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A database of soil types in Guangxi: Based on the Second National Soil Survey
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Abstract & Keywords
Abstract: This database is based on Soil Types in Guangxi, an outcome of the Second National Soil Survey published by Guangxi Science and Technology Press in 1990. It compiles information on the distribution, area, main characters, typical profiles, performance, and physicochemical properties of major soil types in Guangxi. After a series of standardization work, an entity-relationship (E-R) data model is constructed to demonstrate the location-soil type relation, as well as the classification relation according to Soil Genesis and Classification of China. It results in a database which contains 15 soil groups, 28 subgroups, 276 main soil types, 269 typical profiles, 930 soil horizons and theirs physicochemical properties. The database can be widely used for land degradation assessments, environmental impact studies, soil carbon reserve studies, or as a soil database to guide agricultural production.
Keywords: Guangxi soil; soil type database; Second National Soil Survey
Database Profile
Chinese title广西土种志——基于全国第二次土壤普查数据集
English titleA database of soil types in Guangxi: Based on the Second National Soil Survey
Corresponding authorYin Chunmei (cmyin@isa.ac.cn)
Data authorYin Chunmei
Time range1990
Geographical scopeGuangxi (104°29' – 112°04'N, 20°54' – 26°23'E)
Data format*.xlsData volume0.55 MB
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=450000>;
<http://www.sciencedb.cn/dataSet/handle/385>
Sources of fundingCAS 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 compositionThis database consists of eight subsets: soil groups in Guangxi, soil sub-groups in Guangxi, basic information of Guangxi soil types, landscape information of typical profiles, genetic horizon of typical profiles, physicochemical properties of typical profiles, distributional relationship, and geographic information. The data volume is 0.55 MB.
1.   Introduction
Soil type is the basic unit of soil classification and large-scale soil survey mapping. It provides the basis for assessing and managing agricultural production.1 The Second National Soil Survey (referred to as the "Second Survey" hereinafter), which began in 1979, drew from both domestic and foreign soil classifications. It is a milestone that marks the transition of soil classification in China from qualitative to quantitative, informatization- and data-oriented.2–3 It not only preserved conventional viewpoints from soil genesis, but also introduced diagnostic characteristics of the diagnostic layer to divide soil types, through which a stable and unified soil classification scheme was established. In the Second Survey of Guangxi, 186 973 soil profiles were observed, 15 112 soil profile samples (39 369 layers) were analyzed, 53 339 samples were tested for their physical and chemical indexes, 1 043 381 samples was tested for their available indexes, and a total of 480 000 000 data records were obtained. Finally, 326 soil types were identified across the whole region, 276 of which were included and described by Soil Types in Guangxi published in 1993.
This database was supported by the Chinese Academy of Sciences informatization program "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 databases and the data standards of soil sciences.
This database consists of eight subsets of data. After a series of standardization work, an E-R data model is constructed to correlate location and soil type. This data product records 276 soil types, 269 typical profiles and their physicochemical properties.
2.   Data collection and processing
2.1   Classification of soil types in Guangxi
Within the same geographical landscape, soil parent material and soil solum structure, soil types are mainly classified based on soil texture, thickness, pH value, iron content, gravel content, barrier layer depth, and so on. The indicators of soil classification are as follows:
(1) Soil thickness
Non-tillage soil is divided into thin layer (< 40 cm), medium layer (40 – 80 cm) and thick layer (> 80 cm) according to soil thickness. Within this standard, for example, there are lateritic red soils of thin layer, medium layer and thick layer.
(2) Characteristic soil layer
According to the position of the characteristic soil layer, soil is divided into shallow, medium and deep types. For example, gleyed paddy soil is divided into shallow gleyed soils (type A-G), medium gleyed soils (type A-P-G), and deep gleyed soils (type A-P-C-G); iron bottom soil is divided into shallow iron bottom fields (iron layer located less than 30 cm deep), deep iron bottom fields (iron layer located more than 30 cm deep).
(3) Barrier (heterogeneous) soil layer
Soil types are classified according to different barrier types, such as iron sublayer, iron disk layer, black mud layer, incubation layer or daub layer. According to this classification standard, there are iron sub soils, black clay soils, white mud soils, etc.
(4) Gravel quality
When the content of gravel soil (>2 mm) is counted, there are heavy stone soils (gravel content > 30%) and light stone soils (gravel content ≤ 30%).
(5) Soil texture
When the physical clay (< 0.01 mm) in the surface soil layer (or tillage layer) is counted, there are sandy soils (< 30%), loamy soils (or sand mud) (30% – 60%), and clay soils (> 60%).
