Zone II • Versions EN4
Abstract: This database is based on Guangdong Soil Type Chronicles, an outcome of the Second National Soil Survey published in 1996 by Science Press. The database included information on 212 soil types in Guangdong Province, covering such aspects as the distribution, area, main characters, land-use and production performance of the soil types. After standardization, an E-R data model was constructed which included the correlation between location and soil type, and the classification hierarchy according to the Genetic Soil Classification of China. The study resulted in a data product which recorded 700 soil horizons of 16 soil groups, 39 subgroups, 212 major soil types, 212 typical profiles and their physicochemical properties. The database can be widely used for land degradation assessments, environmental impact studies, soil carbon reserve studies, or as basic soil data to guide agricultural production.
Keywords: Guangdong soil; soil type database; Second National Soil Survey
|English title||A database of soil types in Guangdong: Based on the Second National Soil Survey|
|Data authors||Yin Chunmei, Shi Jianping, Pan Kai,Wei Wenxue|
|Datacorresponding author||Yin Chunmei (email@example.com)|
|Data collection due||1996|
|Geographical scope||104°29′E～112°04′′E, 20°54′N～26°23′N; specific areas include the whole Guangdong Province.|
|Data service system||<http://vdb3.soil.csdb.cn/front/detail-中南红壤区土壤综合数据库$zn_location_name?id=440000>;|
|Sources of funding||CAS informatization project – "Integration and application of basic scientific data in the field of Soil Science" (XXH12504-1-02); National Natural Science Foundation of China (41201260)|
|Database composition||This data set consists of nine subsets: soil groups in Guangdong, soil sub-groups in Guangdong, basic information of Guangdong soil types, landscape information of typical profiles, genetic horizon of typical profiles, physicochemical properties of typical soil profiles, statistical physicochemical properties of soil profiles, distributional relationship, and geographic information. The data volume is 0.62 MB.|
Soil type is the basic unit of soil classification. It is a cluster of soil pedons with similar profile morphology, development layer, physicochemical and biological characteristics, and production performances under similar water and heat conditions.1 The Second National Soil Survey (referred to as the "Second Survey" hereinafter), which began in 1979, consulted soil classifications at home and aborad. The survey is a milestone that marks the transition of soil classification in China from qualitative to quantitative, digitalized and data-oriented.2–3 It combined conventional views from soil genesis with characteristics of the diagnostic layer to divide soil types, through which a stable and unified soil classification scheme was established.
As a major achievement of the Second Survey, Guangdong Soil Type Chronicles was under compilation for nearly 4 years. During raw data collection, a detailed sampling plan was made and carried out according to national requirements and the specific situation of Guangdong Province.
More than 1800 samples of soil profiles were collected (including more than 700 collected at provincial level), and laboratory analyses of these samples (including trace element tests) generated nearly 15000 data items. The copy sent for review recorded 522 soil types spanning 131 soil families, 36 subgroups, 16 groups and 6 soil orders. However, for lack of diagnostic information, 212 soil types were finally included in Guangdong Soil Type Chronicles after validation, which spanned 16 soil groups and 39 subgroups. Among them, 99 types were paddy soils.4
This database was supported by the Chinese Academy of Sciences informatization project “Integration and application of basic scientific data in the field of Soil Science”. It is one of the achievements of the project “Integration of soil data resources in central & south China” accomplished according to the standards and specifications of scientific database and the data standards of soil science.
This database consists of eight subsets of data. After a series of standardization work, an E-R data model was constructed to correlate location and soil type. This data product recorded 212 soil types, 212 typical profiles and their physicochemical properties.
2.1 Classification of soil types
2.1.1 Principles of soil type division
Soil type is the foundation of soil classification. A soil type is a soil entity developed on the same parent material with a similar development degree and a relatively stable layer in the profile. It is a basic classification unit in the soil classification system. Soil types in Guangdong Province are divided according to the following principles:
(1) Homology: a soil type has the same parent material and character scalars, and its characteristic soil layer is of the same development degree.
(2) Similarity: a soil type has approximate hydrothermal conditions, approximate production performances and production potentials, similar profile configurations, and a sedimentary soil layer of approximate thickness.
