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Classification and kinds of soil


Classification and kinds of soil
Soil Classification means the classification of soil in orderly systematic groups by compilation of various kinds of soil having similar characteristics or properties as determined to be classified in the same group for the convenience in the application and simple to remember with the objectives, namely:
1.
 To compile various knowledge about soil characteristics in groups or classes.
2.
 To show the relation of various kinds of soil and to promote the more understanding about various kinds of soil and learn the new principle and relation about the soil.
3.
 To be able to remember various characteristics of soil easier.
4.
 To distribute the soil kinds reasonably into groups or classes and it is useful for the soil behavior forecast, determination the most appropriate utilization of a soil, estimation of production yield from a soil and soil unit from the classification will be the basic unit in a research and to transfer knowledge and technology on the soil science.
 
Soil classification cane be divided into 2 categories, namely:
1.
 Pure soil classification (Comprehensive Natural or Taxonomic Classification) is the soil classification relying upon the physical and chemical characteristics and properties of soil including the soil forming environment as the norm. This type of soil classification is widely popular in the soil survey and map making and used as the database in the applied soil classification.
2.
 Applied soil classification (Interpretive or Technical Soil Classification) is the soil classification relying upon the soil survey data, soil map making and pure soil classification as the norm in the consideration and classification of soil into various groups for the benefits of land utilization in each objective which may be called that it is the result of soil survey interpretation.
 
The soil classification system used in the survey to make the soil map of Thailand is as follows:
1.National soil classification system
               The national system herein mentioned is the soil classification improved by Mr. R. Dudal and Dr. F.R. Moorman from the soil classification system of the United states Department of Agriculture (1938). Its most part has close various criteria but there are some parts changed and added to suit the soil conditions in Southeast Asia that Thailand used to apply such system as the national soil classification system for a period.
               The main concept of this system regarded that the zone of climate and vegetation are very important factors the results the soil to have different characteristics. In this system, there is the structure consisting of the high or advanced and low classifications whereas the high classification consists of the order, suborder and great soil group but the low classification consists of the family, series, type and phase. In Thailand, the order or suborder classification is hardly used; the mostly used classification is the great soil group and downward.
 
Various principal soil groups of Thailand categorized according to the national system as follows:
1. Regosols
               These are soils formed on beach and sand dune and show little or no profile development. They are found along or near the coastline, usually in elongated strips. Regosols on recent dunes and beaches have, at most, a weekly humiferous surface horizon, resting immediately on yellowish to brownish sand. The soil material ranges from very fine sand to moderately coarse sand.Regosols on somewhat older dunes and beaches situated at some distance from the present coastline have a more distinct humiferous surface horizon. The sand is very fine to medium and composed almost exclusively of quartz grains; calcium carbonate is leached from the surface layers, frequently to a considerable depth.Locally, regosols are found on older fine sands with a reddish to yellowish red subsurface color. The red color is caused by ferruginous coating of the individual sand grains.
2. Alluvial soils
               Alluvial soils are young soils, formed on recent water-deposited materials; they usually show little profile development other than a humiferous surface horizon and ferruginous mottling due to periodic high ground water. These soils are found in plains and valleys throughout the country.The large majority of alluvial soils in Thailand are composed of clay; a few percent have a loamy texture, whereas sandy Alluvial soils are rare. Soils with alternate clayey, loamy or sandy layers occur, especially in narrow stream valleys.
3. Peat and Muck soils
               The only extensive areas of soils composed for an important part of organic material occur in the southeastern coastal area of Peninsular Thailand, closed to the Thai-Malayan border. These are coastal peats, typical of the low land of the wet tropics. Depth of the peat varies from 30 cm to several meters. At least, part of the Peat and Muck soils has developed under brackish water conditions. Consequently, they may be potentially acid to very acid, with a high sulphur content.
4. Low-Humic Gley soils
               Low-Humic Gley soils are predominantly formed on older alluvial sediments, thus they are typical soils of the various alluvial terraces in the lower areas. Mostly, the topography of these soils is flat, but locally they may occur on gently sloping or undulating relief.These soils are characterized by signs of wetness (gleying) throughout the profile or starting immediately below the surface horizon. They also have in common subsoils with contain more clay than the surface soil, due to the formation of a textural B horizon. Texture of these soils ranges from considerably, from clay throughout to loamy sand or even sand at considerable depth.
5. Grumusols
               These soils are found on rich, clayey parent materials of varies origin. Most commonly, these materials are associated with limestone, marl and limestone derived alluvium. Less important in extent are Grumusols on materials derived from basic igneous rocks (basalt and some andesite). Most Grumusols are in the flatter, depressed areas, but those on basalt may occur in a distinctly undulating landscape.Characteristically, Grumusols are composed of heavy clay in with montmorillonite is an important clay mineral. Most commonly, the surface layers are black or very dark grayish brown to a considerable depth, i.e. 40 cm or more. When dry, these soils are crack deeply, the width of the cracks often being well over 3 cm. When under paddy, the surface of the land is usually smooth, but outside the paddy fields, the land shows and irregular surface (gilgai relief). In the soil profile, slickensides can be observed.
