China is rich in soil resources, which is rare in the world. The main types of soil occurrence in China can be summarized as red soil, brown soil, cinnamon soil, black soil, chestnut soil, desert soil, fluvo-aquic soil (including Jiang Sha black soil), irrigated silt soil, paddy soil, wet soil (meadow and swamp soil), saline-alkali soil, lithologic soil and alpine soil.
red soil series
The important soil resources in tropical and subtropical areas of southern China are latosol, dry laterite (savanna soil), latosol (latosol), red soil and yellow soil in turn from south to north.
bauxite
It develops in the tropical rain forest or the strongly aluminized acid soil under monsoon forest, and its distribution area in China is small. The analysis data of latosol in Hainan Island show that the weathering degree is very high, the silica-alumina ratio of clay particles (the same below) is lower than 1.5, and clay minerals contain more gibbsite, kaolinite and hematite, with small cation exchange capacity and highly unsaturated base.
Dry laterite
The soil formed under savanna in tropical dry and hot areas is distributed in the southwest of Hainan Island and the Hongshui River basin in southern Yunnan, with low degree of aluminization and calcareous reaction.
Lateritic red soil
It grows under the evergreen broad-leaved forest in the south subtropical zone and has some properties of red soil and latosol.
Red soil and yellow soil
All of them are aluminized acidic soil generated under subtropical evergreen broad-leaved forest. The former is distributed in areas with obvious changes in dry and wet seasons. The sediments are reddish-brown or orange-red, and there are reticular structures and iron-manganese nodules in the lower part of the profile. The ratio of silicon to aluminum is 1.9 ~ 2.2, and the clay minerals are kaolinite, hydromica and gibbsite. The latter is distributed in foggy and humid areas, mainly in Sichuan and Guizhou. It is characterized by yellow or waxy yellow deposits in wet soil layer and middle section, and clay minerals contain more goethite and limonite.
Red soil series is suitable for developing tropical and subtropical cash crops, fruit trees and trees. Crops can be cropped twice a year, even three or four times a year, and the soil production potential is great. At present, there are still a large area of barren hills and hills to be transformed and utilized according to local conditions. Brown soil series is also developed under forests in humid areas of eastern China, including yellow brown soil, brown soil, dark brown soil and floating dust from south to north.
yellow brown soil
Weak aluminized, clayey and acidic soils developed under evergreen broad-leaved forest in subtropical deciduous broad-leaved forest are distributed in the lower reaches of the Yangtze River, between yellow soil, red soil and brown soil, and the soil properties have some characteristics of yellow soil, red soil and brown soil.
umber
Mainly distributed in Liaodong Peninsula and Shandong Peninsula in warm temperate zone, it is a neutral to slightly acidic soil developed under green broad-leaved forest or mixed coniferous and broad-leaved forest in summer. It is characterized by a brown sedimentary clay layer below the humus layer, and the weathering degree of soil minerals is low, with a silicon-aluminum ratio of about 3.0. Clay minerals are mainly composed of hydromica and vermiculite, with a small amount of kaolinite and montmorillonite, and the salt base is close to saturation.
Dark brown calcium soil
Dark brown soil, also known as dark brown soil, is soil developed under temperate coniferous and broadleaved mixed forests or coniferous forests, and distributed in the mountains and hills in the eastern part of Northeast China, between brown soil and floating dust. Different from brown soil, the accumulation of humus is obvious, the leaching deposition process is more intense, the cohesive layer is dark brown, and dark humus spots and silica powder are often seen on the structural surface. Bleached soil was once called brown Taijia forest soil and calcareous soil, distributed in the north-central Daxing 'anling and developed under the coniferous forest in the north temperate zone. Secondly, the surface layer is characterized by weak ashing or iron decoloration, often with bleaching layer, strong acidity and highly unsaturated alkali. It belongs to the transitional soil between grass quicklime soil and dark brown soil, and can be considered as a special soil cover influenced by local climate and vegetation.
Brown soil series soil is a very important forest soil resource. At present, there are not only a large area of natural forests for logging and utilization, but also the main forest production base in China. Moreover, most soils, especially yellow brown soil and brown soil distributed in hilly plains, have high agricultural value, and most of them have been cultivated as agricultural land and orchards.
