufficient to rank Vertisols in terms of their capacity to improve structure after compaction. Clay content and clay activity (CEC/clay) on their own were poor indicators of soil repair. Fine sand was shown to be an important component in the repair process. LS_MOD and COLE_STD predicted R_T(1) equally well and indicated that Vertisols with COLE_STD values > 0.15 and LS_MOD > 12% would be expected to have sharper reductions in tensile strength compared to those with lower values after just one wet/dry cycle. Clod porosity was poorly related to soil inherent properties.     

Soil formation in Greyzems in Moscow district: micromorphology, chemistry, clay mineralogy and particle size distribution

Greyzems (Grey Forest Soils) are zonal soils of the forest–steppe, in Russia geographically situated between the (Podzo) Luvisols of the southern taiga forest and the (Luvic) Chernozems of the steppe. Greyzems are characterized by a dark mollic horizon, with uncoated (bleached) silt and sand grains on pedfaces, and an argic horizon as diagnostic horizons. The FAO–Unesco soil map of the world shows Greyzems and Luvisols in Russia at this transition (the Russian soil map shows only Greyzems), while in similar geographic position in the USA and Canada the proportion of Greyzems is very small and Luvic Phaeozems/Chernozems and Albic Luvisols occupy those transitional zones of the grassland–forest interface. Three Greyzem profiles, presently under forest, and developed on loess-like mantle loams of Late Weichselian (Valday) age in the northern forest–steppe zone of the East European plain (Middle Russian Upland) were described and sampled near Pushchino, some 100 km south of Moscow. Micromorphology, particle size data, chemical data and clay mineralogy were studied. Based on the particle size distribution and the occurrence of fragments of a second humus horizon (SHH) the presence of two, rather similar, deposits in the solum is advocated. The following processes have been deduced from the study: (i) decalcification and secondary accumulation of carbonates; (ii) humus accumulation, including the significance of the SHH; (iii) clay illuviation, presumably two main phases; (iv) biological activity; (v) degradation of the mollic A: occurrence of bleached grains; (vi) downward migration of textural components and organic matter, in the Bt horizon along major pedfaces: occurrence of black organo-clay coatings and uncoated silt/sand grains; (vii) gleying. The tentative sequence of these processes during Late Weichselian and Holocene times leads us to conclude that Greyzems are polygenetic. They formed as Podzo(Luvisols) under forest, with fine clay coatings in the fine pores inside the blocky and prismatic peds, in the Late Glacial and Early Holocene. The change to tall grass steppe in the Atlanticum created a mollic horizon, that degrades when forest re-invades during the Subatlanticum. Fine clay, combined with organic matter forms black coatings on the major pedfaces. Uncoated silt and sand particles also migrate downward along those major pedfaces. Biological activity is involved in the very complex pattern of the transitional AhE and EBt horizons. Active gleying only occurs in the profile on the lowest topographic position. These latter processes are still active today. Similar soils do occur in the grassland–forest interface in North America, except where the younger age of the landscape and high CaCO3 content at shallow depth prevented their full development.     

Soil–landscape variability: mapping and building detail information for soil management

The study of soil–landscape relationships at a detailed scale (1:10 000) and its use for soil management was less common in developing countries. The study was conducted in western Ethiopia with the aim to explain the soil variability across landscapes, classify soils into mapping units and produce a map of these soils. This study was performed based on a discrete model of spatial variation. Five soil reference groups: Vertisols, Cambisols, Fluvisols, Luvisols and Leptosols were identified in the study site. Distribution of the soil reference groups was determined by landscape position. Variation in soil texture, colour, pH , exchangeable acidity, organic carbon, total nitrogen, available phosphorus (av. P), carbon to nitrogen ratio (C/N), exchangeable potassium (K), calcium (Ca), magnesium (Mg), sodium (Na) and cation exchange capacity (CEC ) was observed within and among soil mapping units (SMU s). Variability was considerably high for exchangeable Ca and CEC . Factor analysis result indicated that variation in soil properties within land unit was comparatively highest in Leptosols of SMU 9 (88.87%) and lowest in Vertisols of SMU 1 (60.82%). Moderate‐to‐fine scale mapping of soil properties helps to build detail information for soil management. Grouping fields into mapping units that require more or less similar management measure would be an important soil–landscape concept. As a result, mapping units could be used as cost‐effective means of treating variable field so as to optimize the forecasted benefits.     