6. Renzinas
               Renzinas are formed almost exclusively on very calcareous materials, mainly marls and weathered fragments of hard limestone. Consequently, these soils occur mainly in association with limestone areas. Renzinas were observed on highly basic and calcareous weathering products of basalt. The relief of Renzinas is normally undulating, sometime rolling. They occur in close association with Brown Forest soils.A typical Renzinas show a black or very dark brown surface layer, passing at varying depth (usually less than 0 cm) to the subsoil which contains 50 percent or more calcium carbonate. Free lime is usually found throughout the profile, though the top layer may have been slightly leached. The surface soil is clayey to loamy, with a crumb structure and an excellent tilth.
7. Brown Forest soils
               These soils are formed on a wide variety of parent materials throughout the country. Small scattered spots of Brown Forest soils, too small to be indicated on the map, are found on steep slopes and on slope colluvium. Some of the better drained soils on river alluvium, notably on river levees of some age, show weakly developed Brown Forest soils profiles. Somewhat larger consolidated areas occur in association with Renzinas on calcareous parent materials. The latter soils are mentioned in the legend.These soils are medium to fine textured and show high base saturation throughout. pH values are 6-7 in the surface layer, and 8 in the sub soils.
8. Noncalcic Brown soils
               These soils are formed on semi-recent alluvium and are mostly associated with moderately to highly saturated Low-Humic Gley soils. Their topography is flat to slightly undulating.Noncalcic Brown soils have a loamy to clay texture, silt loam to silty clay loam being common. The subsurface texture is finer than that of the surface layer, due to the formation of a textural B horizon. No signs of wetness (mottling) occur in the surface layers, but the subsoils may be mottled. Colors are brownish in the top soil and strong brown, yellowish brown and reddish yellow in the subsoils. Most Noncalcic Brown soils have a medium to high base saturation which increase in the subsoil. Correspondingly, the pH of many of these soils is near neutral at some depth, with free lime being present occasionally.
9. Red-Brown Earth
               These soils are associated with basic rocks, mainly with limestones and to a much lesser extent, with basalt. They are formed on residuum and colluviated residuum from limestone and basalt, and on alluvial and colluvial deposits which are derived largely from limestones. Their topography is mostly undulating to gently rolling, but maybe steep close to or on limestone crags. These soils do not, or only rarely, occur in the high rainfall areas of the country. Red-Brown Earths commonly have a clayey texture throughout the profile, the surface soil containing less clay than the subsoil. The color of the subsurface layer is characteristically dark red to dark reddish brown. Base saturation is medium to high, increasing usually in the subsoil where free lime may be present. Soils with a lower subsoil base saturation and, consequently, a lower pH, are transitional to Reddish-Brown Lateritic soils. The soils usually show no sign of wetness, but mottling may be found in the subsoil of the lower members of the group.
10. Gray Podzolic soils
               These great soil group is found extensively on terraces of the major rivers and streams and, to a lesser extent on coastal terraces of the southeast coast and the east coast of Peninsular Thailand. The most extensive occurence of these soils is on the Northeast Plateau where Gray Podzolic soils dominated in the areas and slope colluvium of acid rocks, e.g. acid granite.Gray Podzolic soils show a rather uniform profile with gradual transitions between the subsurface horizons. The illuvial or Bt horizon contains more clay than the surface A horizon, but frequently this difference can be determined only by laboratory analysis. Sandy Gray Podzolic soils have a very week horizon differentiation. The majority of these soils have a medium texture, sandy loam or loamy sand in the surface, and sandy loam to loam in the subsoil. The soils are excessively to moderately well drained and do not show distinct sign of wetness in the upper layers.
11. Red-Yellow Podzolic soils
               This is a very widespread Great Soil Group in Thailand? developed from a wide range of parent materials, i.e. weathering product from intermediate to acid rocks and older alluvial sediments, provided the latter are not too strongly leached. Red-Yellow Podzolic soils occur on diverse land forms, but the majority are founded in the highly parts of the country.The Red-Yellow Podzolic soils commonly show a distinct horizon differentiation in the profile. The subsurface horizon (Bt) have considerably more clay than the surface horizons, which usually have a loamy texture. Admixture of rock fragments is common on all sloping soils, and the steeper members are mostly very stony and/or rocky. The degree of stoniness is further related to climate; soils in the drier parts are usually shallower and more stony than soils on similar parent materials and slopes in the high rainfall zones.
12. Reddish-Brown Lateritic soils
               These soils have mainly been developed from residuum and colluvium from intermediate rock. Finally, these soils are found to a limited extent on old alluvium where the rocks of the adjacent catchment areas are basic.Reddish-Brown Lateritic soils mostly have a clayey texture throughout the profile, though the upper horizons may be loamy or locally, even sandy. When developed on residuum, admixture of rock fragments is common. A distinct textural B horizon (Bt) is observable. The color of the subsurface horizons is characteristically dark red to dark reddish brown. At greater depth, mottled clay, with or without laterite, may be found. This layer is of increasing importance toward the higher rainfall zones. The soils show no signs of wetness in the upper horizon, but mottling may be found in the lower members of the group, especially in the rainfall zones.