Cinnamon series
Including cinnamon soil, Soil, black loessial soil and gray cinnamon soil, these soils accumulate humus in neutral or alkaline environment, and lime eluviates and deposits obviously, with different degrees of residual viscosity.
umber
Brown forest soil, also known as brown forest soil, is distributed in the semi-humid and semi-arid areas in the warm temperate zone of eastern China and formed under the mesogenic green forest. It is characterized by a brown clay layer under the humus layer, with low weathering degree, and the ratio of silicon to aluminum is 3.0 ~ 3.5. There are a large number of clay minerals such as hydromica and vermiculite under the clay layer, and lime accumulates in the form of pseudohypha. ?
Soil cinnamon soil is affected by long-term application of soil accumulation and tillage, and a mature layer with a thickness of more than 30 ~ 50 cm is formed in the upper part of the profile, that is, it becomes? Earth. Mainly distributed in Guanzhong area of Shaanxi Province.
Heirotu
Named after the dark and dark loess layer. The soil that first formed under semi-arid grassland vegetation and then matured after long-term cultivation is mainly distributed in the loess areas of northern Shaanxi, western Shanxi and eastern Gansu.
Grey cinnamon soil
Also known as grayish brown forest soil, it is soil distributed under mountain forests in arid and semi-arid areas, with dark brown or light brown clay layers. Due to different lime leaching degrees, it can be divided into two subcategories: grayish cinnamon soil and leached grayish cinnamon soil.
In terms of utilization, cinnamon soil system is an important forest land except gray cinnamon soil, and other soils are dry land in northern China. Soil and water conservation is an important measure to develop agricultural production.
Black soil series
The zonal soils in temperate forest grasslands and grassland areas in China include grey black soil (gray forest soil), black soil, albic soil and chernozem. Characterized by a large accumulation of humus.
Gray-black soil
Also known as gray forest soil. In humid areas, the western slope of Daxing 'anling is the most concentrated, with forest vegetation, lush undergrowth, vigorous grass growth process, large accumulation of organic matter, and obvious leaching and clay movement deposition in the soil.
black earth
The soil is rich in water and relatively humid, and the vegetation is grassland meadow, which is called "Wuhuatang" locally. The accumulation of soil organic matter is large, the soil layer is dark, the thickness of humus layer is more than 30 ~ 70 cm, and the lower soil often shows the characteristics of mild incubation.
baijiang soil
Under the surface humus layer, there is a gray-white slurry layer, hence the name. It is distributed in mountainous basins and valleys in the eastern part of Northeast China, with humid climate and shallow-rooted plants that like humidity. The accumulation of soil organic matter is not as good as that of black soil, and it often has peat characteristics because of poor decomposition of organic matter. The content of organic matter in the surface layer of albic soil is 8 ~ 10%, and the texture below albic soil layer is mostly heavy loam and clay. The white slurry layer is light in texture and the leaching loss of iron is obvious. Clay minerals are mainly hydromica, with a small amount of kaolinite and uncertain substances.
chernozem
Distributed in semi-arid areas, the vegetation is mainly grassland, and there are meadow grassland plants. The accumulation of organic matter is small, and the decomposition intensity is greater than that of black soil. Humus layer is generally about 30 ~ 40 cm thick. Lime leaching deposition in soil often forms powdery or pseudobacterial calcium deposition at 60 ~ 90 cm, which is an important feature that chernozem is different from other black soils.
Black soil series is the most widely distributed soil in Northeast China, which is suitable for developing agriculture, animal husbandry and forestry. In particular, black soil, chernozem and albic soil are important targets for developing agriculture. In addition to the cultivated land, there is a large area of wasteland for reclamation, which has great potential for agricultural production.