(3) Relative stability: a soil type has relatively stable properties under normal tillage without serious interference.
2.1.2 Specific indicators of soil type division
In the Second Survey, soil types in Guangdong were divided based on soil thickness, soil structure, nutrient status, hydrothermal condition, terrain parent material, soil texture, acidosis damage and genetic horizon. For different soil types with similar profile configurations and morphological characteristics, the following indicators were adopted for soil classification:
(1) Thickness of organic matter: this was mainly used for the division of natural soil. The organic layer was categorized into thick (≥20 cm), medium (10~20 cm), and thin (≤10 cm).
(2) Thickness of soil layer: this was mainly used for the division of natural soil. There were thick soil layer (≥80 cm), medium soil layer (40 ~ 80cm), thin soil layer (≤40 cm).
According to the above two indicators, for example, red loam formed by the development of the granite parent material was divided into thick and thick (thick organic matter, thick soil layer) red loam, thick and thin red loam, and so on.
(3) Position of characteristic soil layer: take delta sedimentary soil field for example – it would be named as low oil field if the oil lattice (clay) layer appeared less than 30 cm deep below surface in relatively low and flat terrain; medium oil field if the layer was 30~50 cm deep in the middle sand field; and high oil field if the layer appeared over 50 cm deep in high-sand reclamation area.
(4) Heterogeneous soil layer: soil types could be divided according to the heterogeneous layer in the soil layer, such as shell layer, ginger layer, iron layer, iron plate and so on.
(5) Soil acidity and alkalinity: acidic, pH≤5.5; slightly acidic, pH 5.5 ~ 6.5; neutral, pH 6.5 ~ 7.5; slightly alkaline pH 7.5 ~ 8.5; alkaline, pH≥8.5.
(6) Development degree of characteristic soil layer: soil type was divided by embryologic features and its attribute indicators of the characteristic soil layer. For example, soil types could be categorized based on the development strength of the W layer for paddy soil and the development characteristics of the B layer for self-formed soil.
(7) Salinity and brackish acidity of paddy soil:
①The sediment soil field affected by seawater salinity was divided into light-salt field (salinity≤0.25%), medium-salt field (salinity=0.25%~0.5%), and heavy-salt field (salinity≥0.5%).
② According to soil sanity and acidity, littoral deposit field (which spreads at the exit of a shallow beach or river and has mangrove residue in subsoil layer) was classified into lightly salty acid field (sanity≤0.25％, pH≥5.5), moderately salty acid field (sanity=0.25％～0.5％, pH=4～5), and heavily salty acid field (sanity≥0.5％, pH≤4).
③ The sedimentary alluvial soil was distributed along shallow beaches or at the exit of salted fresh water and was buried in mangrove residues in the bottom soil. The soil was desalted during long-term tillage, with acid but no salt or slight seasonal salt. There were light acid reflux field (pH＝5～5.5), acid reflux field (pH＝4～5), and heavy acid reflux field (pH≤4).
(8) Soil texture: according to soil texture, a soil type was identified as sandy field, sandy-mud field, mud field, or clay field (for paddy soil), and (purple) sand, (red) sandy-mud field, (yellow) mud field, or (red) naughty-mud field (for dry land),, and so on.
2.2 Standardization of data contents
2.2.1 Standardization of soil classification
Soil classification in Guangdong abode by the Chinese Soil Classification System(Chinese National Soil Survey Office, 1998). Upper-level classification units adopted the continuous nomenclature of genetics, while lower-level units generally adopted mass naming, in which soil order, suborder and group were consistent with national standards of that time. Named according to diagnostic features of the soil-forming process, soil orders were categorized into anthrosol, ferralsol, primitive soil, semi-hydromorphic soil, hydromorphic soil, and saline-alkali soil. Nine suborders were named according to differentials of the soil-forming process. 16 soil types were named according to published records.
In this data set, we also added soil group names from the Soil Classification and Codes of National Standards (GB17296-2009)5 (referred to as GB2009 hereinafter) for comparison. Specific examples are shown in Table 1.