13. Reddish-Brown Latosols
               Reddish-Brown Latosols occur on basalt formations. This area has an undulating to gently rolling relief. They are deep clay soils, with a weakly developed A horizon and a dark reddish brown subsoil which remains uniform in color and texture to a great depth. Physical characteristics of these soils are excellent; they are friable, very porous and permeable, resulting in deep and unhampered root development. Base saturation of the subsurface horizons is medium to low, with pH values from 5.5 to 6.5. The inherent fertility of these soils is in fair.
14. Red-Yellow Latosols
               Red-Yellow Latosols have deep to very deep profiles which, below the surface layers, show a red to yellowish red color without any visible signs of wetness. The texture is commonly rather sandy clay loam to sandy clay in the red subsoil. Frequently, the surface layers show signs of degradation, the fine soil particles being leached down; this may lead to the formation of an A1-A2 horizon sequence. The underlying B horizon, however, is not to be considered as a horizon of clay accumulation (Bt).
15. Humic Gley soils
               Humic Gley soils occur regularly in valleys of creeks where basic rocks, mainly limestone, are an important element in the catchment area. Besides, Humic Gley soils were observed in spots in the marine part of the Chao Phraya Delta, Central Plain.These soils normally have a loamy to clayey texture. They are characterized by a dark gray to blackish colored Ap horizon of at least 25 cm thick, with an organic matter content of over 1.5 percent, and having a crumb structure. Base saturation in this horizon is medium to high, usually increasing with depth. The subsoil frequently is calcareous. Signs of wetness are masked by the dark color of the A horizon, but the soils are wet or even inundated during most of the rainy season.
16. Solodized solonetz
               These are soils developed on originally saline terrace deposits in the drier parts. These soils show a sandy to loamy, leached surface horizon, overlying a very hard and impermeable Bt horizon composed of clay or sandy clay with a characteristic columnar structure. Salt, if present, is found mainly in the subsoil.
17. Ground Water Podzols
               These soils are found on quartzitic beach and river-terrace sands in high rainfall zones. Below a dark gray surface horizon, a light gray leached A2 horizon is usually found, which is underlain by a blackish to dark brown horizon of humus accumulation (Bh) at varying depths. These soils are periodically water saturated.
 
2. Soil Taxonomy
               The soil taxonomy is the soil classification system prepared by some soil scientists of the United States Department of Agriculture by using USDA1938 as the base in soil classification improvement to have conciseness or precision and can be utilized more. Thailand started to adopt this soil taxonomy for experimental application coupled with the old soil classification system approximately in 1967. Later it had been considered as the suitable one, it was therefore applied as the national system until present with the following reasons, namely:
1)
 It is the system having procedure of perfect classification as same as the plant and animal classification which is divided into 6 levels including order, suborder, great group, subgroup, family and series.
2)
 The names of soil series categorized from the order to the family have the meaning in themselves and indicate the soil significant characteristics as categorized.
3)
 The soil characteristics used in the classification of each class are rather quite certainly determined, can be measured and examined in both in the field and in laboratory that are the soil characteristics that are rather certain , firm and not easily changeable.
4)
 It is the soil classification that can be brought the classification result to be used in the exchange of agricultural technology very well applicable at national or regional level especially the family soil classification.
5)
 It is a system with wide objective that can diagnoses the classified soil quality for application in many categories purpose.
 
The soil in Thailand can be classified according to the soil taxonomy into 9 orders from total 12 orders as follows:
1) Alfisols
               This soil has moderate development to rather good level, having characteristic of clay accumulation in the sublayer. Its general characteristics are similar to those of soil in Ultisols order but the difference that the Alfisols has less development and leaching that the base elements still remain very much in the soil cross section , especially the lower layer and there is more than 35 percent base saturation. This soil order is always found at the surface soil in the rather new terrain. The area is stable for quite a long time without soil disturbance under the humid climate enough to cause various material movement within the soil but simultaneously, it must be dry enough to limit the movement of base material not to be removed out of the soil surface. We will not find this soil in the vicinity of very steep slope that is the alluvial plan and in the low basin with very bad drainage.
               In Thailand, we can found this kind of soil in wide vicinity, both in lowland and highland, especially in not frequent rainy zone that the humidity between the rainy and dry seasons is concisely different. The soil feature is brown or brownish red but it is possibly to be found in yellow, red dark or gray. The soil mass texture appears in many types but the important feature, it must show the nature of accumulation of clay particles in the criteria being Argillic sub-layer in the soil sub-base layer.
2) Entisols
               Entisols is the soil having characteristics that shows it has no development or just a little development of soil layer that may result from too short time for development or it is in the very steep vicinity having forming deterioration all time or may be in the lowland influenced by accumulated sedimentation quite frequent that the soil layer cannot be developed.The entisols found in Thailand can be found in many characteristics both in the lowland and highland possibly divided into 4 features according to the soil forming environment,
as follows:
 Entisols in the marsh lowland subject to the sea tide fluctuation influence.
 
 Entisols arisen from alluvium in the flood plain, natural water channel bank bar and alluvial fan dune.
Pure sand entisols exists in the vicinity where the forming material is pure sand such as sand dune, sand bar generally found both in the continental and coastal vicinities.