Chestnut soil series
Including chestnut soil, brown calcium soil and lime-lime soil, which are some grassland soils widely distributed in northern China. This kind of soil has obvious processes of humus accumulation and lime leaching-deposition, mostly weak gypsum and salinization. The soil formed under the hay in the semi-arid area of chestnut soil wet zone has chestnut or dark chestnut humus on the surface, with a thickness of 25-45 cm and an organic matter content of1.5-4.0%. Below the humus layer is a calcium accumulation layer, which contains a lot of gray-white variegated or powdery lime, and the lime content reaches 10 ~ 30%. The soil properties of chestnut soil in China showed obvious regional differences. Chestnut soil in the eastern part of Inner Mongolia Plateau has the characteristics of less humus, less salinization, less alkalization, no gypsum or deep gypsum layer, and weak viscosity. In the western part of Xinjiang, there are different amounts of gypsum and salt accumulation in the lower soil, and the humus content is high, but the soil is not alkalized and viscous.
Brown calcareous soil
Compared with chestnut soil, the accumulation process of humus is weak, while the accumulation process of lime is greatly enhanced. The location of calcium deposits generally rises in profile, formed in temperate desert grassland environment, mainly distributed in the central and western Inner Mongolia Plateau, the western Ordos Plateau and the northern Junggar Basin, and is a zonal soil for grassland to desert transition.
sierozem
Its formation is often related to the loess parent material, and its distribution area is most concentrated in the northwest of the loess plateau, the eastern part of the Hexi Corridor and the Ili River Valley in Xinjiang. The differentiation of soil profile is weak, and the occurrence level is not as clear as chestnut soil and brown calcium soil. The basic color of humus layer is light yellow-brown with gray, and calcium accumulation is not obvious. The content of organic matter in the surface layer is 0.5-3.0%, which extends downward deeply, generally reaching 50-70 cm.
Chestnut soil series is the main animal husbandry base in China and an important dry farming area. It is necessary to combine agriculture and animal husbandry, adjust measures to local conditions, improve grasslands, and establish artificial forage base.
Desert soil series
The important soil resources in the desert area of northwest China, including grey desert soil, grey brown desert soil, brown desert soil and cracked soil, are characterized by porous desert crust, low humus content, high lime content and strong surface agglomeration. Gypsum and soluble salts are accumulated at a small depth in the profile, with obvious residual adhesion and iron staining. The whole profile is thin and high in gravel content (except cracked soil and grey desert soil). In the process of soil formation, the main manifestations are calcification (lime accumulation), gypsum, salinization and weak iron, and the aeolian effect is quite obvious.
sierozem
The soil developed on the fine-grained soil at the edge of temperate desert is mainly distributed in the alluvial plain in the south of Junggar basin, the northern, middle and western sections of Hexi Corridor and the denudation plateau in the east of Alashan Plateau in Xinjiang. The organic matter content in the surface layer of grey desert soil in Xinjiang is about 65438 0.0%, and the humus layer is very inconspicuous. The highest lime content can reach 65,438+00 ~ 30%, and the aggregate appears below 20 or 30 cm. The maximum salt content of soluble salt is below 40 cm, which is often related to gypsum layer. The weathering of soil minerals is in the stage of potassium removal, and the ratio of silicon to aluminum is about 4.0. Hydromica is the main clay mineral.
Gray-brown desert soil
The soil and coarse bone matrix developed in temperate desert conditions occupy a large area in northwest China. Compared with grey desert soil, the accumulation of humus is weak, with less humus layers, and the organic matter content in the surface layer rarely exceeds 0.5%, and the content does not change much with the increase of depth. The ratio of carbon to nitrogen is very narrow, mostly between 4 and 7, but the lime content in the surface or subsurface layer is the highest, and gypsum accumulation is more common, which is 65433.
brown desert soil
The soil developed under the semi-shrub desert in warm temperate zone is widely distributed in southern and eastern Xinjiang. This kind of soil is basically adapted to the rocky desert or Gobi, similar to the rocky desert in North Africa (or gypsum desert and gypsum shell), but its drought degree is stronger, so that a chloride salt layer appears in the soil, which has become a rare phenomenon in desert soil in the world.
Cracked soil
Young desert soils are distributed in fine soil plains in temperate and warm temperate desert areas, and are often affected by short-term surface water flow. However, it does not have the nature of cement soil, its surface is flat, hard and gray, and it is cut into irregular polygonal lobes by network cracks, which looks like cracks embedded in the ground, which is its most representative feature.
The utilization of desert soil series is mainly controlled by the content of fine soil and the availability of irrigation water sources. At present, most of them are used for grazing, and only a few are used for cultivated land.