Chernozem—Soil of the Year 2005

The proclamation of the “Soil of the Year” was made for the first time in Germany in 2005 on occasion of the World Soil Day. Chernozems were selected for this purpose. In this paper an overview of these groups of soils is given. Chernozems are concentrated in the drought region of Central Germany. A standard profile from the core area of Chernozems developed from loess is presented with comprehensive laboratory analysis. Chernozems developed primarily upon carbonatic loess substrates under summer‐dry climatic conditions in an open park‐like landscape with isolated forest stands. The development of Chernozems began as early as the late glacial period, and they were fully developed by the Atlantikum age. The far‐reaching, uniformly thick humus horizons indicate substrate differences in the loess cover, which are partly the result of bioturbation. Within Germany, Chernozems and Chernozem‐like soils make up approx. 3% of the surface area and 5% (approx. 11,000 km²) of the arable land. The results of the Static Fertilization Experiment in Bad Lauchstädt, founded in 1902, clarify the high value of Chernozem for biomass production and the environment. Each loss due to erosion or decrease in surface area reduces the fulfillment of soil ecological functions of the soils and is comparable to a loss of animal and plant species. Therefore, soil scientists and the results of soil research must be more comprehensively implemented for soil preservation, protection, and politics. For acceptance of these goals among the general public and the political‐decision makers, the campaign “Soil of the Year” should give some thought‐provoking impulses.     

Effect of soil compaction on hydraulic properties of two loess soils in China

Soil compaction affects hydraulic properties, and thus can lead to soil degradation and other adverse effects on environmental quality. This study evaluates the effects of three levels of compaction on the hydraulic properties of two silty loam soils from the Loess Plateau, China. Undisturbed soil cores were collected from the surface (0–5 cm) and subsurface (10–15 cm) layers at sites in Mizhi and Heyang in Shaanxi Province. The three levels of soil compaction were set by increasing soil bulk density by 0% (C0), 10% (C1) and 20% (C2) through compression and hammering in the laboratory. Soil water retention curves were then determined, and both saturated hydraulic conductivity (K_s) and unsaturated hydraulic conductivity were estimated for all of the samples using standard suction apparatus, a constant head method and the hot-air method, respectively. The high level of compaction (C2) significantly changed the water retention curves of both the surface and subsurface layers of the Heyang soil, and both levels of compaction (C1 and C2) changed the curves of the two layers from the Mizhi site. However, the effects of compaction on the two soils were only pronounced below water tensions of 100 kPa. Saturated hydraulic conductivities (K_s) were significantly reduced by the highest compaction level for both sampled layers of the Heyang soil, but no difference was observed in this respect between the C0 and C1 treatments. K_s values decreased with increasing soil compaction for both layers of the Mizhi soil. Unsaturated hydraulic conductivities were not affected by soil compaction levels in the measured water volume ratio range, and the values obtained were two to five orders of magnitude higher for the Mizhi soil than for the Heyang soil. The results indicate that soil compaction could strongly influence, in different ways, the hydraulic properties of the two soils.     

Review of modelling crop growth, movement of water and chemicals in relation to topsoil and subsoil compaction

Soil compaction influences crop growth, movement of water and chemicals in numerous ways. Mathematical modelling contributes to better understanding of the complex and variable effects. This paper reviews models for simulating topsoil and subsoil compaction effects. The need for including both topsoil and subsoil compaction results from still increasing compactive effect of vehicular pressure which penetrates more and more into the subsoil and which is very persistent. The models vary widely in their conceptual approach, degree of complexity, input parameters and output presentation. Mechanistic and deterministic models were most frequently used. To characterise soil compactness, the models use bulk density and/or penetration resistance and water content data. In most models root growth is predicted as a function of mechanical impedance and water status of soil and crop yield—from interactions of soil water and plant transpiration and assimilation. Models for predicting movement of water and chemicals are based on the Darcy/Richards one-dimensional flow equation. The effect of soil compaction is considered by changing hydraulic conductivity, water retention and root growth. The models available allow assessment of the effects of topsoil and subsoil compaction on crop yield, vertical root distribution, chemical movement and soil erosion. The performance of some models was improved by considering macro-porosity and strength discontinuity (spatial and temporal variability of material parameters). Scarcity of experimental data on the heterogeneity is a constraint in modelling the effects of soil compaction. Suitability of most models was determined under given site conditions. Few of the models (i.e. SIBIL and SIMWASER) were found to be satisfactory in modelling the effect of soil compaction on soil water dynamics and crop growth under different climate and soil conditions.     