Entisols existing in the very steep slope mountain shoulder vicinity that has high opportunity to deterioration in the accelerating rate that the soil development has not enough time to create a distinguish characteristics. Regular loss of soil surface made the found soil’s characteristics to be a shallow soil, the soil content texture always consists of gravel and mixed with the small rock of parent material.
3) Inceptisols
               Inceptisols is the soil that has just had the development having both physically and chemically changing processes arisen but various accumulation is not sufficient to cause any outstanding decidable soil layer as the soil that had passed lengthy development. At its surface, an ample of parent material residues, this soil is always found at the vicinity where the soil parent material has high resistance to the change or the topographic condition has high restrictions such as the very steep slope or the low basin, not stable sufficiently to have the development of the formation layer continuously arisen. Inceptisols in Thailand may be found in both the lowland and highland but it has wide area in the lowland especially in the vicinity of central plain.
4) Vertisols
               Vertisols is the dark soil consisting of clayish ore that has high elasticity and plasticity when the moisture content changes that causes cracking texture at its surface during the dry season. Within its sub-layer, we can find the slickenside that has glossy smooth surface at the soil mass due to the soil’s elongation and shrinkage. In the rainy season, the rain enables the upper soil surface will move along the cracks and cause mixing of the upper and lower soil so called “self mulching”. An important feature is the surface of topographic conditions of this soil area has tendency to be gilgai relief and has the upper structure as the porous ball so called “crumb structure”. The soil of this order arises from the parent material mostly having base reaction so it has high pH value or being alkaline in its sub-layer. In general, there is hardly problem on its fertility but there may be problem due to its being too clayish and cracking at its surface is crucial obstacle to usage of mechanical tools in the field when it is wet.Vertisols in Thailand was found in not so wide area, most of them is in the central plain, central high mountainous range, the high plateaus of the northern and northeastern parts of Thailand limited in the vicinities where the parent material has high base content or in the vicinity influenced directly from the base reactive rocks such as limestone, marl, basalt and andecites.
5) Histosols
                Histosols is the soil having the forming characteristics and general properties very much different from the soil in other orders because it is the soil arisen from the accumulation or sedimentation of organic matters in the environment of closed low basin, continuously or nearly continuously inundated or it may be arisen in the steep slope vicinity or capillary water alignment that sufficiently supplies water to cause the conditions to block the oxidation to occur with the soil that the degradation or decadence process that changes the minerals of organic material arisen slower than the organic matters accumulation process that originates into the thick accumulation layer whereas the accumulation firstly occur from the lower layer to the upper layer. Hence, Histosols is the soil unlimited by the climate or the deeper layer previously existed but it is limited by the soil parent material that must be the organic matters only.The outstanding feature of the soil of this order is it is the soil having high content of organic composition when compared with the mineral composition in the soil. Its normal organic carbon content is more than 200 grams per kilograms. In physical nature, it is classified to be the soil of high capacity to bear water. The water in the soil, both in the big and small voids that plants difficultly absorb water to use. In general, it is alike the sponge which can receive the input water and release the water out, it can very much contract itself when dried, having high porosity and low density. In the status of no land usage, the organic matters will remain in the previous characteristics for a long time but if there is water drainage out and there is land utilization, the decadence rate is very rapid, the organic matters would easily be lost and the severe acid soil may be arisen.
6) Spodosols
               It is the soil consisting the ash-like gray sand layer having acid reaction, laying itself on top of dark or dark red sandy loam layer arisen from the accumulation of degraded organic matters and aluminum oxide and / or ferrous oxide that is the specific feature of spodic horizon lower layer and this is the important characteristic that makes this Spodosols order different from the other soils.This soil always occurs in the frequent or rather frequent rain vicinity that has sufficient water quantity to cause movement of material from the topmost of soil surface to be accumulated in the bottom layer and moreover, there must be organic matters and pure sandy parent material that may be the old beach of a river or sea and it may be found sometimes at the vicinity of steep slope. In Thailand, the land covered with this soil is very rare , most of them scattered around the southern part, southeastern coast and the upper part of the northeastern region especially along Mekong River.
7) Mollisols
               Mollisols is the topmost soil layer or thick soil surface pertaining dark to black colour, having a good soil structure, consisting of high content of organic. The soil mass is friable or loose, giving tender feeling when touched. It may be found both in the lowland and highland especially in the vicinity where the soil parent material can deteriorate to yield the high base elements. The natural vegetation is grassland, under the climate sometimes having dry interval that does not promote the continuous washing process so there are ample remains of the base positive charge elements in the soil cross section. In general, it is the not much developed soil. In Thailand, this kind of soil was so few quantity found, limited scope within only the vicinity of the parent material source having reaction of alkalinity. Most of them have soil mass content as a clayish to very clayish soil, good structure, good infiltration at the soil surface in the highland but can trap the water in the lowland, the soil can very well bear water. Mollisols found.

Thailand can be divided into 3 groups as follows:
 Mollisols arisen in the swamp vicinity previously subject to the fluctuation of sea tide and arisen from the alkaline sediment.
Mollisols found at the vicinity of high mountainous range in the central part of Thailand.
