This collection, Soil Geography and Classification of Asia, aims to provide a general understanding of the soil cover of several Asian countries that have received relatively little attention in past research. It also seeks to present to the wider scientific community the latest materials concerning theories of soil formation and to demonstrate their practical significance. A number of contemporary issues related to the classification of Asian soils were discussed at the UNESCO/FAO International Seminar held in Tashkent in 1962. Selected materials from that seminar have been included in this volume. The first section of the collection contains articles devoted to the soils of arid regions. It opens with a paper by E. V. Lobova on the classification of desert soils of the Asian continent. Desert soils occupy an immense area extending from the Caspian Sea westward to the mouth of the Yellow River. The marked differences in the properties of these soils are related to the bioclimatic characteristics of Western and Central Asia. Research has shown that carbonate and salt profiles, humus types, and clay-formation characteristics differ significantly between Western and Central Asia. Taking into account the general genetic characteristics of these soils and their variations associated with parent materials, degrees of salinization, and historical development, researchers consider it possible to establish a classification scheme for desert soils, distinguishing soil classes, subclasses, and types. Such classification is closely related to vegetation characteristics and agricultural utilization. A separate article by B. V. Gorbunov is devoted to the classification of irrigated soils. Since mountain systems occupy vast areas of the Asian continent and selective utilization of mountain soils has already begun, the problem of classifying mountain soils has become particularly urgent. A. M. Mametov’s article on soil classification, vertical zonation, and provincial differentiation in the Kyrgyz Soviet Socialist Republic describes the soil cover of that republic and demonstrates methods that may successfully be applied to the classification of soils in other mountainous countries of Asia. The soils of other Asian countries are described in reports dealing with Iraq (M. L. Devine), Afghanistan (Subramanian, Naserov, and Zarif-Salim), and Syria (Van Lier). M. L. Devine’s article describes the characteristics of the soils of Iran. The soils referred to in the article as “brown soils,” according to their descriptions, resemble typical or even dark sierozems. The chestnut soils described by Devine may perhaps be equivalent to the “brown soils” discussed by Alambayev elsewhere in this volume. Iranian chestnut soils are characterized by a relatively high humus content of 3–4 percent; their upper horizons have a neutral reaction, and carbonates appear at depths of 30–40 cm. The soils of the most humid regions of Iran, including Mazandaran and Gorgan Provinces, are classified as brown forest soils, red-yellow podzolized soils, and red and brown Mediterranean-type soils. The characteristics provided make it possible to compare these soils with similar soils of Transcaucasia. In the concluding section of his work, M. L. Devine proposes an agricultural-production grouping of soils and presents data on the area of soils suitable for different crops. The article by Subramanian, Salim, and Naserov is valuable as the first general survey of Afghan soils prepared by soil scientists of that country. Until now, information on Afghan soils has largely been based on indirect evidence from studies by agronomists and geobotanists, including N. I. Vavilov, N. G. Chernyakovskaya, A. V. Prozorovsky, and L. E. Rogin. The paper provides new data on sierozems and other soils. Afghan sierozems differ from the typical sierozems of the Soviet Union in the presence of a distinctly compact, slightly reddish B horizon (argillic horizon) and somewhat different patterns of carbonate distribution. Van Lier’s article provides an overview of the soils of Syria and their utilization. In the mountainous regions of Syria, soils comparable to the brown leached soils and brown forest soils of the Soviet classification occur. The Syrian steppe zone is regarded as supporting semi-savanna vegetation. According to the author, the soils of the desert zone are associated with stony, gypsiferous, and alluvial parent materials. The author points to the high carbonate content and salinity of many Syrian soils but considers salinity control in Syria to be a relatively manageable problem. The article by L. E. Rogin and N. I. Bazilevich describes the sierozem and desert soils of Syria and the Soviet Union. Closely linked to soil characteristics, the study examines the biological cycling of ash elements and nitrogen within soil-plant systems. The article contains original data and conclusions concerning the typology of biological cycling in desert and semi-desert environments as well as the proportions of chemical elements contained in soils and vegetation biomass. Together with Van Lier’s paper, this work facilitates comparison between soil-forming processes in subtropical arid regions such as Syria and subboreal arid regions of the Soviet Union. It is evident that subtropical desert soils are characterized by more pronounced migration of iron within the profile, giving them a redder coloration and higher carbonate contents in the lower horizons. In the subtropical sierozems of Syria, a leached horizon is clearly visible, and