我国一些主要土壤铁锰结核中氧化锰矿的矿物学特征

X－ray diffraction and selective chemical dissolution methods were used to investigate the composition of Mn oxide minerals in Fe-Mn nodules of several main types of soils in China.The changes of relative intensity of X-ray diffraction patterns were studied both before and after chemically selective dissolution.It was found that lithiophorite was a common Mn oxide in all examined Fe-Mn nodules.Todorokite,however,was a predominant Mn oxide in Fe-Mn nodules ,Todorokite,however,was a predominant Mn oxide in Fe-Mn nodules in cal-aquic vertisols of Linyi,Shandong Province,The Fe-Mn nodules of arp-udic Luvisols in Wuhan and Zaoyang,Hubei Province,contained birnessite and vernadite. Hollandite was found in Fe-Mn nodules of alt-udic Ferrisols of Yizhang,Hunan Province,;arp-udic Luvisols of Zaoyang,Hubei Province,and cal-aquic Vertisols of Linyi,Shandong province,The Fe-Mn nodules in alt-udic Ferrisols of Guiyang,Hunan Province,had a few coronadites.Mineralogy of Mn oxide minerals in soil Fe-Mn nodules was related to soil environment,soil types and quantities of relevant cations     

Bulk density by Proctor test as a function of texture for agricultural soils in Maputo province of Mozambique

Soil degradation processes may be of various kinds, including soil compaction. The present study was carried out with the objective of assessing the sensitivity of agricultural or recently abandoned soils in Maputo province of Mozambique to compaction. The assessment is based on the maximum of bulk density attained using the Proctor test (MBD).

In this study the soil texture is expressed by silt plus clay (S + C) or clay (C). The relations between the soil texture and MBD, and between soil texture and critical water content (CWC—soil water at which MBD is attained) were determined. Selected soils range from 10 to 74% of S + C and 9 to 60% of C.

The results suggest there is a relationship between the considered parameters, being that between S + C and MBD or CWC, the best. For MBD the relationship is represented by two quadratic equations with the boundary in between these being a S + C value of 25% and C value of 20%.

Based on the obtained results, one can conclude that the selected parameters may be a useful basis for estimation of the sensitivity to compaction of the Maputo province's soils. It is recommended that similar studies be carried out for soils under forest land and for soil of other provinces to establish the national physical degradation hazard as a function of soil parameters determined routinely and at low cost. The suggested parameters are texture and soil organic matter (SOM).     

Impact of traditional soil burning (guie) on Planosol properties and land‐use intensification in south‐western Ethiopia

In the Gilgel Gibe catchment in Ethiopia, local farmers intensify land use on Planosols by adjusting a traditional soil burning practice known as guie. The burning practice used to be applied in a cycle of shifting cultivation. However, more recently, farmers burn small plots to make fertile seedbeds for Eucalyptus seedlings in the first year before these trees are transplanted to larger plots. The purpose of this research was to assess the physico‐chemical properties of Planosols that have been subjected to burning over the last 10 yrs and evaluate the contribution of guie to land‐use intensification of these soils. Transect studies and interviews of local farmers, followed by chemical, physical and micromorphological analyses of samples from selected plots were used to compare the soil properties of recently (0–2 yrs) and formerly (3–10 yrs) burnt Planosols with those of unburnt Planosols. The analytical results show that the burning practice improved nutrient availability in the first 2 yrs after guie. Increased amounts of exchangeable aluminium (Al) were reported in the long term. Charge fingerprints illustrate that the nutrient‐buffering capacity of the soil was high shortly after the practice but subsequently decreased with time. Given the population pressure on the formerly extensively used Planosols, it is argued that the current application of guie on small, localized plots for raising Eucalyptus seedlings is well adapted to the local socio‐economic context and promotes land‐use intensification on the Planosols. The increased exchangeable Al content of former Eucalyptus seedbeds merits further in‐depth research into the biophysical sustainability of the burning practice.     