Mollisols that has Calsic layer deeper than 1 meter, found in the vicinity of high mountainous range in the central and northern parts.
8) Oxisols
                Oxisols is soil having accumulation of ferrous oxide and aluminum oxides so called sesquioxides in high content arisen from severe degradation process at site or lengthy passing the soil forming process. The significant characteristics of soil in this order is bright red, yellow or gray soil, the soil mass texture is rather clayish or pure clay but it has very good structure, highly friable and loose soil and very consistency within the soil cross-section, namely it has various similar characteristics throughout the soil cross section that makes the distribution of soil forming class is difficult. The main components found in most soil are substances having low activities such as quartz, kaolinitic clay, ferrous oxides , aluminum oxides and organic matters.In Thailand, this soil was dispersedly found in very few area, most of them are in the vicinity of eastern rim of the southeastern coast and some areas in the northeastern part, namely Nakhon Ratchasima, Si Saket and Ubon Ratchathani.
9) Ultisols
               Ultisols is the soil having distinguish characteristics that shows the soil has long development in the condition that its parent material has passed at site degradation, washing away, various material movement process continuously for a long time that causes the outstanding clay accumulation at substratum and the soil is saturated with alkaline positive charges lower than 35 percent and decreasingly according to the depth.
                Ultisols was found in the widest vicinity in Thailand whereas it was found ample in the northeastern part of Thailand, southeastern coast, southern part and prevalently found in the central and northern parts, both in the highland and lowland. In general, the deep soil may be red or yellow in the highland and scattering spots gray soil in the lowland. The soil content texture can vary a lot from clay, friable, loose and sandy and some kinds may have gravels in the soil content and there may be plintite layer at various depths.
 
3. 62 Soil Series Groups
               Soil series group is the soil classification unit prepared by combination of soil kinds according to the soil series classification in Soil Taxonomy System that have similar physical and chemical characteristics and have similar utilization potential into the same group that 62 groups are classified (consisting of 59 soil series group and 3 other units are the combined soil unit according to the topography). This classification system firstly occurred approximately in 1987 while the Soil Survey and Classification Division was having project to improve 1:50,000 soil provincial map and the map preparation reporting the provincial land utilization for the economic plants cultivation throughout the country. This project had objective to facilitate in bringing data for the promotion, transferring knowledge to agriculturists or planning land utilization that is appropriate to the land potential.
All 62 soil series groups can be divided according to the found areas in 4 characteristics as follows:
1.
 The soil series group in swamp area or the water trapped area, this type of land can be found in all regions, including the 1st -25th soil series groups and 57th -59th soil series groups.
2.
 The soil series group in highland in the dry soil area, this type of land can be found in the central, northern and northeastern regions, including soil series groups No. 28, 29, 30, 31, 33, 35, 36, 37, 38 ,40, 41, 44, 46, 47, 48, 49, 52, 54, 55, 56, 60 and 61.
3.
 The soil series group in highland in the moisturized soil area, this type of land can be found in the south and southeastern regions, including soil series groups No. 26,27,32,34,39,42,43,45,50,51 and 53.
4.
 The soil series group in high steep slope, this type of land can be found in the hilly area and mountainous range of over 35 percent slope, including soil series groups No. 62.
Soil Series
Group No.
Distinct Characteristics
Soil Series
Soil in swamp area with water trapped
1
 Very deep black clay, wide and deep cracking marks at its surface, soil reaction is a little acid to a little base, bad to rather bad drainage. Ban Mi (Bm),
Ban Pod (Bp),
Buri Ram (Br),
Chong Kae (Ck),
Kok Kratiem (Kk),
Wattana (Wa)
2
 Very deep black clay group, soil reaction is very acid, may find pale yellow spots of sulfates deeper than 100 cm. from the ground surface, bad drainage, moderate fertility. Ayutthya (Ay),
Bang Khen (Bn),
Bang Nam Prieo (Bp),
Maha Phot (Ma)
Tha Kwang (Tq)
3
 Very deep black clay group, arisen from the blackish sediment, may find the mud layer of sea water sediment without potential to form sulfuric acid soil within 150 cm. depth from the ground surface, soil reaction is neutral to alkaline (base), bad drainage, moderate to high fertility. Bangkok (Bk),