In Guangdong Soil Type Chronicles, soil subgroups were named in the format of characters indicating their soil-formation process plus group name. 36 subgroups were identified in total. We also added soil subgroup names and codes from both the Second Survey and GB2009 for comparison. Specific examples are shown in Table 2.
|Name of soilsubgroup as per this data set||Name of soilsubgroupas per the Second Survey (1980)||Name of soilsubgroup as per GB (GB17296-2009)|
|Lateritic red earth||Typical lateritic red earth||Typical lateritic red earth|
|Yellow latosolic red soil||Yellow latosolic red soil||Yellow latosolic red soil|
|Wet soil||Moist soil||Moist soil|
|Fixed sandy soil||Coastal aeolian sandy soil||Coastal aeolian sandy soil|
|Semi fixed sandy soil||Coastal aeolian sandy soil||Coastal aeolian sandy soil|
2.2.2 Nomenclature of soil types
Soil types in Guangdong basically adopted conventional names used by the masses, where cultivated land usually adopted uninominal nomenclature, and natural soil obeyed a simplified continuous naming method. Either way, they shared some common features of naming: paddy soils were denoted by the character “田[field]”. such as sandy field, terracotta field, and so on; “land[地]” was used to represent dry land, such as red sandy mud land, latosolic mud land, and so on. Zonal soil was generally named in the format of family name plus thickness of the organic matter and thickness of the soil layer, For example, the ma latosolic red soil family includes thick-medium ma latosolic red soil and slight-medium ma latosolic red soil. But soil types with singular feature tended to have the same name as their genus, like tidal sand cement soil and black calcareous soil.
2.2.3 Attribution of soil types
Soil types were attributed according to the principles stipulated by the national soil classification system, with some adjustments to certain soil types previously classified in the field census of Guangdong Province. For example, the thin layer soil of mountain area, which had no (B) layer, and whose underlying parent rock soil had been weathered or semi-weathered to form a rough matrix layer (AC soil), was categorized as coarse bone soil; soil with a surface layer below 10 cm, and with non-weathered parent rock or parent rock clastic (AD soil) bottom layer, was categorized as stone soil; and soil with a poorly-developed B layer (A (B) soil) was grouped into soil with corresponding property.
2.2.4 Coding of soil layer and soil texture
(1) Soil layer code
Paddy soil: plough horizon (Aa), plowpan (Ap), percogenic horizon (P), waterloggogenic horizon (W), dive layer (Gw), gley horizon (G), bleached horizon (E) and rot mud layer (M).
Dry cropland: top soil (A11), sub-top soil (A12), sub-soil layer (C1), C-horizon (C2).
Natural soil: litter organic layer (Ao), sod layer (As), organic layer (topsoil, A), parent material characteristic vanishing layer (deposition layer, B), parent material horizon (C-horizon, C), fragment of mother rock layer (D), hard rock layer (R). “(B)” indicates an undeveloped or poorly-developed deposit.
(2) Soil layer suffixes
The basic soil layer can be further divided into a series of specific layers according to the specific nature of its occurrence, indicated with one or two lowercase letters following major codes (Table 3).
|C||Accumulation of tuberculoses||mo||Iron manganese film|
|Ca(K)||Lime slab||k||Aggregation of calcium carbonate|
|Co||Coral fragment||Sb||Shell layer|
|e(E)||Rinsing characteristics||Na(Z)||Accumulation of sodium chloride|
|fe||Harmful iron||p||Disturbance caused by farming or other farming-related activities|
|g||Reflecting iron and manganese spots or patches caused by oxidation-reduction process||w||Changes of clay content, color, or structure of the soil layer that usually decorates B layer|
|h||Natural accumulation of organic matter in mineral soil||q||Accumulation of secondary silica|
|He||Mud carbon or mud carbon layer||u||Rust stripes caused by the rise and fall of the water table|
|t||Accumulation of clay||su||Aggregation of sulfides|
(3) Soil texture was classified and named in accordance with international standards. Some basic symbols include: sand (S), loam (L), clay (C) and silt (Si). Based on the above symbols, soil layers were named by comprehensively considering actual conditions. Specific texture symbols are detailed in Table 4.
