沿海地区海盐沉降对酸性土壤的影响

The characteristics of sea.salt deposition and its impact on acid soils in maritime regions are reviewed. It is pointed out that studies involving the impact of sea.salt deposition on acid soils have been concentrated on short-term effects on soil and water acidification. A deep consideration of long-term effects on soil acidification in maritime regions is still needed.     

Impacts of land use and salinization on soil inorganic and organic carbon in the middle-lower Yellow River Delta

Soil inorganic carbon (SIC) is an important reservoir of carbon (C) in arid, semi-arid, and semi-humid regions. However, knowledge is incomplete on the dynamics of SIC and its relationship with soil organic C (SOC) under different land use types in the semi-humid region, particularly in coastal zones impacted by soil salinization. We collected 170 soil samples from 34 profiles across various land use types (maize-wheat, cotton, paddy, and reed) in the middle-lower Yellow River Delta (YRD), China. We measured soil pH, electrical conductivity (EC), water-soluble salts, and SOC and SIC contents. Our results showed significant differences in both SOC and SIC among land use types. The dry cropland (maize-wheat and cotton) soils had significantly higher SOC and SIC densities (4.71 and 15.46 kg C m^-2, respectively) than the paddy soils (3.28 and 14.09 kg C m^-2, respectively) in the 0–100 cm layer. Compared with paddy soils, reed soils contained significantly higher SOC (4.68 kg C m^-2) and similar SIC (15.02 kg C m^-2) densities. There was a significant positive correlation between SOC and SIC densities over a 0–100 cm soil depth in dry cropland soils, but a negative relationship in the paddy soils. On average, SOC and SIC densities under maize-wheat cropping were 15% and 4% lower, respectively, in the salt-affected soils in the middle-lower YRD than the upper YRD. This study indicated that land use types had great influences on both SOC and SIC and their relationship, and salinization had adverse effect on soil C storage in the YRD.     

Forms of Rare Earth Elements in Soils: Ⅰ. Distribution

The distribution of rare earth element (REE) forms in soils is given in the present paper on the basis of sequential fractionation and determination of 34 representative surface soils collected from all parts of China.Results obtained show that the extraction rate of water soluble and exchangeable REE had the odd-even phenomenon and that of organically bound REE from La to Lu tended to reduce gradually with the increase of atomic number.The stability of Sc and the activity and enrichment of Tm in soils are proposed.Furthermore,the paper makes a preliminary discussion on the differences in the concentration distribution of various forms of individual REE in some soils.     

Spatial Characteristics of Soil Organic Carbon Storage in China＇s Croplands

The soil organic carbon （SOC） pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and based on 1546 typical cropland soil profiles, the paddy field and dryland SOC storage among six regions of China were systematically quantified to characterize the spatial pattern of cropland SOC storage in China and to examine the relationship between mean annual temperature, precipitation, soil texture features and SOC content. In all regions, paddy soils had higher SOC storage than dryland soils, and cropland SOC content was the highest in Southwest China. Climate controlled the spatial distribution of SOC in both paddy and dryland soils, with SOC storage increasing with increasing precipitation and decreasing with increasing temperature.     

中国农田土壤有机碳贮存的空间特征

The soil organic carbon (SOC) pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and based on 1546 typical cropland soil profiles, the paddy field and dryland SOC storage among quantified to characterize the spatial pattern of cropland SOC storage in China regions of China were systematically to examine the relationship between mean annual temperature, precipitation, soil texture features arid SOC content. In all regions, paddy soils had higher SOC storage than dryland soils, and cropland SOC content was the highest in Southwest China. Climate controlled the spatial distribution of SOC in both paddy and dryland soils, with SOC storage increasing with increasing precipitation and decreasing with increasing temperature.     

Forms of Rare Earth Elements in Soils: Ⅱ. Differentiation of Rare Earth Elements

The present paper deals mainly with the relationships between the distribution of rare earth elements (REE) in different forms in soils and the atomic number and with the odd-even phenomenon in the distribution of ionic lanthanides in soils.The enrichment tendency of light REE relative to heavy REE in soils was pointed out on the experimental results about the proportions of Ce-group and Y-group elements in different REE forms in soils.Meanwhile,the differentiation of Tm in different soil REE forms was compared and the reasons why Tm is enriched in soils were preliminarily discussed.     