Tidal soil and irrigation silt series
The important agricultural soil resources in China include fluvo-aquic soil, irrigated silt soil and oasis soil. This kind of soil is formed under the influence of long-term cultivation, fertilization and irrigation. In the process of soil formation, a series of new properties were obtained, which greatly changed the accumulation of soil organic matter, soil texture and hierarchical arrangement, and salt profile distribution.
Tidal soil (including black soil in Jiang Sha)
Once known as light meadow soil, it is mainly distributed in the Huang-Huai-Hai Plain, the lower reaches of Liaohe River, the middle and lower reaches of Yangtze River and Fenwei Valley, and mainly grows wheat, corn, sorghum and cotton. On the soil profile, the sediment layer is obvious, the clay and sand alternate with each other, the groundwater level is shallow, and the redox interaction between the middle and lower layers of the soil has obvious rust spots and carbonate differentiation and accumulation. Some areas are flooded and salinized.
The mechanical composition of tidal soil in the Yellow River silting plain is mostly sand on the old riverbed and natural embankment, light loam on the flat slope on both sides of the old riverbed, and clay on the shallow depression. The content of soil organic matter is only 0.6 ~ 1%. The content of calcium carbonate is 6 ~ 8%, the content of potassium can reach about 2%, and the content of phosphorus is mostly 0. 1 ~ 0.2%. Its salt content generally does not exceed 0.1%; It can reach 0.5 ~ 1% at the edge of depression. The soil is alkaline, with a pH of 7.5 ~ 8.5.
Tidal soil is deep and rich in mineral nutrients, which is beneficial to the growth of deep-rooted crops. However, the contents of organic matter, nitrogen and phosphorus are low, which is prone to drought and flood disasters, and some areas have salinization problems, which need to be improved urgently.
Irrigation and siltation of soil
Mainly distributed in Yinchuan, Inner Mongolia Houtao and Liaoxi Plain. The thickness of the silt filling layer can reach more than 1 m, generally reaching 30 ~ 70 cm. The soil profile is homogeneous from top to bottom, with common cultural relics at the bottom. The buried surface of ancient farming can be seen under the irrigation and siltation layer. The physical and chemical properties of soil vary from region to region. The irrigated and silted soil in the West Liaohe Plain is relatively viscous, with an organic matter content of about 2-4%, a salt content of less than 0.3% and no gypsum. The irrigated and silted soil in Hetao area is loose in texture, with organic matter content of about 1% and high salt content.
Irrigation and silting soil is the main soil in the semi-arid plain of China, which is harvested once a year, mainly spring sowing crops, planting wheat, corn, millet and so on. Shallow groundwater level and abundant water resources; Due to poor drainage conditions, there is secondary salinization, so attention should be paid to the combination of drainage and irrigation.
Oasis soil
Also known as irrigated desert soil, it is mainly distributed in oases in desert areas of Xinjiang and Hexi Corridor, and is the main cultivated soil in arid areas. Irrigation siltation layer can even be as thick as1.0 ~1.5m; Irrigation and siltation layer in Kanerjing irrigation area shall not exceed 1 m.. The stratification of these thick irrigation and siltation layers is not obvious, and the organic matter content in the upper layer is generally 1 ~ 2%, and the lower layer can reach 0.5 ~ 0.7%. Phosphorus and potassium are abundant. The content of calcium carbonate is generally 10-20%, which is evenly distributed. But it is easy to harden and secondary salinization. The main ways to improve fertility are the combination of irrigation and drainage, the construction of windbreak belts and forest nets, reasonable rotation, and a variety of green manure and pasture.
Meadow and swamp soil series are wet soil. It belongs to aqueous and semi-aqueous soil types.
meadow soil
Directly infiltrated by groundwater, it develops under the cover of meadow vegetation. It is widely distributed in Songnen Plain and Sanjiang Plain, and also distributed in floodplains and lakeside terraces on both sides of rivers in Inner Mongolia and Xinjiang.