(6) Soil pH
According to soil pH, there are acidic soils (pH < 6.5), neutral soils (6.5 ≤ pH ≤ 7.5), and calcareous soils (pH > 7.5, with lime reaction).
(7) Characteristic soil development
This is to classify soil based on its overall development level, including morphological characters, physicochemical properties and production performance. For instance, according to the level of soil fertility and maturity, there are mud meat fields, mud bone fields, oil sandy fields and so on.
(8) Salinity
According to the proportion of chloride salts, there are high saline soils (salinity > 0.1%) and low saline soils (salinity ≤ 0.1%).
2.2   Data contents standardization
2.2.1   Standardization of soil classification
Soil groups in Guangxi are classified according to Soil Genesis and Classification of China (1980), a summary specification resulted from the Second Survey4. On the basis of that, our study adds 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.
Table 1   Classification of soil groups in Guangxi
Name of soilgroup as per this databaseName of soilgroup as per the Second Survey (1980)Name of soil group as per GB (GB17296-2009)
Lateritic red earthsLateritic red earthsLateritic red earths
Yellow-brown earthsYellow-brown earthsYellow-brown earths
Red clay soilsRed clay soilsRed clay soils
Coastal solonchaksCoastal solonchaksCoastal solonchaks
Soil sub-groups in Soil Types in Guangxi are named slightly different from the Second Survey. Our study adds the Soil Classification and Codes of both the Second Survey and GB2009 for comparison. Specific examples are shown in Table 2.
Table 2   Classification of soil sub-groups in Guangxi
Name of soilsub-group as per this databaseName of soilsub-group as per the Second Survey (1980)Name of soilsub-group as per GB (GB17296-2009)
Lateritic red earthsTypical lateritic red earthsTypical lateritic red earths
Red earthsTypical red earthsTypical red earths
Yellow red earthsYellow red earthsYellow red earths
Weakly developed red earthsWeakly developed red earthsWeakly developed red earths
LatosolsLatosolsTypical Latosols
2.2.2   Attribution of soil types
Soil types in Guangxi are attributed according to the classification system of the Second Survey. First sorted by soil groups, soil types are then sequenced and coded. Attribution of soil types also shows information on the geographical location, topographic condition, distributed administrative region and area of respective soil types.
2.2.3   Nomenclature of soil types
The nomenclature of soil types in Guangxi observes soil properties and customary references of the masses, with classification indicators added as modifiers, such as crispy rice fields, muddy meat fields, iron soils, etc. Systematically, "土[soil]" is used to designate non-tillage soils while tillage soils are denoted by "泥土[earth]". Non zonal soils generally follow customary nomenclature, such as purple soil, black lime soil, fluvo aquic soil, etc. Paddy soils are marked by the character "田[field]". In addition, the nomenclature is assisted by soil classification indicators. For example, soil of different textures was distinguished by adding a prefix "沙[sandy]", "壤[loamy]", or "粘[clay]". Soil of different pH values is distinguished by adding the characters "酸性[acidic]", or "石灰性[alkaline]".
2.2.4   Soil layer coding
Soil layer is coded according to its genetic horizon (Table 3). The genetic layer can be further divided into several sublayers represented by a capital letter according to its developmental levels, followed by an Arabia numeral as its suffix. For example, the O layer could be divided into O1, O2, O3; the B layer could be divided into B1, B2, B3, etc. When a soil layer combines the properties of two major genetic layers (also known as a transition layer), such as AB, AE, BE, BA, the first letter represents the dominant soil layer.
Table 3   Soil layers and their corresponding codes
Soil layerCodeSoil layerCode
Surface or tillage horizonAAlbic horizonE
Subsoil horizon (a mineral layer whose parent material disappears)BPeat horizonM
Plow panPC-horizon (the parent material layer less affected by soil formation)C
Water logogenic horizonWHard rock layerR
Gley horizonGOrganic soil material layerO
The soil genetic layer can be further divided into a series of sublayers according to the specific nature of soil genesis, represented by one or two lowercase letters as the suffix (Table 4).