Necessity for quantified measurement of soil sodicity and selection of suitable gypsum amendment for proper reclamation of sodic soils

<正>Dear Editor,Soil sodicity is the primary limiting factor in sustainable crop production in arid and semiarid regions, where the water scarcity, low rainfall, and poor-quality (salty) groundwater are common occurrence (Datta et al., 2019; Hosain,2019; Minhas et al., 2019; Kumar and Sharma, 2020).Globally, five categories of salt-affected soils have been identified, based on the nature and composition of salts(Szabolcs and Várallyay, 1971; Kovda, 1973; Szabolcs,1989). These soils are sali...     

中国南亚热带农业土壤中的多环芳烃

The contributions of persistent organic pollutants （POPs） from the subtropical regions of China to pollution of the global environment have been paid great attention; however, little is known about the state of POPs in agricultural ecosystems within these regions of China. This study primarily revealed the state of the contamination and distribution of polycyclic aromatic hydrocarbons （PAH） in agricultural soils in the subtropical regions. 115 surface soils （0-20 cm） were sampled in the breadbaskets of these regions. The concentrations and types of PAH were determined using gas chromatography linked to mass spectrometry （GC-MS）. The total PAH concentrations ranged from 22.1 to 1 256.9 ng g^-1 with a mean of 318.2 ± 148.2 ng g^-1. In general terms, the current PAH concentrations were lower than most PAH levels reported in a number of investigations from different countries and regions. PAH isomer ratios indicated that pyrolytic origins, such as fossil fuel combustion related to vehicle tail gas and industrial emissions, were the dominant sources of PAH in the southern subtropical areas of China. Although PAH concentrations decreased with decreasing pollution, population, and traffic density, to a great extent PAH compositions were similar throughout subtropical soils, with naphthalene, phenanthrene, fluoranthene, and benzo（b）fluoranthene being dominant.     

Micronutrient Contents of Citrus Orchard Soils in Southern China

Investigations were carried out on the micronutrient contents,of major citrus orchard soils (involving seven soil great groups in 8 provinces and an autonomous region of southern China),and an evaluation on the abundance and deficiency of available micronutrients in these soils was made in this paper.In southern China,citrus orchard soils derived from sandstone,sandy shale,Quaternary red clay,diluvial deposit,granite gneiss and neritic deposit were deficient in available Mo and B and low in Zn.Those developed on purple sandy shale,limestone and slope deposit were all in short supply of available Zn,B and Mo.Coastal solonchak was fairly abundant in B,but its available Fe,Zn and Mo contents were rather low.     

Effect of Potassium Nutrition of Different Varieties of Rice on the Redox Status in Microzone Rhizosphere Soils

Being divided into three groups-strong,moderate and weak-according to the different kinetic parameters (Fmax,km,Cmin) of potassium uptake by crops,21 cultivars of rice have been studied to find out the relationships between their potassium nutrition and the oxidation-reduction status in the rhizosphere soils. Results show that,with no application of K fertilizer,there were higher contents of active reducing substances and ferrous iron in rhizosphere soils planted with cultivars,such as Zhongguo 91,week in absorbing potassium than in soils cropped with cultivars,Shanyou 64,stronger in absorbing potassium.As a result of K application,however,these toxic substances were decreased appreciably in the soil,particularly in the root zone where weakly K-absorbing sultivars were growing,and the parameter of soil redox (pH pE) was increased,the most striking example of this being found in the rhizosphere soil where the more strongly K-absorbing sultivars were growing.On and close to the root surface in soils where rice plants were supplied with potassium fertilizer,rather more iron oxide had been accumulated compared with rice receiving no potash,and even greater amounts of red iron oxide precipitated on the rice root in neutral paddy soils.As shown by the concentration distribution of active reducing substances and ferrous iron in a microzone of the profile,the redox range of rice roots supplied with potassium may extend as far as several centimeters from the root surface.It can thus be seen that potassium nutrition exerts its effect first on the morphological properties of rice roots and their exudation of oxygen,then on the content of soluble oxygen and the count and species of oxygen-consuming microbes in the rhizosphere soil,and finally on the redox status of the soil.     