2.2.5 Description of soil types
Soil profile configuration: each soil type has a specific profile configuration, and its characteristic soil layer reflects the properties of soil formation. For example, all waterloggogenic paddy soil types have an Aa-Ap-W-C configuration, and all rinsed paddy soil types have an Aa-Ap-E-C configuration, whose characteristic E layer shows that a lot of lateral seepage occurred during the soil-forming process. Alluvial soil, on the other hand, not only has an A-B-C profile configuration as general soil types do, but the mechanical composition of soil texture and the ratio of silt and clay indicate its texture type, such as alluvial sand, alluvial clay or mud. The nutrient contents of each soil type are also indicated, including total and available nitrogen, phosphorus and potassium, organic matter, trace elements and pH.
Typical profile reflects the central concept and character of a soil type. Description of a typical profile covers its sampling sites, habitat conditions, topographic sites, altitudes, parent material or parent-soil types, vegetation and land use, profile layers, soil structure and main physicochemical properties. Soil color was rectified by using the Munsell soil color charts, and soil texture was validated against international standards.
“Production performance” gathered information on the soil’s tillage suitability, fertility status, crop growth performance, existing problems, annual production, farming system, utilization and improvement measures, production practice and its outcomes, etc.
2.2.6 Methods for soil physicochemical analysis
For soil physicochemical analysis, we mainly referred to relevant technical regulations prescribed by the Outline of Provincial Summary of Soil Survey..7 We also consulted Methods for Soil Physical and Chemical Analysis8 compiled by the Institute of Soil Science, Chinese Academy of Sciences. Table 5 shows the analysis and test methods concerning each indicator.
|Indicator||Analysis method||Indicator||Analysis method|
|Water content||Oven drying method||Mechanical composition||Hydrometer method A|
|pH (H20)||Potentiometric method (soil: water = 1:2)||pH (KCl)||KCl extraction potential method (soil: solution = 1:2)|
|Bulk density||Cutting ring method||Soaking bulk density||Graduated cylinder, to soak and measure|
|Organic matter||Potassium dichromate & sulfuric acid oxidation method||Total P||Sodium hydroxide alkali fusion–molybdenum antimony colorimetric method|
|Ammonium nitrogen||Diffusion method–neutralization titration||Alkali hydrolysable nitrogen||Diffusion method–neutralization titration|
|Total N||H2SO4-K2SO4-CuSO4digestion –ordinary distillation||Available P||0.5M NaCO3 extraction (soil: solution = 1:2)–Mo-Sb colorimetric method|
|Total K||NaOH alkali fusion–flame photometry||Available K||Neutral ammonium acetate extraction – flame photometry|
|Slowly available potassium||1N HNO3 (soil: solution=1:10) extraction–flame photometric method||Fe2+||Phenanthroline chromogenic method–automatic flow injection analyzer|
|Total salt content||Solid residue method||Cation exchange capacity||NH4Ac extraction–flame photometry|
|Exchangeable acid in soil（H++Al3+）||Potassium chloride exchange–neutral titration||Total acidity of soil hydrolysate||Hydrolysis of CH3COONa–neutral titration|
|Exchangeable K & Na（Neutral and acid soil）||NH4Ac extraction – flame photometry||Exchangeable Ca & Mg (Neutral and acid soil)||NH4Ac extraction – flame photometry|
|Calcareous soil exchange||(NH4)2C2O4–NH4Cl method||Exchangeable Ca & Mg (Calcareous soil)||1N NaCl extraction–EDTA volumetric method|
|Firmness||Measured in field with soil hardness meter, made by Soil Chemistry Department, Zhejiang Agricultural University|
3.1 Database structure
Referring to the structure of soil databases at home and abroad,9–11 we built a soil type database with clear spatial distribution relations and classification hierarchies. Data can be queried and retrieved based on location and soil classification. Users are navigated through the “location-soil” correlation, that is, the logic order of “provinces -> cities/counties -> soil types -> soil information”, to reach detailed information of a target soil, including profile information, profile environment, physicochemical properties, etc.
This data set consists of nine subsets of data.
(1) Soil groups in Guangdong. It contains information on soil order, soil group, and soil group description. We added the soil group names and codes from GB (17296-2009) while retaining the group names from Guangdong Soil Type Chronicles.