Meadow soil is generally rich in humus. The meadow soil distributed in northeast China has a black organic layer with a thickness of more than 1 m. Silicon powder is common at the bottom of soil, and rust-colored stripes and iron-manganese nodules can be seen in soil. In the meadow soil in Xinjiang, the organic layer is only 25 cm, and a large number of lime nodules are common, with salt accumulation. The content of surface organic matter is about 3 ~ 6%, even as high as 10%. In the depth of 1 m, its content can still reach 1%. In the arid area of northwest China, the content of surface organic matter is less than 4%. In the meadow soil of Xinjiang and Inner Mongolia, the content of calcium carbonate can reach 10%.
After the meadow soil was reclaimed, the surface soil became looser and looser, and the organic matter content also decreased. This kind of soil has high fertility, rich nutrients and good water supply, and is the main reclamation object; It is also an important pasture base, so it is very important to arrange the relationship between agriculture and animal husbandry reasonably.
everglade
It is formed under the condition of long-term water accumulation or excessive humidity. Widely distributed in Sanjiang Plain in Northeast China and Songpan Grassland in West Sichuan. There is a deep humus layer or peat layer.
Because the soil is in a state of reduction for a long time, there is an obvious incubation process and a fully decomposed blue-gray incubation layer is formed. The cohesiveness of soil is very low. In the surface organic layer or peat layer and the bottom blue-gray latent layer, a large number of soil layers with rust spots or gray spots can be seen, and iron-manganese nodules can also be seen. The organic matter content of swamp soil is usually 5 ~ 25%, and the peat layer can reach more than 40%. The decomposition of organic matter is insufficient and the ratio of carbon to nitrogen is wide. Most of them are not fully utilized. water
Paddy soil series
In China, it is mainly distributed in the south of the Qinling-Huaihe line, and the middle and lower reaches of the Yangtze River, the Pearl River Delta, the Sichuan Basin and the western plain of Taiwan are the most concentrated.
Paddy soil is the product of agricultural activities. It is made of various zonal soils, semi-hydrated soils and water-bearing soils by hydroponics. Under the influence of seasonal flooding irrigation, tillage, fertilization and other measures, the original soil characteristics have changed to varying degrees, and the profile has differentiated, thus forming a unique soil.
The profile structure of paddy soil includes the following levels: plough layer (a), plough layer (p), infiltration layer (w), sedimentary layer (b), sedimentary potential layer (Bg) and potential layer (g). When the tillage layer is flooded, it is saturated, semi-muddy or muddy. After being drained and dried, it has a massive structure, containing chips and fragments, and the surface of the structure is mixed with rust spots and plant residues; The bottom of the plow body is dense, with dark brown vertical structure, rust lines and small iron-manganese nodules; Due to the infiltration of water, the iron in the infiltrated layer has strong leaching property and light color; The sedimentary layers are mostly prismatic structures with many rust lines, rust spots and iron-manganese nodules. In the range of groundwater variation, the sedimentary hidden layer is gray-blue, with many rust spots and inconspicuous rust grain structure; The potential layer is in a reduced state and has a blue-gray structure. Paddy soil can be roughly divided into three types: submerged cultivation, water storage cultivation and latent cultivation. Submerged development layer is shallow, belonging to early paddy soil, and the underlying soil still shows the characteristics of parent soil, such as red soil still has a red bottom layer; The hatching type is well developed and the profile structure is complete; The type genus is developed from saprophytic soil or swamp soil.
Paddy soil is an important agricultural soil resource in China, which should be improved and fully utilized according to local conditions. Saline-alkali soil series can be divided into saline soil and alkaline soil.
salty soil
Saline soil with high soluble salt content in China is mainly distributed in arid and semi-arid areas in the north, especially in Inner Mongolia, Ningxia, Gansu, Qinghai and Xinjiang. North China Plain and Fenwei Valley are also dotted. The dry climate, strong evaporation, low terrain and underground salt water close to the surface are the main conditions for the formation of saline soil. The form of salt accumulation is usually white frost on the surface, which is distributed in patches. Salt crust thickness (less than 3 cm) or salt crust thickness (more than 3 cm) can be found in saline soil with high salt content, and loose salt-soil mixed layer can be found under salt crust or salt crust, and the thickness can reach several centimeters to 30 ~ 50 cm. You can even see the salt layer. Salt accumulation is characterized by strong surface aggregation and gradually decreasing salt content. Salt accumulation in coastal areas is characterized by high salt content in the whole soil.