Determinants of the degradation of soil structure in vineyards with a view to conversion to organic farming

In perennial crops such as grapevine, there is a considerable risk of soil degradation caused by mechanization. Organic farming may increase traffic and result in more intensive soil structure degradation, especially on wet soil. Soil structure was observed in 69 soil profiles from 12 vineyards (Languedoc‐Roussillon, Bordeaux, Provence, Burgundy, Rhône Valley) to study the relationships between permanent soil characteristics (texture, stoniness, waterlogging), cultivation practices (technical operations, traffic, farm equipment) and soil structure. Compaction zones were identified in soil profiles viewed perpendicularly to the grapevine rows. The percentage of compacted area and a score for compaction intensity were assessed in the top 0.5 m of the soil profile in three soil compartments defined by the distance from the grapevine row: (1) 0 to 0.2 m (2) 0.2 m to 0.5 m and (3) 0.5 m to the middle of the inter‐row. Most soil profiles exhibited considerable compaction: 75% of the soil profiles were compacted in compartments 2 or 3. Intensity correlated with depth of compaction in compartment 2 – the deeper the compaction, the greater the compaction intensity. Four types of soil profiles could be identified, depending on the location of compacted zones and of their intensity of compaction. The factors that determined the types of soil profiles were as follows: soil vulnerability to compaction, use of moderating practices (practices that limit the risk of compaction) and traffic geometry. A statistical analysis resulted in a decision tree that provides a useful basis to choose cultivation practices that limit damage to or improve soil structure.     

我国土壤放射性碳年龄

我国地域辽阔 ,土壤类型众多。土壤中不仅含有有机质和腐殖质 ,而且许多土壤中还含有丰富的钙质结核、分散碳酸盐以及贝壳、珊瑚等可供放射性碳断代的良好对象。土壤有机和无机1 4 C年龄研究表明 ,我国大多数土壤是全新世时期的产物。其中又以全新世中期和晚期的土壤占绝对优势。人为土纲中的土壤年龄与六千余年来我国悠久的农业耕种历史密切相关。相比之下 ,只有少数土壤形成于晚更新世晚期。而另一些土壤有数个形成、发育阶段 ,它们的年龄自然亦就跨越不同的地质时期 ,具有多元化的特点。     

Soil compaction: identification directly in the field

The compaction of soil alters its structure, increases its bulk density and decreases its porosity. These changes can be detected by careful and systematic visual and tactile examination directly in the field. These changes also reduce the permeability of soil to water and air and may alter the pattern of root growth. Further signs of compaction may be induced such as the creation of waterlogged zones or of dry zones caused by shallow rooting denying access to deeper reserves of water. Furthermore, there may be a reduction in nutrient uptake from dry soil. Under wet conditions anoxic pockets may form with associated biochemical changes, some of which are visible. Changes in mineral nitrogen may take place through denitrification and a reduction in nitrification. The criteria used to identify compaction in the field include patterns of crop growth, pale leaf colours, waterlogging on the surface or in subsurface layers above compaction, an increase in soil strength, changes to soil structure, soil colour and the distribution of roots and of soil moisture. Manifestation of soil compaction in crops is also dependent on the weather and is influenced by crop type and variety, and stage of growth. Many soil‐borne diseases are made worse by stress to the crop which might be induced by compaction caused by drier or wetter conditions in the root zone. Where, when and how to identify compaction in the field are discussed and the techniques used are described. Specific examples of the identification of compaction are given, covering a wide range of situations.     

Tillage systems for the West African Semi-Arid Tropics

The West African Semi-Arid Tropics (WASAT) is characterized by a monomodal rainfall pattern, and based on the amount of annual rainfall it can be divided into three ecologies: Sahel, Sudan and Northern Guinea savannahs. The major soil groups of the WASAT are Alfisols, Inceptisols and Entisols and Vertisols, with the former three predominating. The major soil constraints to crop growth are: soil compaction, low fertility, high temperature and low soil water retention, available water holding capacity and infiltration rate. Tillage in traditional farming systems is manual. However, mechanization of tillage operations has received emphasis in the recent past. The accelerated soil degradation which is a feature of mechanized-tillage systems under rainfed agriculture can be minimized with no tillage. However, lower yield have been reported to occur with no tillage. Some possible reasons are: the absence or low amounts of residue mulch, high soil compaction, the presence of harmful soil insects in crop residues, the creation of stable pores by tillage in soils of high organic matter, silt and fine sand contents. Unavailability of crop residues in a major impediment to the adoption of no tillage. The use of heavy and intensive mechanical tillage in irrigated agriculture leads to the formation of plow soles. Deep tillage such as subsoiling does not ensure the elimination of plow soles. While no tillage appears to hold promise for use in the irrigated agriculture of the WASAT much research remains to be done.     