soil profiles are generally not very thick. Pronounced leaching is accompanied by weak clay translocation, which appears to be an important diagnostic characteristic of these subtropical soils. The articles by M. A. Abdullayev (Uzbek Soviet Socialist Republic) and M. Alambayev (Turkmen Soviet Socialist Republic) are devoted to the study of brown soils. Particularly interesting is their description of the two extreme variants of these soils: the driest Turkmen variant and the relatively humid Uzbek variant. The brown soils of Turkmenistan develop under arid steppe vegetation. Their investigation confirmed and expanded existing concepts regarding the accumulation of clay in the middle part of the profile. In brown dry-steppe soils, weak weathering processes, hydromica clay minerals, and accumulations of kaolinite were identified. The occurrence of kaolinite may be regarded as evidence of the more humid climatic conditions that prevailed in Turkmenistan during the Tertiary period. The authors argue for the necessity of distinguishing two types of brown soils: the “dry-steppe type” and the “forest type.” Brown dry-steppe soils are considered similar to the “chestnut soils” of Iran, whereas brown forest soils resemble the “brown Mediterranean-type soils” described for Iran. Accordingly, it is considered necessary to distinguish between dry-steppe brown soils and brown soils that develop in humid regions. The brown soils of the Zeravshan mountain system exhibit a greater degree of leaching, as indicated by the deeper occurrence of carbonate effervescence. Observations made during field excursions associated with the Tashkent seminar stimulated extensive discussion between Soviet and foreign soil scientists. Subsequently, R. Ménier published an article summarizing these discussions and comparing brown soils from various regions. R. Ménier and other foreign participants in the seminar considered the brown soils of Crimea equivalent to “Mediterranean-type chestnut soils,” whereas those of Uzbekistan were regarded as similar to brown forest soils. It should be noted that these soils had previously been termed “meadow-brown soils” by A. N. Rozanov. Ménier emphasized that Mediterranean-type chestnut soils develop under climates with warm winters and therefore exhibit stronger leaching, greater release and migration of iron, and other distinctive features. Soviet brown soils, by contrast, develop under cold-winter conditions and are characterized by weaker leaching, lower iron mobility, and greater humus accumulation. M. G. Kornbergskaya’s article examines the desertification process affecting soils developed on alluvial deposits under irrigation. Comparisons with archaeological evidence made it possible to estimate the age of desert soils. For example, the youngest “gray desert soils” appear roughly one hundred years after irrigation ceases, while older desert soils exceed 500–600 years in age. The article also provides specific data concerning the influence of vegetation on soil formation. M. A. Muravyova and Z. B. Shelitrennikova present detailed studies of the characteristics of humus formation in light, typical, and dark sierozems, brown soils, and meadow-marsh soils of Uzbekistan. The authors closely investigated the rate and characteristics of plant-residue decomposition and determined the influence of humification processes on the composition of different humus fractions. Their work revealed a number of specific characteristics of the humus status of the principal soils of Uzbekistan. M. A. Rish’s article, “Trace Elements in Desert Soils and Sierozems of Uzbekistan,” contains original and highly valuable data and conclusions. Although desert soils and sierozems have been extensively studied within the Soviet Union, their trace-element composition had never previously been investigated in such detail. Studies of the relationship between trace elements in soils and plants demonstrate their value in improving soil diagnosis. Morphologically indistinct horizons, such as the B horizon in sierozems, can be identified more reliably through trace-element accumulation. In other situations, concentrations of trace elements may indicate ongoing soil-forming processes. The materials presented portray a broad picture of biogeochemical processes within soil-plant systems and provide a basis for evaluating soil fertility and developing recommendations for agricultural and livestock management. The second section of the collection contains articles devoted to tropical countries. It provides readers with a general understanding of the soil cover of India, Brazil, the Federation of Malaya, and other tropical regions. Descriptions of equatorial and tropical forest soils by Soviet specialists are presented in papers by M. Camargo, K. R. Panabok, and V. P. Panton. N. R. Panabok presents a clear classification of the “major soil categories” of Ceylon. Particularly interesting are the diagnostic criteria used to distinguish the principal soil categories, which correspond roughly to soil types in Soviet terminology. Six categories are described in detail. For Soviet readers, it is valuable to compare soil-profile characteristics with the climatic conditions of Ceylon. Lateritic soils develop under humid tropical forests receiving up to 5,000 mm of annual rainfall distributed relatively evenly throughout the year. These lateritic soils, known as “red and yellow latosols,” are intensely weathered: they contain no unweathered minerals and possess uniform profiles lacking a distinct B