The salt composition of saline soil in China is very complicated. Saline soil in coastal areas is mainly chloride saline soil; Sulfate soil is distributed in northern Xinjiang, Hexi Corridor in Gansu, Yinchuan Plain in Ningxia and Houtao area in Inner Mongolia, but the area is not large. Saline soil mixed with chloride and sulfate can be found everywhere in China, especially in Hebei, Inner Mongolia, Ningxia, Gansu and Xinjiang. In addition, the salt composition of Songnen Plain in Northeast China and Datong Basin in Shanxi Province contains carbonate, which is called soda saline soil, which is extremely alkaline and corrodes plant roots, making it difficult for most plants to grow.
Comprehensive measures such as irrigation and drainage, biology and tillage should be taken to improve saline soil; Planting rice and washing salt is also an effective measure to improve saline soil. The distribution area of alkaline soil in China is small, and most of them are scattered in saline soil areas. It is characterized in that the salt content in the surface layer is generally less than 0.5%, but the soil solution generally contains soda. In the absorption complex (especially in the alkaline layer), the substituted sodium accounts for more than 20% of the total substitution; The pH value can reach 9.0 or higher. The organic and inorganic parts of the soil are highly dispersed, and the colloidal particles and humus are leached downwards, which makes the texture of the topsoil shallow, while the alkalized layer accumulated by colloidal particles is sticky, sometimes forming a columnar structure, which swells when wet, shrinks and hardens when dry, and has poor permeability and arable property. Too high alkalinity will poison plant roots, and too much exchangeable sodium will cause a series of bad physical and chemical properties, which is very harmful to plant growth.
The formation and development of alkaline soil vary from region to region. For example, the alkaline soil in Songliao Plain is formed by sodium ions entering the soil absorption complex during the desalination process of soda saline soil. The alkaline soil in North China Plain (locally called brick alkali) is composed of salinized fluvo-aquic soil or saline soil. In the process of desalination, the alkalization characteristics of soil are prominent, and alkali shells appear on the surface. The former has high exchangeable sodium content (7 ~ 10 mg equivalent/100 g soil) and the degree of alkalization is mostly 20 ~ 40%. The latter is only 65,438+0 ~ 2 mg/65,438+000 g soil in light soil, and only 5 ~ 7 mg/65,438+000 g soil in heavy soil, which may belong to early alkaline earth. In addition to the above water conservancy and agricultural measures, chemical improvement measures such as gypsum and phosphogypsum are also needed to improve alkaline soil.
Lithologic soil series
Include purple soil, calcareous soil, phosphocalcareous soil, loessial soil (loess) and aeolian soil. This soil property still maintains the characteristics of parent rock or soil-forming parent material.
Purple soil
The soil grows on purple rocks. Sichuan basin is the most widely distributed, with sporadic distribution in the basins of southern provinces. The organic matter content of purple soil is about 65438 0.0%, which is slower than that of red and yellow soil in the same area and does not have the characteristics of desilication and aluminization. It belongs to weakly chemically weathered soil, with neutral to weakly alkaline reaction, pH value of 7.5 ~ 8.5, lime content varying with parent material, and alkali saturation of 80 ~ 90%. Purple soil is rich in mineral nutrients, which is fertile soil in hilly areas of Sichuan basin and has high agricultural utilization value. To prevent soil erosion, pay attention to water storage irrigation, increase the application of organic fertilizer, and rationally rotate crops. Lime (rock) soil is rock-forming soil developed on limestone. In the humid tropical and subtropical regions of China, limestone outcrops can be seen everywhere, but mainly distributed in Guangxi, Guizhou and Yunnan. Young lime (rock) soil is usually formed in karst areas where limestone bodies are exposed. The vegetation of calcareous (stony) soil is mostly calcium-loving plants such as fern, fern, thatch and so on. The organic matter of these plants becomes the material basis of calcareous soil humification. Lime (rock) soil can be divided into black lime soil, brown lime soil and red lime soil. ① Black calcareous soil, rich in organic matter, with good aggregate structure, dark soil color, neutral to alkaline reaction (pH 6.5 ~ 8.0) and different soil layers. (2) Brown calcareous soil, which is common on the slope of the foothills, is brown, sticky and has uneven lime reaction. (3) Red calcareous soil, bright red in color, with no lime reaction in the upper part, with topsoil pH of pH6.5 and core soil pH of 7.0 ~ 7.5. Phospholime soil is distributed in Dongsha, Xisha, Zhongsha and Nansha Islands in the South China Sea of China. Because these islands are located in the tropics, most of them are composed of coral reefs. Phospholime soil is developed on the basis of coral reef rocks, and its parent material is coral limestone or fine sand mechanically crushed by corals and shells. A large amount of phosphorus-rich bird droppings and organic matter accumulated on the surface of fine sand on the island, forming phosphorus-rich calcareous soil. The organic matter content in the surface layer can be as high as 12%, and the total phosphorus content is 26 ~ 32%. Become a natural phosphate fertilizer resource rich in organic matter.