Mechanisms of soil vulnerability to compaction of homogenized and recompacted Ultisols

Soil compaction is a main cause of soil degradation in the world and the information of soil compaction in subtropical China is limited. Three main Ultisols (quaternary red clay, sandstone and granite) in subtropical China were homogenized to pass through 2 mm sieve and recompacted into soil cores at two bulk densities (1.25 and 1.45 g cm⁻³). The soil cores were equilibrated at different matric potential values (−3, −6 and −30 kPa) before subjected to multi-step compaction tests. Objectives of this study were to determine how different initial soil conditions and loading time intervals influence pre-compression stress and to evaluate an easy measure to determine soil vulnerability to compaction. It became evident that the soil strength indicator, pre-compression stress, was affected by soil texture, initial soil bulk density and matric potential. The coarser the soil texture, the lower the bulk density and the higher the matric potential, the lower was the pre-compression stress. The pre-compression stress decreased exponentially with increasing initial soil water content. Soil water content and air permeability decreased after compaction. The amount of water loss was affected not only by soil texture, bulk density and initial water content but also by loading time interval. These results indicate soil pore structure and hydraulic conductivity changed during compactions. The applied stress corresponding to the highest changes of pore water pressure during compaction had a significant linear relationship with the pre-compression stress (R=0.88, P<0.001). The correlation was ascribed to that the changes in pore water pressure describe the dynamics of the interactive effects of soil pore characters and soil water movement during compaction. The results suggested the evaluation of soil vulnerability to compaction have to consider the initial soil condition and an easy method to measure the changes in pore water pressure can be applied to compare soil strength and soil vulnerability to compaction.     

农田土壤机械压实研究进展与展望

土壤机械压实是威胁全球农业可持续发展的重要因素之一。从农田土壤压实的检测、危害、缓解和预防四个方面系统介绍当前国内外土壤压实的最新研究进展与不足。指出检测方法的创新和突破是实现田间尺度下压实土壤空间分布检测的关键;压实土壤危害的研究多集中在耕层土壤,但忽视了深层土壤压实危害及其在应对气候变化中可发挥的生态服务功能;提倡采用轮作轮耕等合理田间管理措施缓解压实土壤;深层土壤压实具有存在时间久和恢复难度大的特征,因此重点应以预防为主,但当前对土壤压实预防重视不足且预防技术体系尚不成熟。鉴于我国农业机械化正处在快速发展期,采取有效预防措施是避免重蹈发达国家土壤压实退化的有效手段。     

Compaction of an Eutric Cambisol under heavy wheel traffic in Switzerland — field data and modelling

Heavy agricultural machinery can cause structural degradation in agricultural subsoils. Severe structural degradation impedes plant growth. Therefore, compaction must be limited to layers that can be structurally reclaimed and remoulded with reasonable effort by tillage. The purpose of this study was to investigate the impact of a single pass with a sugar beet harvester on the soil properties of an unploughed Eutric Cambisol. Field measurements and laboratory testing were carried out in Frauenfeld, Switzerland. In addition 2D calculations of strain, stress and subsequent compaction were conducted using a three-phase (soil skeleton, pore water, and air) model for unsaturated soil incorporating a recently developed constitutive law. Model data were compared to the field measurements. Due to the pass of the machinery, the soil was compacted down to a depth of at least 0.15 m and at most 0.25 m. This compaction was indicated by an increase in soil bulk density and pre-consolidation pressure as well as by a decrease in total porosity and macroporosity. The surface displacement measured in the field was consistent with the calculated model data. The calculated and measured stresses at depths of 0.35 and 0.55 m stand in good accordance with each other, whereas at a depth of 0.15 m the pressure measured in the field exceeded the calculated pressure. In this study, we show the degree of compaction due to heavy wheel traffic and the suitability of a model approach to describe compaction processes.     