horizon. The soils of the “transitional and dry zones,” where annual precipitation ranges from 200 to 2,500 mm, are termed “brown non-calcareous soils.” These soils possess a developed B horizon with clay coatings on aggregate surfaces. Their cation-exchange capacity is relatively low, ranging from 25 to 40 milliequivalents per 100 grams of clay. They contain relatively small quantities of iron- and magnesium-bearing minerals. In the “dry” zone, receiving less than 1,625 mm of annual precipitation, “red-brown soils” with a textural B horizon develop. The horizon is more strongly expressed and clay coatings are clearly visible. Their cation-exchange capacity is higher, reaching 45–50 milliequivalents per 100 grams of clay. In addition to kaolinite, these soils contain illite and large quantities of montmorillonite. Similar soils in Indonesia are known as “red Mediterranean-type soils.” Camargo’s classification of Brazilian soils is broadly based on the same principles, although these are not always applied consistently, since highly fertile soils such as terra roxa and infertile soils are included within the same grouping. The criteria used to distinguish “lateritic soils” are difficult to accept without reservation. In V. P. Panton’s article, soil categories are distinguished with consideration for both their genetic significance and fertility levels. Panton emphasizes that growing interest in achieving maximum utilization of national soil resources has created a pressing need for soil mapping. He reviews the history of soil studies in the country and highlights the important role played by geological surveys. The characteristics of the soils described by the author are presented in considerable detail. Particularly interesting are the soils occurring under teak forests. Panton notes a remarkable phenomenon: soils classified diagnostically as poor lateritic soils can nonetheless produce satisfactory yields. This results from several factors: if unweathered bedrock lies close to the surface, roots can obtain nutrients from it; the good structural condition of lateritic soils creates favorable moisture and aeration regimes; and erosion may remove the infertile surface horizon, exposing weakly weathered parent material near the surface. An unusual situation is that soils formed on alluvial deposits are often among the least fertile because, according to Panton, these deposits and soils have undergone a “double cycle of weathering.” The soils of arid tropical savannas are discussed in the articles of S. P. Raychaudhuri and R. Ménier. A general description is also provided by R. Askaev. The black cotton soils of the Indian savannas are proposed to be divided into three groups according to profile thickness. In addition, “red soils” of the savannas of southern India are distinguished. Raychaudhuri compares the Indian soil-classification system with the legend of the Soil Map of Asia. R. Ménier’s article summarizes many years of research on the semi-arid soils of West Africa. These studies make it possible to compare soils of tropical semi-arid regions across different continents and hold promise for the eventual establishment of a global system for the diagnosis and classification of arid and semi-arid soils. At present, however, major differences in terminology and concepts remain. For example, French soil scientists consider only Sahara-type deserts and comparable regions to be true deserts, whereas the deserts and desert soils of the Soviet Union are regarded as belonging to semi-arid regions and semi-arid soil categories. According to Ménier, tropical semi-arid brown soils differ from temperate semi-arid soils in that iron migrates extensively within the profile, salinization and alkalization are not strongly developed, and a clay-rich B horizon forms. Ménier discusses the processes of calcification, ferruginization, clay formation, and steppification. His discussion of steppification is somewhat general and does not include detailed consideration of humus-formation types. In addition to the articles dealing with major soil categories, or zonal soils in Soviet terminology, the collection also includes papers on the soils associated with rice cultivation, the principal food crop of Southeast Asia. These include studies of paddy soils (R. Dudal), degraded soils (B. G. Rozanov), meadow soils (I. I. Karmanov), and the meadow soils of Guinea (N. V. Kimberg). The theoretical and practical significance of these detailed investigations is beyond doubt. Modern soil science employs a wide variety of methods that permit more comprehensive determination of soil properties and nature. Major advances have undoubtedly been achieved in the study of the physical, chemical, and mineralogical characteristics of soils. The nature of soil humus is perhaps the single most important factor in the formation of soil types. For this reason, the collection includes a paper by N. T. Muravyova dealing with humus types in the arid latitudes of the subboreal zone. The articles collected in this volume introduce readers to new information concerning the arid and tropical regions of Asia, clarify the genesis of a number of soils, and thereby contribute to determining the place of Asian soils within the broader context of the soils of other continents. Overall, this collection represents a major scientific contribution to the study of Asian soils. It also stands as a symbol of the creative cooperation of scientists from many countries working together for the common advancement of agriculture.