Bang Len (Bl),
Bang Phae (Bph),
Chachoengsao (Cc),
Samut Prakan (Sm)
4
 Very deep clay group arisen from distributaries sediment of short period, soil reaction is neutral to alkaline (base), rather bad drainage, moderate fertility. Bang Mun Nak (Ban),
Bang Pa-in (Bin),
Chai Nat (Cn),
Pimai (Pm),
Ratchburi (Rb),
Saraburi (Sb),
Singburi (Sin),
Sri Song Kram (Ss),
Tha Pon (Tn),
Tha Rua (Tr)
5
 Very deep clay group arisen from distributaries sediment, soil reaction is neutral or alkaline (base), bad drainage, low to moderate fertility. Hang Dong (Hd),
La Ngu (Lgu),
Phan (Ph)
6
 Very deep clay group arisen from distributaries sediment, soil reaction is very acid to pure acid, bad to rather bad drainage, low fertility. Bang Nara (Ba),
Chiang Rai (Cr),
Su Ngai Kolok (Gk),
Klang (Kl),
Klong Kut (Kl),
Manorom (Mn),
Nakhorn Panom (Nn),
Pak Thor (Pth),
Pawong (Paw),
Patalung (Ptl),
Satul (Stu),
Tasala (Tsl),
Wangtong (Wat)
7
 Very deep clay group arisen from distributaries sediment, soil reaction is neutral to base, rather bad drainage, moderate fertility. Doembang(Db),
Nan (Na),
Nakhon Pathom (Np),
Pak Kat (Pat),
Suko Thai (Skt),
Tatum (Tt),
Uttaradit (Utt),
Ra Nod (Ran)
8
 Soil series group having grooves dug and parapets elevated to change the land utilization from the rice field to vegetable beds or orchards that result in irregular soil characteristics and properties in each area depending on the previous soil characteristics and properties before the surface deformation and procedure of planting bed preparation. Damnoen Saduak (Dn),
Samut Songkhram (Sso),
Thon Buri (Tb)
9
 Very deep clay group, arisen from sea water sediment which is very salty and sour, the topsoil reaction is very severe acid, substratum reaction is neutral to base, bad drainage, low to moderate fertility. Cha-am (Ca)
10
 Shallow sour soil group, arisen from sea water sediment, the soil reaction is very severe acid, bad drainage, low fertility. Chian Yai (Cyi),
Mu Noh (Mu),
Onkarak (Ok)
11
 Moderate deep sour soil group, arisen from sea water sediment, the soil reaction is very severe acid, bad drainage, low fertility. Don Muang (Don),
Sena (Se),
Tanya Buri (Tan)
12
 Seaside salty mud soil group, without potential to form the sulfuric acid soil, the soil reaction is neutral to base, very bad drainage, moderate to high fertility. Ta Chin (Tc)
13
 Seaside salty mud soil group, with potential to form the sulfuric acid soil, the soil reaction is neutral to base, very bad drainage and moderate to high fertility. Bang Pakong (Bpg),
Ta Kua Tung (Tkt)
14
 Moderate deep sour soil group having mud layer that has potential to form very sour soil or sulfuric acid soil within 150 cm. from the ground surface, the topsoil reaction is very severe acid and the substratum reaction is a little acid to base, bad drainage and low fertility. Pattani (Pti)
Ra Nga (Ra)
Ton Sai (Ts)
15
 Very deep siltstone sandy soil group arisen from the distributaries sediment, the soil reaction is neutral or base, bad to rather bad drainage, low to moderate fertility. Lom Sak (La),
Maesai ( Ms),
Mae Ta ( Mta)
16
 Very deep siltstone sandy soil group arisen from the distributaries sediment, the soil reaction is very acid, bad drainage, low fertility. Hin Kong (Hk),
Koh Yai (Koy),
Lampang (Lp),
Phan Thong (Ptg),
Sri Thep (Sri),
Tak Bai (Ta)
17
 Very deep fine loam soil group arisen from the distributaries sediment, the soil reaction is very acid, bad to rather bad drainage, low fertility. Bun Tarik (Bt),
Sai Buri (Bu),
Kem Marat(Kmr),
Kok Kien (Ko),
Lom Kao (Lk)
Su Ngai Padi (Pi),
Pak Kom (Pkm),
Roi Et (Re),
Renu (Rn),
Song Kla (Sng),
Visai (Vi)
18
 Very deep fine loam soil group arisen from the distributaries sediment, the soil reaction is neutral to base, bad to rather bad drainage, low to moderate fertility. Chon Buri (Cb),
Chai Ya (Cya),
Kok Samrong (Ksr),
Kao Yoi (Kyo)
19
 Very deep coarse loam soil arisen group from the distributaries sediment with dense layer within 100 cm. depth from, the soil reaction is very acid to little base, rather bad drainage, low fertility. Ma Kham (Mak),
Wichen Buri (Wb)
20
 Very deep siltstone sandy soil group arisen from the distributaries sediment, the soil reaction is neutral or base, bad to rather bad drainage, low to moderate fertility. Kula Ronghai (Ki),
Nong Kae (Nk),
Tung Sumrit (Tsr),
Udorn (Ud)
21
 Very deep coarse loam soil group arisen from the distributaries sediment at the low part of the river bank, the soil reaction is a little acid to neutral, rather bad to rather good drainage, moderate fertility. Phetchaburi (Pb)
Saphaya (Sa)
22