Predicting soil workability and fragmentation in tillage: a review

Soil workability and friability are required parameters to consider when creating suitable seedbeds for crop establishment and growth. Knowledge of soil workability is important for scheduling tillage operations and for reducing the risk of tillage‐induced structural degradation of soils. A reliable evaluation of soil workability implies a distinctive definition of the critical water content (wet and dry limits) for tillage. In this review, we provide a comprehensive assessment of the methods for determining soil workability, and the effects of soil properties and tillage systems on soil workability and fragmentation. The strengths and limitations of the different methods for evaluating the water content for soil workability, such as the plastic limit, soil water retention curve (SWRC), standard Proctor compaction test, field assessment, moisture‐pressure‐volume diagram, air permeability and drop‐shatter tests are discussed. Our review reveals that there is limited information on the dry limit and the range of water content for soil workability for different textured soils. We identify the need for further research to evaluate soil workability on undisturbed soils using a combination of SWRC and the drop‐shatter tests or tensile strength; (i) to quantify the effects of soil texture, organic matter and compaction on soil workability; and (ii) to compare soil water content for workability in the field with theoretical soil workability, thereby improving the prediction of soil workability as part of a decision support system for tillage operations.     

金沙江干热峡谷中退化的土壤生态系统生物学特征初探

Distribution characteristics of soil animals,microorganisms and enzymatic activity were studied in the dry red soil and Vertisol ecosystems with different degradation degrees in the Yuanmou dry hot valley of the Jinsha River,China.Results showed that Hymenoptera,Araneae and Collembola were the dominant groups of soil animals in the polts studied.The numbers of groups and individuals and density of soil animals in the dry red soil series were higher than those in the Vertisol series,and the numbers of individuals and density of soil animals decreased with the degree of soil degradation.Bacteria dominated microbiococnosis not only in the dry red soils but also in the Vertisols.Microbial numbers of the dry red soil series were higher than those of Vertisol series,and decreased with the degree of soil degradation.The activities of catalase,invertase,urease and alkaline phosphatase declined with the degradation degree and showed a significant decline with depth in the profiles of both the dry red soils and the Vertisols,but activities of polyphenol oxidase and acid and neutral phosphatase showed the same tendencies only in the Vertisols.It was concluded that the characteristics of soil animals,microorganisms and enzymatic activity could be used as the bio-indicators to show the degradation degree of the dry red soils and Vertisols.Correlation among these soil bio-indicators was highly significant.     

Field compaction at different soil-water status: effects on pore size distribution and soil water characteristics of a Rhodic Ferralsol in Western Cuba

The level of compaction induced on cultivated fields through trafficking is strongly influenced by the prevailing soil-water status and, depending on the attendant soil degradation, vital soil hydraulic processes could be affected. Therefore, understanding the relationship between field soil-water status and the corresponding level of induced compaction for a given load is considered an imperative step toward a better control of the occurrence of traffic-induced field soil compaction. Pore size distribution, a fundamental and highly degradable soil property, was measured in a Rhodic Ferralsol, the most productive and extensively distributed soil in Western Cuba, to study the effects of three levels of soil compaction on soil water characteristic parameters. Soil bulk density and cone penetration index were used to measure compaction levels established by seven passes of a 10 Mg tractor at three soil-water statuses corresponding to the plastic (Fs), friable (Fc) and relatively dry soil (Ds) consistency states. Pore size distribution calculated from soil water characteristic curves was classified into three pore size categories on the basis of their hydraulic functioning: >50 μm (f_>50 μm), 50–0.5 μm (f_{50–0.5 μm}) and <0.5 μm (f_<0.5 μm). The greatest compaction levels were attained in the Fs and Fc soil water treatments, and a significant contribution to compaction was attributed to the existing soil water states under which the soil compaction was accomplished. Average cone index (CI) values in the range of 2.93–3.70 MPa reflected the accumulation of f_<0.5 μm pores, and incurred severe reductions in the volume of f_>50 μm pores in the Fs and Fc treatments, while an average CI value of 1.69 MPa indicated increments in the volume of f_{50–0.5 μm} in the Ds treatment. Despite the differential effects of soil compaction on the distribution of the different pore size categories, soil total porosity (f_Total) was not effective in reflecting treatment effects. Soil water desorption at the soil water potentials evaluated (0.0 to −15,000 cm H₂O) was adversely affected in the f_<0.5 μm dominated treatments; strong soil water retention was observed with the predominance of f_<0.5 μm, as was confirmed by the high water content at plant wilting point. Based on these findings, the use of field capacity water content as the upper limit of plant available soil water was therefore considered inappropriate for compacted soils.