Cracked soil and its varieties are widely distributed in the desert areas of Central Asia, and in many cases constitute a part of land resources suitable for the expansion of irrigation systems. For example, in the ancient Delta region of the Amu Darya River, cracked soil and similar soils account for more than half of the land resources suitable for irrigation. The same is true for the southern and southwestern regions of Turkmenistan. Here, in the upper part of the plot adjacent to the koppet mountain, there are mainly high fertility light gray calcareous soil without improvement. In the lower lying areas closer to the sea and Karakum Desert, the soil cover is dominated by fissured soil and fissured soil, which is mixed with a large area of saline soil and part of sand. In these areas, cracked soil and similar soils account for at least 70% of the soil cover. Fissured soil is also found in the sandy land of Karakum and Sangsang. The cracked soil here has a very high clay content, is often salinized, and is extremely compact (hard). It is not particularly difficult to reclaim and irrigate lightly meadow soil. However, in fact, there is no improvement and reclamation method for cracked soil. Obviously, it is necessary to solve the complex problem of improvement to develop irrigated agriculture in the cracked soil distribution area. Irrigation agriculture has little experience in the management and utilization of cracked soil and similar soils, although in terms of topographic conditions, the vast majority of areas occupied by cracked soil are extremely conducive to the development of irrigation. The reclamation of fissured soil faces many difficulties: they have low humus content, weak biological activity, a layer of hard crust 5-7 cm thick on the surface, no structure, most of which have heavy clay mechanical composition, often salinized, high alkalinity value, and often contain a certain amount of free soda and magnesium carbonate, and there is exchangeable sodium in the adsorption complex; The water permeability of fissured soil is very poor. Atmospheric precipitation and irrigation water are retained on the surface and difficult to penetrate into the lower layer. Therefore, the biological, chemical and hydro physical properties of fissured soil are extremely unfavorable for crop cultivation. Irrigated agriculture provides collective farms and state farms with fresh water as an important means to eliminate the main obstacle to the improvement and reclamation of cracked soil - the problem of water shortage in these areas. At the same time, powerful agricultural technology and other means can also provide help, so that cracked soil and similar soil can be deep ploughed, scarified, chemical, physical machinery and biological improvement. However, it must be clearly pointed out that the scientific community has not yet developed a proven system of improvement and agricultural technology measures for the fundamental improvement of cracked soil and similar soils. The necessity of studying the causes and types of fissured soil and the causes of its low fertility has been underestimated for a long time. So far, we have not recognized the theory of fissured soil genesis. There are few studies on the classification and system of these soils, their seasonal dynamics are unknown, and biological data are scarce. It is worth noting that in the relatively and absolutely older high plains of Turkmenistan, cracked soil is missing or extremely rare. On these surfaces, the soil cover is mainly gray brown soil or gray calcareous soil. Fissured soil is also not found on young flood delta sediments affected by floods and groundwater. The soil cover here is usually meadow soil and meadow saline soil riparian forest soil. It is reasonable to speculate that the cracking stage of soil cover in the extreme arid region of Southwest Central Asia is related to the history of the whole landscape, and only occurs when the process of hydro meadow meadow and salinization is replaced by the process of desert grassland under specific conditions. However, we still have no clear picture of the emergence, development and replacement stages of the cracking soil formation process. The existing geographical data show that the formation process of crazing is a typical feature of most plain areas in Turkmenistan. Not only that, they are also representative of the driest regions in Central Asia, which is a unique geographical phenomenon (zone, province). In southwestern Central Asia, almost all types of modern sediments may be covered with cracked crusts (dense and impermeable). The formation of fissured soil and fissured soil on clay, loam and sandy soil can be observed, which are the products of fluvial, diluvial and blown sediments or paleo alluvial proluvial sediments. Ancient Adobe architectural relics and collapsed courtyard walls are often covered with cracked crusts. Signs of the formation of crazing crusts can be seen in the light colored desert calcareous soil in the koppet mountains and the saline soil in the ancient delta of the Amu Darya and atlek rivers. However, up to now, we are still unable to fully explain the reason why the crazing phenomenon is so widely distributed. Similarly, it failed to fully reveal a series of reasons for the extremely low fertility of fissured soil. Obviously, the improvement and agricultural technology measure system aimed at fundamentally improving the cracked soil should include: washing the salt content of the cracked soil, eliminating its high alkalinity, destroying the crusts, increasing the application of organic matter, realizing the biological activation of the soil by increasing the number and species diversity of microorganisms and macro fauna and flora in the soil, creating the aggregate structure with agronomic value, and fundamentally improving its hydro physical properties. Comparative geographical observations have led us to speculate that the natural evolution direction of fissured soil is to colonize angiosperms and form grayish brown soil, and in some cases form grayish calcareous soil. The evolution process of fissured soil is often triggered by the presence of sandy sediments on its surface, accompanied by the colonization of higher plants in the soil. These plants accumulate organic matter and act on the soil through the root system, resulting in the cracked soil gradually losing its unique characteristics and improving its fertility. There are a few cases of successful reclamation of cracked soil for agriculture. Irrigation, sand mixing, wall soil application, grass planting and systematic high-quality tillage have gradually improved the cracked soil. Such examples can be found in the southwest Turkmen, Murgab and jejan River regions, and Karakal park. All these show that the current barren land state of the cracked soil is relative and can be overcome. The existing scientific data (although limited), laboratory tests and the production experience of collective farms have proved that the improvement and reclamation of cracked soil can be completely solved. The task of the authors' team of this book is to critically review and summarize the existing scientific literature, experimental and production materials, and improvement methods on the origin and characteristics of cracked soil. The main material of this collective work is the scientific achievements of scientific researchers from several scientific research institutions in the Aral Caspian Sea comprehensive investigation team under the productivity research committee of the Soviet Academy of Sciences, who have carried out a three-year field route survey and fixed-point research on cracked soil in the southern and southwestern regions of Turkmenistan and parts of the lower reaches of the Amu Darya River. The research on fissured soil was carried out by the staff of the Institute of soil research, the Institute of Botany, the Institute of zoology, the Institute of hydrochemistry, the laboratory of Limnology, the productivity research committee of the Soviet Academy of Sciences and the Leningrad National University. The scientific guidance for these studies was VAA kovda. The authors are clearly aware that the three-year investigation and fixed-point research are not enough to thoroughly solve the complex problem of the origin and reclamation of fissured soil. At the same time, they also realized that in the past 15 years, there has not been any work in the literature that comprehensively discusses the origin, characteristics and improvement methods of fissured soil. The designers who plan irrigation system when reclaiming land containing cracked soil are in a very difficult position. However, the construction of such new irrigation systems has been implemented, and it has become an urgent problem to reclaim large areas of cracked soil and similar soil for agriculture in these areas. Therefore, although it is acknowledged that the existing materials are not sufficient, the author of this book still believes that it is necessary to sort them into a certain system, and expounds the basic theoretical views on the origin and characteristics of the cracked soil, as well as the basic principles of its improvement and reclamation. The research results are published in the form of collective monograph, which is divided into four parts: the first part discusses the distribution and formation of fissured soil; The second part investigates the role of vegetation in the evolution of fissured soil; The third part describes its most important characteristics; Finally, the fourth part analyzes the reasons for the natural unfertility of fissured soil and the research results on its improvement and agricultural reclamation.