 Very deep coarse loam soil group arisen from the coarse sand distributaries sediment, the soil reaction is very acid to neutral, bad to rather bad drainage, low fertility. Num Krachai (Ni),
Sansai (Sai),
Sri Thon (St)
23
 Very deep sandy soil group arisen from the seaside sediment, the soil reaction is little acid to neutral, bad drainage, low fertility. Bang Lamung (Blm),
Sai Khao (Sak)
Wang Prieng (Wp)
24
 Very deep sandy soil group arisen from the distributaries sediment that the soil mass is the thick sand layer, the soil reaction is acid, rather bad to rather good drainage, low fertility. Ban Bung (Bbg),
Ta Utain (Tu)
Ubon (Ub)
25
 Shallow soil group, the soil reaction is very acid to little base, bad to rather bad drainage, low fertility. Kan Tang (Kat),
On (On),
Phayom Ngarm (Pym),
Sa Ton (Stn),
Tung Khai (Tuk),
Yan Ta Khao (Yk)
57
 Soil group having organic material thicker than 100 cm. from the ground surface lying upon the seawater sediment, the soil reaction is very acid, very bad drainage, low fertility, nearly all year-round inundated. Kab Daeng (Kd)
58
 Soil group having organic material thicker than 100 cm. from the ground surface, the soil reaction is acid, very bad drainage, low fertility, nearly all year-round inundated. Naratiwat (Nw)
59
 Coarse or fine loam soil group arisen from the complex alluvial sediment, soil layers have alternative lamination, the soil mass in uncertain , depending upon the accumulated sediment, the soil reaction is very acid to neutral, bad to rather bad drainage, low fertility. AC-pd: Alluvial Complex, poorly drained
28
 Very deep black clay soil group , deep and wide cracks when dry, soil reaction is neutral to base, good to moderate good drainage, moderate to high fertility. Chai Badan (Cd),
Dong Lan (Dl),
Lop Buri (Lb),
Nam Len (Nal),
Wang Chompoo (Wc)
29
 Deep to very deep clay soil group arisen from the fine mass parent material, soil reaction is strong acid, good to moderate good drainage, low fertility. Ban chong (Bg),
Chiang Khong (Cg),
Choke Chai (Ci ),
Mae Taeng (Mt),
Nong Mot (Nm),
Pak Chong (Pc),
Sun Nern (Sn)
30
 Deep to very deep clay soil group found in mountainous area, soil reaction is strong acid, good drainage, moderate fertility. Chiang San (Ce),
Doi Pui (Dp)
31
 Deep to very deep clay soil group arisen from the fine mass parent material, found in mountainous area, soil reaction is neutral or base, good to moderate good drainage, moderate fertility. Loei (Lo),
Wang Hai (Wi)
33
 Very deep power sandy or very fine loam soil group arisen from the river sediment or alluvial fan , the soil reaction is a little acid to neutral, good to moderate drainage, moderate fertility. Don Yang En (Don),
Kamphaeng Phet (Kp),
Kamphaeng San (Ks),
Lam Sonthi (Ls),
Nam Duk (Nd),
Tat Panom (Tp),
Tapan Hin (Tph)
35
 Deep to very deep fine loam soil group arisen from distributaries sediment or coarse mass parent material, the soil reaction is a very strong acid, good to moderate drainage, low fertility. Don Rai (Dr),
Dan Sai (Ds),
Hang Chat (Hc),
Korat (Kt),
Satuk (Suk),
Warin (Wn),
Yasotorn (Yt)
36
 Deep to very deep fine loam soil group arisen from distributaries sediment or coarse mass parent material, the soil reaction is a very strong acid, good to moderate good drainage, low to moderate fertility. Petchabun (Pb),
Pran Buri (Pr),
Si Khiew (Si)
37
 Moderate deep coarse loam soil group arisen from material degradation or coarse alluvium to accumulate on top of the rockfall stratum at 50-100 cm. depth from the ground surface, the soil reaction is a very strong acid, good drainage, moderate to high fertility. Bo Thai (Bo),
Naku (Nu),
Tab Salao (Tas)
38
 Very deep coarse loam soil group arisen from riverbank sediment, the soil reaction is a little to moderate acid, good to moderate good drainage, moderate fertility. Chiang Mai (Cm),
Chumphol Buri (Chp),
Don Chaedee (Dc),
Sai Ngarm (Sg),
Ta Muang (Tm)
40
 Deep to very deep coarse loam soil group arisen from distributaries sediment or coarse parent material, the soil reaction is strong or moderate acid, good to moderate good drainage, low fertility. Chara Rat (Chr),
Chum Puang (Cpg),
Hup Krapong (Hg),
Huay Thalang (Ht),
San Patong (Sp),
Yang Talat (Yl )
41
 Moderate thick sand soil group arisen from distributaries sediment or coarse grain sediment on top of the clayish loam layer or clayish loam mixed with siltstone sand, the soil reaction is a little acid to neutral, good drainage on the soil layer of moderate good drainage, low fertility. Ban Phi (Bpi),
Kam Bong (Kg),
Maha Sarakham (Mk)
44
 Thick sand soil group arisen from distributaries sediment or coarse grain sediment, the soil reaction is a little acid to neutral, rather much drainage, low fertility. Chan Tuk (Cu),
Dan Khun Thot (Dk),
Nam Phong (Ng)
46
 Shallow soil group or very thick rock waste mixed with laterite; soil reaction is very strong acid, good drainage, low fertility. Chiang Khan (Ch),