Salt-affected soils of the Barguzin Depression

Factual materials on salt-affected soils in the Barguzin Depression (Buryat Republic) are generalized. A geomorphic map of the depression has been developed. The distribution of salt-affected soils and the specificity of salinization in different geomorphic regions are characterized. These soils tend to be developed within the low lacustrine–alluvial plain of the depression, on the floodplain of the Barguzin River and its tributaries. Smaller areas of salt-affected soils are found on the river terraces. They are virtually absent on ancient sandy ridged terraces (kuituns). The genesis and chemistry of soil salinization are mainly related to the discharge of slightly saline deep water along tectonic faults and fissures. An additional source of soil salinity is represented by surface water flows. The presence of permafrost preventing the leaching of salts and the cryoarid climate favoring the migration of salts toward the soil surface during the dry spring and early summer periods and during the soil freezing in the winter contribute to the soil salinization. Slightly saline hydromorphic solonchakous soils predominate among salt-affected soils of the depression; the portion of semihydromorphic saline soils is smaller. Automorphic saline soils rarely occur in the depression. Strongly saline soils— solonchaks—are widespread within lacustrine depressions around salt lakes. Soils of the soda and sulfate salinization predominate. The content of chlorides is small; their increased amounts, as well as the presence of sulfates, are indicative of the discharge of dee ground water onto the surface. The soda type of salinization is also related to the discharge of deep stratal water with further transformation of salt solutions during freeze–thaw cycles. Under anaerobic conditions, the formation of soda is favored the processes of sulfate reduction.     

Climate and soil salinity in the deserts of Central Asia

A comparative analysis of climatic and soil salinity characteristics of the deserts of Central Asia, including deserts of the Turan Depression, the Gobi Desert, and deserts of the Dzungar and Tarim depressions was performed. The climatic characteristics—the degree of aridity, the degree of continentality, and the amount and regime of precipitation—are different in these deserts. No direct relationships between the areas occupied by the automorphic salt-affected soils and the aridity of the climate are observed in the studied regions. In the automorphic landscapes of Asian deserts, the degree and chemistry of the soil salinization and the distribution of salt-affected soils are controlled by the history of the particular territories rather than by their modern climatic conditions. The presence and properties of the salt-bearing rocks and the eolian migration of salts play the most significant role. The deficit of moisture in the modern climate favors the preservation of salt accumulations in places of their origin. The specific features of the climate, including the regime of precipitation, affect the redistribution of salts in the profiles of automorphic salt-affected soils. An increase in the degree of climatic continentality is accompanied by the decrease in the intensity of weathering and initial accumulation of salts. A different situation is observed in the soils of hydromorphic desert landscapes, in which the degree of salinity of the surface horizons and the area occupied by salt-affected soils are directly influenced by the modern climatic conditions.     

Zonal,provincial, lithological,and geomorphic features of soil salinization in the Southern federal okrug of Russia

The relationships between soil salinization and the zonal and provincial bioclimatic conditions, the lithological composition of the sediments, and the geomorphic features of the territory have been analyzed for the Southern federal okrug of Russia. It is shown that the lithological and geomorphic conditions (relief, salinity of parent materials, degree of drainage, and the depth of saline groundwater) play an important role in the distribution of salt-affected soils against the background of the more general regularities specified by the climate. The participation of salt-affected soils in the soil cover of the Southern federal okrug increases in the eastward direction from the forest-steppe zone to the semidesert zone in agreement with an increase in the aridity and continentality of the climate. The chemical composition of soil salts also changes: the sulfate and soda-sulfate types predominate in the forest-steppe zone; the sulfate type or the sulfate type with the participation of soda, in the steppe zone; the sulfate-chloride type, in the dry steppe zone; and the chloride type, in the semidesert zone. The lithological and geomorphic conditions within the particular zones and provinces affect the distribution pattern of the salt-affected soils and the degree and chemistry of the soil salinization. The areas of salt-affected soils were calculated with the use of a digital version of the Map of Salt-Affected Soils of Russia (1: 2.5 M scale) with due account for the participation of these soils in the soil cover of the particular delineations and the data on the depth of the upper boundary of the salt-bearing horizons, the degree and chemistry of the soil salinization, and the area of solonetzes and solonetzic soils.     