Table 4   Codes of soil sublayers
CodeMeaningCodeMeaning
aHighly decomposed organic matternAccumulation of exchangeable sodium
bMineral soil layer buried in mineral soilpDisturbance caused by tillage or other farming activities
cCentral nodules or rigid agglomerated nodules, which mainly refers to iron, aluminum, and manganese nodules, excluding those formed by silica, lime or more soluble saltqAccumulation of secondary siliceous matter
dBleached layerrSemi weathered layer with soft substrate that can be dug with shovels but whose roots cannot be penetrated, such as Cr
eSemi decomposed organic mattersAggregates of iron manganese, such as stripes, gum membranes and nodules, such as Bs
fPermanently frozen layer with ice crystal, exclusive of the dry-frozen layertClay illuviation
gIron manganese spots and plaques caused by redox processesvReticulate, red and white, rich in iron, hard while moist, extra hard while dry
hThe layer where organic matter is naturally accumulated in mineral soilwLocal weathering results in secondary clay formation and free oxide release; with granular, blocky, or prismatic structure; generally as a modifier of B layers
iLess decomposed organic matterxOf crisp disk features, high bulk density, brittleness
kAggregation of calcium carbonateyAccumulation of gypsum
mStrong cementation, solidification, and hardeningzSoluble salt accumulation, such as Az
2.2.5   Description of soil types
"Main character overview" mainly describes the magnitude index and range of soil type classification. "Statistical information of profiles" records the physicochemical characteristics of typical profiles in different regions, wherein the average and variation coefficients are calculated to represent the central and marginal concepts of each soil types.
"Typical soil profile" delineates the central concept of the soil classification indicators, and other characters should be within the range of variation. It also records sampling location, geographical landscape and parent material. It contains standardized description of soil layers and complete physicochemical analysis results. Measurement and description of soil color abides by Munsell Soil Color Charts. Two systems of nomenclature are used here, national standard and Kachinsky, as a result of different methods used to analyze soil texture during different time periods.
"Production performance" gathers information on soil suitability for growing local, speciality and high-quality products, as well as on human experience in soil fertility improvement, based on which suggestions are put forward for soil exploitation and improvement.
2.2.6   Methods for soil physicochemical analysis
For soil physicochemical analysis, the study mainly refers to Soil Survey Technique6 and the chapter "Items and Methods for Analysis" in Provincial Summary Outline for Soil Survey.7 It also consults 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 for each indicator.
Table 5   Methods for soil physical and chemical analysis
IndicatorAnalysis methodIndicatorAnalysis method
Water contentOven drying methodMechanical compositionHydrometer method A
pH (H20)Potentiometric method (soil: water = 1:2)pH (KCl)KCl extraction potential method (soil: solution = 1:2)
Organic matterPotassium dichromate & sulfuric acid oxidation methodTotal PSodium hydroxide alkali fusion – molybdenum antimony colorimetric method
Total NH2SO4-K2SO4-CuSO4 digestion – ordinary distillationAvailable P0.5M NaCO3 extraction (soil: solution = 1:20) – Mo-Sb colorimetric method
Total KNaOH alkali fusion – flame photometryAvailable KNeutral ammonium acetate extraction – flame photometry
Cation exchange capacityExchangeable K & NaNH4Ac extraction – flame photometryNeutral and acidic exchange capacityAmmonium acetate method
Exchangeable CaNH4Ac extraction – EDTA volumetric methodCalcareous soil exchange capacityAmmonium oxalate – ammonium chloride method
Exchangeable MgNH4Ac extraction – subtraction methodExchangeable Ca & MgNaCl extraction – EDTA volumetric method (deduct soluble ACO3- , CO32- )
3.   Data description
3.1   Database structure
Referring to the structure of soil resource 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 according to location and soil classification. Users are navigated by the "location-soil" correlation, through the logic relationship of "provinces -> cities (country) name -> soil types -> soil information", to reach detailed information of any target soil, including profile information, profile environment, physicochemical properties, etc.
This database consists of the following eight subsets.
(1) Soil groups in Guangxi. It contains information on soil order, soil group, and soil group description. It adds the soil group names and codes as per GB (17296-2009) while retaining the soil group names as per Soil Types in Guangxi.
(2) Soil subgroups in Guangxi. 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 Guangxi soil types. This sheet includes information on soil group name, general description, parent material, profile configuration, main features, distribution and area, production performance, etc., which are raw data directly copied from original references.
(4) Landscape information of typical profiles. Each soil type has a typical soil profile. This sheet contains information on the collection sites, latitude and longitude, topography, elevation, parent material, natural vegetation and land-use information of typical profiles. Latitude and longitude are new information added during the database construction.
(5) Genetic horizon of typical profiles. It describes the occurrence horizon and its characteristics. There is a one-to-many relationship between soil types and soil horizons. Soil thickness was added as new information during the database construction.
(6) Physicochemical properties of typical profiles. It contains information on soil nutrients, total nutrients, available nutrients, grain composition, texture, calcium carbonate, etc. Legal unit of measurement was added during the database construction to complement the original data unit.
(7) 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, country/city codes, county/city name, etc.
(8) Geographic information. This sheet was built for the convenience of geographic unit (county/city)-based data queries. It contains the name, latitude and longitude of the city/county where each soil type is distributed.