loess
Also known as loess, it is widely distributed in hilly areas in the middle reaches of the Yellow River. The soil color is very close to the parent material layer, with uniform texture, porosity, good arable property, low organic matter content, only 0.5%, and rich mineral nutrition.
Aeolian sandy soil
Mainly distributed in semi-arid, arid and extremely arid areas in northern China. The characteristic of aeolian sandy soil is that the soil-forming process is often subjected to wind erosion and sand pressure, which is very unstable, resulting in a very weak soil-forming process and little change in soil properties and aeolian deposits. With the natural fixation of sandy land and the development of soil formation stage, from mobile aeolian sandy land to semi-fixed and fixed aeolian sandy land, the content of soil organic matter gradually increased, indicating that vegetation can grow stably and can also become land for agriculture, forestry and animal husbandry as long as fertilizer and water are added. Alpine soil series Alpine soil refers to the soil in the Qinghai-Tibet Plateau and similar altitude, the uppermost part of the alpine vertical zone, above the forest canopy line or in the forestless alpine zone. Due to the alternation of freezing and thawing in the alpine region, the degree of soil organic matter humification is low, the decomposition of minerals is also weak, the soil layer is shallow, the coarse bones are strong, and the grade differentiation is not obvious. Therefore, alpine soil is divided into a unique series; There are black felt soil (subalpine meadow soil), grass felt soil (alpine meadow soil), Baga soil (subalpine steppe soil), Shaga soil (alpine grassland soil), alpine desert soil and alpine cold desert soil.
Black felt soil
Mainly distributed in the eastern and southeastern parts of the Qinghai-Tibet Plateau. Humus accumulates obviously, humification degree is high, base is unsaturated or saturated, and pH value is 5 ~ 8. It is an excellent pasture on the plateau and a high-yield soil for wheat and other crops.
Grass felt soil
It is distributed on the hillside with gentle surface in situ, with generally moist soil and dense alpine meadows. The surface layer has turf with a thickness of 3 to 5 cm to 65,438+00 cm. The root system is felt-like, light, tough and elastic. Due to the interaction of freezing and thawing, the surface is often scaly. The thickness of humus layer is 9 ~ 20 cm and its content is 6 ~14%. Light grayish brown or dark gray, with a section thickness of 30 ~ 40 cm. Mostly used as summer pasture.
Bagatu
It is mainly distributed in the plateau wide valley lake basin on the north side of the Himalayas, and the vegetation belongs to grassland type. The content of soil organic matter can sometimes reach 3 ~ 10%, and film-like calcium carbonate is often accumulated on the back of gravel at the lower part of the profile. Most of them are pastures with sparse vegetation and low livestock carrying capacity.
Shagatu
Distributed in the southeast of Qiangtang Plateau and in front of the western Himalayas. When the soil is dry, the process of humus accumulation is weakened and calcium accumulation occurs. The soil is rich in gravel, with few grass roots on the surface, and no continuous turf layer has been formed. The content of organic matter is about 1.5 ~ 3%, and the accumulation of calcium carbonate is obvious, and the maximum can reach more than 10%. The soil is sandy, and the wind and sand are harmful, all of which are pastures.