(2) Soil subgroups in Guangdong. This sheet contains subgroup names and codes of the Second Survey and GB2009.
The above two sheets describe the relationship between soil genesis classification and soil type in Guangxi. There is a one-to-many relationship between soil groups and subgroups.
(3) Basic information of Guangdong soil types. This sheet includes information on soil group name, general description, parent material, profile configuration, main features, distribution and area, production performance, etc. This data sheet is mainly in text format.
(4) Landscape information of typical profiles. Each soil type has a typical soil profile. This sheet contains information on the collection sites, parent material, mean annual temperature, annual rainfall, accumulated temperature, frost-free periods, vegetation, land use, main features and other information of the typical soil profiles.
(5) Genetic horizon of typical profiles. It describes the occurrence horizon and its characteristics. Information includes the name, thickness, start and end depths, color, texture, structure, compactness and root condition of an occurrence horizon. There is a one-to-many relationship between soil types and soil horizons. A data field of “soil thickness” was added to the data set during data entry, and more detailed description was given to the thickness of the occurrence layer.
(6) Physicochemical properties of typical profiles. It contains information on soil nutrients, total nutrients, available nutrients, granulometric composition, texture, calcium carbonate, etc. One soil type has multiple occurrence layers, while each occurrence layer has different physicochemical properties. Legal units of measurement were added during the data set construction to complement the original data unit.
(7) Statistical physicochemical properties of soil profiles. It contains information of soil organic matter, total N/P/K, available nitrogen (N/P/K), particle composition, texture, pH and so on. One soil type has multiple occurrence layers, while each occurrence layer has different physicochemical properties. As original data were converted into legal units during data entry, this table included the legal units while retaining original data units and their values for provenance purposes.
(8) Distributional relationship. A soil type may be distributed among different counties/cities, while a county/city may have multiple soil types. This sheet was built to show the one-to-many relationship between soil types and their located places. It contains data fields like type ID, type name, county/city codes, county/city name, etc.
(9) Geographic information. This sheet was built for the convenience of location-based data queries. It contained the name, administrative code, latitude and longitude of the city/county where each soil type was distributed.
3.2 Data sample
This database only supports queries by location (city/county name). An example is given below to show the feature of this database.
Firstly, open the website to obtain the city/county names and their geographic information: <http://vdb3.soil.csdb.cn/front/detail-中南红壤区土壤综合数据库$zn_location_name?id=440000> (Figure 1).
Secondly, select Zhanjiang City, and basic information of all soil types in Zhanjiang will be displayed (Figure 2).
Thirdly, select “fixed sandy soil” (固定沙土), and we will be directed to its specific information, including its distribution, main characters, typical soil profile, landscape information, genetic horizon and physicochemical properties, etc. (Figure 3).
4.1 Data entry and quality assurance
Data input and correction were completed during 2014 – 2015 by the Institute of Subtropical Agricultural Ecology, Chinese Academy of Sciences. Data integrity and consistency were spot-checked and verified manually. During the data set construction, data fields, units and numerical values were reviewed by reference to source material. The unit of measurement was converted to legal units where appropriate. City/county names were amended and updated. A database design document was established. The dataset was submitted to the Institute of Soil Science, Chinese Academy of Sciences, Nanjing in 2015.
4.2 Concrete measures of quality assurance
4.2.1 Legal unit conversion
In the two original tables of physicochemical properties of typical soil profiles and statistical physicochemical properties of soil profiles, organic matter, total nitrogen, total phosphorus and total potassium were recorded in the unit of “%”. After data entry and revision, the original data field was retained, and a new data field was added to represent the legal measurement unit of “g/kg”. The soil particle composition was classified according to international standards, recorded in the unit of “%”; the soil bulk density unit was “g/cm3”; the unit for both cation exchange capacity and exchange cation was unified into “cmol/kg (+)”. So all the fields mentioned above have been converted to legal units of measurement.