中国盐渍土研究：历程、现状与展望

盐渍土研究是以盐渍土和盐渍生境作为主要研究对象，以盐渍土和盐渍化的发生与演变过程、环境要素和人类活动对盐渍化的影响与作用机制、盐渍土的治理、改良和利用的理论与技术为主体的研究领域。我国盐渍土面积巨大、种类繁多，盐渍化问题突出，对农业生产和生态环境造成不同程度的影响。我国科学家提出的盐渍土“水盐调控”“水盐平衡”，“淡化肥沃层”和“障碍消减”等理论与技术方法，为发展农业生产、提高土地产能、保障粮食安全、拓展耕地资源等发挥了积极作用。近期我国在土壤盐渍化演变过程的监测与多源数据融合、土壤水盐运移过程模拟与尺度转换、盐渍农田养分循环与减损增效、盐渍障碍的生态消减、盐渍障碍微生物修复、盐渍农田灌排优化管理与边际水安全利用等方面取得了积极的进展和成果。建议今后深入开展盐渍土精准控盐的高效和安全用水、土壤盐渍障碍的绿色消减与健康保育、盐渍农田养分库容扩增与增碳减排、土壤盐渍化与区域生态的耦合响应和协同适应等方面的理论与技术研究。应面向农业、资源、生态、环境等领域和行业，致力于拓展理论和新技术的研究，为国家农业升级、粮食安全、耕地保护、生态安全、高质量发展发挥重要作用。本文回顾了我国盐渍土研究工作的...     

Soil salinization in different natural zones of intermontane depressions in Tuva

Soil salinization features in semidesert, dry steppe, and chernozemic steppe zones within intermontane depressions in the central part of the Tuva Republic are discussed. Chernozems, chestnut soils, and brown desert-steppe soils of these zones are usually nonsaline. However, salinization of these zonal soils is possible in the case of the presence of salt-bearing parent materials (usually, the derivatives of Devonian deposits). In different natural zones of the intermontane depressions, salt-affected soils are mainly allocated to endorheic lake basins, where they are formed in places of discharge of mineral groundwater, and to river valleys. The composition and content of salts in the natural waters are dictated by the local hydrogeological conditions. The total content of dissolved solids in lake water varies from 1 to 370 g/L; the water is usually of the sulfate–chloride or chloride–sulfate salinity type; in some cases, soda–sulfate water is present. Soil salinity around the lakes is usually of the chloride–sulfate–sodium type; gypsum is often present in the profiles. Chloride salinization rarely predominates in this part of Tuva, because chlorides are easily leached off from the mainly coarse-textured soils. In some cases, the predominance of magnesium over sodium is observed in the composition of dissolved salts, which may be indicative of the cryogenic transformation of soil salts. Soda-saline soils are present in all the considered natural zones on minor areas. It is hardly possible to make unambiguous statements about the dominance of the particular type of salinity in the given natural zones. Zonal salinity patterns are weakly expressed in salinization of hydromorphic soils. However, a tendency for more frequent occurrence of soda-saline soils in steppe landscapes and chloride–sulfate salinization (often, with participation of gypsum) in the dry steppe and semidesert landscapes is observed.     

Predicting the Classes and Distribution of Salt-Affected Soils in Northwest Libya

Sodicity and salinity can adversely affect soil structure and are common constraints to plant growth in arid regions. Current remote sensing techniques cannot distinguish between the various classes of salt-affected soils. Field and laboratory measurements of salt-affected soils are time-consuming and expensive. Mapping of the salt-affected soils can be used in soil conservation planning to identify regions with different degrees of limitations. There is a need to use existing field and laboratory measurements to create maps of classes of salt-affected soils. The objectives of this study are to classify salt-affected soils, use existing field data to interpolate and validate geospatial predictions of the classes of salt-affected soils using Geographic Information Systems (GIS), and create maps showing the different classes and distribution of salt-affected soils. The classification framework for salt-affected soils is based on electrical conductivity (ECe), soil pH and the sodium adsorption ratio (SAR), and provides four degrees of limitations to salt-affected soils: slight (normal soils), moderate (saline soils), severe (sodic soils), and extreme (saline-sodic soils). Spatial interpolation of the field data from northwestern Libya was verified by cross-validation, and maps of the salt-affected soils in the region were created. The majority of soils in this region of Libya are normal (slight degree of limitation). Twenty percent of the topsoil is saline-sodic (extreme degree of limitation). Land use recommendations and rehabilitation strategies can be developed from such maps of salt-affected soil classes. The methodology followed in this study can be applied to other arid regions around the world, particularly in developing countries where budgetary constraints limit detailed field and laboratory measurements of sodicity and salinity.     