Krabin Buri (Kb),
Pong Tong (Po),
Surin (Su)
47
 Shallow soil group to rock wall layer, soil reaction is acid to neutral, good drainage, low fertility. Li (Li), Muak Lek (Ml),
Sop Prap (So),
Nakhon Sawan (Ns),
Pong Namron (Pon),
Tali (Tl)
48
 Shallow soil group to rock fall or rock waste layer and may find rock wall layer within 150 cm. depth from the ground surface, soil reaction is acid to neutral, good drainage, low fertility. Mae Rim (Mr),
Nam Chun (Ncu),
Payao (Pao),
Tayang (Ty)
49
 Shallow soil group to laterite or band iron formation on top of clay layer, soil reaction is acid to neutral, good to moderate good drainage, low fertility. Borabu (Bb),
Phon Pisai (Pp),
Sakon (Sk),
Sa Kaew (Ska)
52
 Shallow soil group to marl or lime layer, soil reaction is base or alkaline, good drainage, moderate to high fertility. Bung Chanang (Bng),
Takhli (Tk)
54
 Moderate deep soil group to marl or lime layer, soil reaction is base or alkaline, good drainage, moderate fertility. Lam Phyaklang (Lg),
Lam Narai (Ln),
Samo Thod (Sat)
55
 Moderate deep soil group to rock wall, rock waste, rocks or laterite, soil reaction is neutral or base, good to moderate good drainage, moderate fertility. Chatturat (Ct)
Wang Saphung (Ws)
56
 Moderate deep soil group to rock wall, rock waste or laterite, soil reaction is strong acid neutral, good to moderate good drainage, low fertility. Lad Ya (Ly),
Pu Sana (Ps),
Phon Ngarm (Png)
60
 Loam soil group arisen from the complex alluvium, soil reaction is strong acid neutral, good to moderate good drainage, low fertility. AC-wd : Alluvial Complex,
well drained
61
 Loam soil group arisen from the hill-foot rocks arisen from their degradation or decadence, the rock wastes or rock fall accumulated at the foot of mountains can be dispersedly found, their characteristics and properties are not certain, good drainage, low fertility. Depend on Kind of gravels vary as geological formation)
Soil in the moisturized highland
26
 Deep to very deep clay soil group arisen from distributaries sediment or fine parent material, the soil reaction is very strong acid, good to moderate good drainage, low fertility. Ao Luk (Ak),
Huai Pong (Hp),
Krabi (Kbi),
Kok Kloi (Koi),
Lamphura (Ll),
Pakchan (Pac),
Pang-nga (Pga)
Phuket (Pk),
PaThew (Ptu),
Thai Muang (Tim)
27
 Very deep red clay soil group arisen from volcanic rock sediment, the soil reaction is strong acid, good drainage, moderate fertility. Nong Bon (Nb),
Ta Mai (Ti)
32
 Very deep loam or fine siltstone soil group arisen from riverbank sediment, the soil reaction is strong acid, good to moderate good drainage, moderate fertility. Lam Kaen (Lam),
Rue So (Ro),
Ta Khun (Tkn)
34
 Deep to very deep coarse loam soil group arisen from distributaries sediment or coarse mass source material, the soil reaction is strong acid, good to moderate good drainage, low fertility. Chalong (Chl),
Fang Daeng (Fd),
Kuan Kalong (Kkl),
Klong tom (Km),
Klong Nok Kratung (Knk),
Lahan(Lh),
Na Tam (Ntm),
Ta Sae (Te)
39
 Deep to very deep coarse loam soil group arisen from distributaries sediment or coarse mass parent material, the soil reaction is a little acid to base, rather much drainage, low fertility. Ko Hong (Kh),
Na Tawi (Nat),
Sa Dao (Sd),
Tung Wa (Tg)
42
 Sand soil group having compacted organic layer within 100 cm. depth from the ground surface, the soil reaction is a little acid to neutral, rather much drainage on soil layer having moderate good to bad drainage, low fertility. Ban Thon (Bh)
43
 Very deep sand soil group arisen from distributaries sediment or seaside sand ridge, the soil reaction is a little acid to base, rather much drainage, low fertility. Bacho (BC),
Hua Hin (Hh),
Lan Suan (Lan),
Mai Khao ( Mik),
Pattaya (Py),
Rayong (Ry),
Sattahip (Sh)
45
 Shallow soil group to laterite, rock waste or rock bed layer, soil reaction is strong acid, good to moderate good drainage, low fertility. Chomphon (Cp),
Hat Yai (Hy),
Chlong Chak (Kc),
Khao Khat (Kkt),
Nong Khla (Nok),
Tha Chang (Tac),
Yala (Ya)
50
 Moderate deep loam soil group to rock waste, rocks or foot wall, soil reaction is strong acid, good drainage, low fertility. Sawi (Sw),
Phato (Pto)
51
 Shallow soil group to foot wall, soil reaction is strong acid, good to rather much drainage, low fertility. Haui Yot (Ho),
Klong Teng (Klt),
Ranong (Rg),
Yi Ngor (Yg)
53
 Moderate deep clay soil group to foot wall, laterite or rock waste, soil reaction is strong acid, good drainage, low fertility. Na Thon (Ntn),
Olam Chiac (Oc),
Pa Dang Baesa (Pad),
Trad (Td),
Trang
High steep slope area
62
 Complex slope area having slope more than 35 percent, this vicinity area has not been studied, surveyed and classified because the area is high steep regarded as difficult for management and preservation for agricultural purpose. Slope complex