4.2.2 Representation of sampling depth
In the raw data, the depth of a genetic horizon was represented by the start and end depths (e.g., 0cm~20 cm). During data entry, the data were decomposed to fit into two data fields, that is, the start and end depths of the genetic horizon, respectively. In order to better represent the relative and absolute thicknesses of the genetic horizon, layer thickness was added after the data were input and verified. For example, if the start and end depths of a genetic horizon are 10 cm and 34 cm respectively, the thickness of the soil layer should be 24 cm.
4.2.3 Standardization of soil classification
To standardize classification names is an important content of data integration in soil science. For a unified classification system, we recorded the names of soil groups and subgroups as per Guangdong Soil Type Chronicles, and added their corresponding names from GB/T 17296-2009 for comparison.
4.2.4 Update of administrative units
It took over 20 years from statistical survey to the publishing of Guangdong Soil Type Chronicles. This period witnessed great changes in the name and scope of various administrative divisions. In view of this, two data fields were added to record both the old and new county/city names. To facilitate data query, we also added the administrative division code (GB/T2260-2007)12 and their approximate latitude & longitude.
4.2.5 Data type conventions
Basic data types include texts, numbers, remarks, etc. Fields with data missing from the original source were marked by “null”.
Soil is the basis of agricultural development and the most important natural resource of a country. Soil type is the basic unit of soil classification that closely relates to agricultural production. Soil type information provides a scientific basis for soil utilization, soil formulation and fertilization, soil tillage and irrigation, and soil modification. It can also be used as basic data for allocation of agriculture, utilization and protection of soil resources, estimation of soil carbon/nitrogen reserves, as well as studies on soil nutrient dynamic changes and soil taxonomy. This study also aims to promote a full and efficient utilization of soil resource information. Guangdong Soil Type Chronicles provides the most authoritative, comprehensive and detailed information on the soil types of Guangdong Province.
Below are a list of notes on the usage of this data set:
(1) During the compilation of Guangdong Soil Type Chronicles, soil types with small areas and not enough statistics had been attributed to another soil type of the same family. This led to a smaller number of soil types recorded in this database, as compared with the actual number, as well as a greater area of certain soil types.
(2) Due to the editors' limited knowledge at the time when the book was compiled, certain soil types were not fully summarized. Repetitive and purely theoretical explanations were frequent in the discussion of certain soil types' production performance, especially regarding improvement and utilization measures, and the characteristics of various soil types were not fully reflected.
(3) In the later period of the Second Survey, soil texture analysis was mandated to use the international soil texture classification system. However, at city and county levels in Guangdong, sample analysis data followed the Kachinsky classification system at first. It was until then that the data were converted into the international system through a unified computer program.
While the database is stored in Science Data Bank (http://www.sciencedb.cn/dataSet/handle/460), it is simultaneously published at the website of Chinese Soil Database (http://vdb3.soil.csdb.cn/front/detail-中南红壤区土壤综合数据库$zn_location_name?id=440000). The platforms allow users to access the pages and make queries for detailed information without registration.
Thanks go to the members of the project “Integration and application of basic scientific data in the field of Soil Science”, particularly Professor Pan Xianzhang and Senior Engineer Gao Meirong.
Soil Science Society of China. The Classification of Soil Type and Genus in China. Nanjing: Jiangsu Science and Technology Press, 1989.
Chinese National Soil Survey Office. Chinese Soil Type Records. Beijing: China Agriculture Press, 1993.
China National Standardization Administration Committee. GB/T 17296-2009 Chinese Soil Classification and Codes. Beijing: Standards Press of China, 2009.
Institute of Soil Science, Chinese Academy of Sciences. Methods for Soil Physical and Chemical Analysis. Shanghai: Shanghai Science and Technology Press, 1978,
Shi X, Yu D, Warner E et al. Soil database of 1:1000000 digital soil survey and reference system of the Chinese Genetic Soil Classification System. Soil Survey Horizons 45 (2004): 129 – 136.
1. Yin C, Shi J, Pan K et al. A database of soil types in Guangdong: Based on the Second National Soil Survey. Science Data Bank. DOI: 10.11922/sciencedb.460
How to cite this article
Yin C, Shi J, Pan K et al. A database of soil types in Guangdong: Based on the Second National Soil Survey. China Scientific Data 3 (2018). DOI: 10.11922/csdata.170.2017.0147