3.2   Data sample
This database only supports queries by location (city/country name). An example is given below to show the characteristics of the database.
(1) 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=450000 (Figure 1).
(2) Select Qinzhou City, and the basic information of all soil types in Qinzhou will show up (Figure 2).
(3) Select oil sandy field, and we will be directed to its detailed information, including its distribution, main characters, typical soil profile, landscape information, genetic horizon and physicochemical properties, etc. (Figure 3).


Figure 1   Counties and cities of Guangxi and their geographic information


Figure 2   Part of the soil types distributed in Qinzhou, Guangxi


Figure 3   Detailed information of oil sand field in Qinzhou, Guangxi
4.   Quality control and assessment
4.1   Data entry and quality assurance
Data input and correction was completed during 2014 – 2015 by the Institute of Subtropical Agricultural Ecology, Chinese Academy of Sciences. Data integrity and consistency was spot-checked and manually verified. During the database construction, data fields, units and numerical values were reviewed by reference to source material. 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 original physicochemical property table, 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 was in the unit of "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
The depth of genetic horizon in raw data is represented by relative thickness (e.g., 20 cm), whereby absolute depth is hard to be distinguished from depth range. In view of this, two data fields were calculated and entered by referring to ISO 28258, which were the highest and lowest layer depths respectively (for example, 0, 20).
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, the names of soil groups and subgroups in this database were recorded as per Soil Types in Guangxi, the Second Survey and GB2009 respectively.
4.2.4   Update of administrative units
Great changes have taken place in the name and boundary of administrative units since the 1980s.Where appropriate, data fields were added to record both the old and new county/city names. For the convenience of data query, the administrative division code (GB/T2260-2007)12 and approximate latitude & longitude of corresponding provinces, cities and countries were also added.
4.2.5   Data type conventions
Basic data types include texts, numbers, remarks, etc. Data that are missing in the original source are represented by "null".
Acknowledgments
Thanks go to 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.
1.
Guangxi Soil and Fertilizer Station. Guangxi Soil Type Records. Nanning: Guangxi Science and Technology Press, 1990.
2.
Soil Science Society of China. The Classification of Soil Type and Genus in China. Nanjing: Jiangsu Science and Technology Press, 1989.
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Chinese National Soil Survey Office. Chinese Soil Type Records. Beijing: China Agriculture Press, 1993.
4.
Chinese National Soil Survey Office. Chinese Soils. Beijing: China Agriculture Press, 1998.
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China National Standardization Administration Committee. GB/T 17296-2009 Chinese Soil Classification and Codes. Beijing: Standards Press of China, 2009.
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Guangxi Agricultural Bureau. Soil Survey Technique. Nanning: Guangxi People's Press, 1980.
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Chinese Soil Survey Office. Outline of provincial summary of soil survey, 1979.
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Institute of Soil Science, Chinese Academy of Sciences. Methods for Soil Physical and Chemical Analysis. Shanghai: Shanghai Science and Technology Press, 1978.
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Shi X, Yu D, Warner E et al. Soil Database of 1:1 000 000 Digital Soil Survey and Reference System of the Chinese Genetic Soil Classification System. Soil Survey Horizons 45 (2004): 129 – 136.
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FAO, IIASA, ISRIC et al. Harmonized World Soil Database (version 1.2). Rome, Italy, 2012.
11.
ISO 28258:2013 Soil quality – Digital exchange of soil-related data. 2013.
12.
China National Standardization Administration Committee. GB/T2260-2007 Code of Administrative Divisions of the People’s Republic of China. Beijing: Standards Press of China, 2007.
Data citation
1. Yin C, Shi J, Pan Kai et al. A database of soil types in Guangxi: Based on the Second National Soil Survey. Science Data Bank. DOI: 10.11922/sciencedb.385
Article and author information
How to cite this article
Yin C, Shi J, Pan Kai et al. A database of soil types in Guangxi: Based on the Second National Soil Survey. China Scientific Data 2 (2017). DOI: 10.11922/csdata.170.2017.0133
Yin Chunmei
data entry, data reconciliation and quality control.
cmyin@isa.ac.cn
MSc, Senior Engineer; research area: agricultural ecosystem monitoring.
Shi Jianping
database design, standard and specification development, and quality control.
Senior Engineer; research area: soil information management.
Wei Wenxue
database development and maintenance.
MSc, Engineer; research area: soil information system.
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)
Publication records
Published: Sept. 5, 2017 ( VersionsEN2
Released: April 19, 2017 ( VersionsZH1
Published: Sept. 5, 2017 ( VersionsZH2
Updated: Sept. 5, 2017 ( VersionsZH3
References
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