The influence of soil salinization on land use changes in azov district of Rostov oblast

A retrospective monitoring of changes in land use on cultivated salt-affected soils of Azov district in Rostov oblast for a period from 1968 to 2013 was performed within the framework of the creation of a problem- oriented system of retrospective monitoring of the soil cover and land uses. A higher dynamism of land uses on salt-affected soils in comparison with that on nonsaline soils was shown. A decisive role of the anthropogenic factor in the increasing soil salinization in the region was established. The areas of meadow ecosystems with participation of salt-affected soils considerably increased at the end of the 1960s–the beginning of the 1970s. It is argued that their development with a corresponding worsening of the salt status of regional soils was initiated by the wide-scale planting of shelterbelts in the 1940s and 1950s.     

Estimation of the areas of salt-affected soils in the European part of Russia on the basis of a digital map of soil salinization on a scale of 1 : 2.5 M

A digital version of the map of salt-affected soils on a scale of 1 : 2.5 M has been used to calculate the areas of these soils in the four federal okrugs (the Southern, Central, Volga, and Northwestern) of European Russia. The total area of soils with soluble salts in the upper meter reaches 23.3 million ha. More than half of them are solonchakous soils (with soluble salts in the layer deeper than 30 cm), and about 25% are saline from the surface. Soils of sulfate and chloride-sulfate salinization predominate (>50% of the area of salt-affected soils). Alkaline soda-saline soils and soils with the participation of soda comprise about 6%. We consider this value to be underestimated and requiring refinement, because soils of solonetzic complexes with neutral salts in the upper horizons may also contain soda in the solonetzic and subsolonetzic horizons, which was not always taken into consideration upon assessing the chemical composition of the salts. Solonetzes proper and solonetzic soils predominate among the salt-affected soils in the European part of Russia. The area of solonetzes is up to 9.4 million ha. The area of solonetzic soils (including solonetzic soils with salts in the layers of 0–100 and/or 100–200 cm) is 15.5 million ha. The highest percentage (32.2%) of salt-affected soils is in the Southern federal okrug.     

Technogenic Layers in Organic Soils as a Result of the Impact of the Soda Industry

This study focused on characterization of salt-affected organic soils with thin surface mineral layers affected by waste of soda industry in the Inowroc?aw city area, Poland. The obtained results pointed out that the eolian supply of mineral material from waste ponds and locally, its transport by surface runoff can effect formation of layers contained up to 43% of carbonates. In addition, it was shown that these seemingly small transformations in the soil morphology can have a significant impact on functioning of the studied soils in the landscape. In this regard, the most important were deterioration of water properties and reduction of plant growth due to the salinization and sodification. Specific features of the studied soils could be well reflected in the WRB soil name as Eutric Murshic Histosols (Akromineralic, Salic, Sodic, Prototechnic). However, in the Author’s opinion, the introduction of the new qualifier defining the artifact type in the name (i.e. Calcitechnic) would be advisable.     

The effect of the microrelief on salinization of semidesert soils

The microrelief affects the distribution of soluble salts in the upper horizons of salt-affected soils. This has been shown for semidesert soils—meadow solonchak, solonchakous meadow, and meadow soils—within the Sulak Lowland in the Republic of Dagestan. The total content of salts and the concentrations of sodium, magnesium, chlorine, and sulfate ions are higher in the soils of microelevations. However, no significant effect of the microrelief on the distribution of calcium in the soil water extracts has been found. The properties of the solid soil phase (the humus content and the content of adsorbed bases, including calcium, magnesium, and sodium) and the soil pH are not reliably differentiated by the elements of the local microtopography.