Field Description UNITS DSMW SOTWIS CHINA ESDB
S_GRAVEL Subsoil Gravel Content %vol. √ √ √ √
S_SAND Subsoil Sand Fraction % wt. √ √ √ √
S_SILT Subsoil Silt Fraction % wt. √ √ √ √
S_CLAY Subsoil Clay Fraction % wt. √ √ √ √
S_USDA_TEX_CLASS
Subsoil USDA Texture
Classification
name √ √ √ √
S_REF_BULK_DENSITY
Subsoil Reference Bulk
Density
kg/dm3 √ √ √ √
S_OC Subsoil Organic Carbon % weight √ √ √ √
S_PH_H2O Subsoil pH (H2O) -log(H
+
) √ √ √ √
S_CEC_CLAY Subsoil CEC (clay) cmol/kg √ √ √ √
S_CEC_SOIL Subsoil CEC (soil) cmol/kg √ √ √ √
S_BS Subsoil Base Saturation % √ √ √ √
S_TEB Subsoil TEB cmol/kg √ √ √ √
S_CACO3 Subsoil Calcium Carbonate % weight √ √ √ √
S_CASO4 Subsoil Gypsum % weight √ √ √ √
S_ESP Subsoil Sodicity (ESP) % √ √ √ √
Physico-chemical properties
Sub Soil information
S_ECE Subsoil Salinity (ECe) dS/m √ √ √ √
2.3 Field descriptions
This section explains the content of the fields in the database. It describes the procedures used to
correlate the various source data in order to obtain the harmonized database.
The DSMW, China and ESDB mapping unit information has been linked to respectively topsoil and
subsoil parameters derived from the World Inventory of Soil Emissions (WISE) soil profile database
(Batjes et al., 1997 and Batjes, 2002). The linkage was established through either the FAO-74
(DSMW) or the FAO-90 (China and ESDB) soil unit symbol by three topsoil texture classes (i.e.,
coarse, medium and fine) as provided in the mapping unit information in each of the three original
databases. The SOTER-derived part of the database, referred to here as SOTWIS databases includes,
soil parameter estimates for five standard depths (0–20 cm, 20–40cm, 40–60 cm, 60–80 cm and 80–
100cm) and five soil textural classes (coarse, medium, medium fine, fine and very fine (see Finke et
al. pg. 79 CEC, (1985)) (Batjes 2003, Van Engelen et al, 2005); these values were later converted to
standard depths of 0–30 cm and 30–100 cm at IIASA
2
The WISE database has been used to prepare two separate sets of parameter estimates, i.e. based on
the FAO-74 and FAO-90 soil classification respectively. For a large part of the ESBD map, soil unit
correlations with FAO-90 were available. Where correlations with FAO-90 were missing or not
available, FAO and IIASA staff, on the basis of soil characteristics and other available classifications
(FAO-85 and WRB) have completed correlations with FAO-90
3
. For the soil map of China (1:1
million) systematic soil correlations with both FAO-74 and FAO-90 classifications were unavailable.
2
In the applications for the FAO/IIASA AEZ model, the original five depth classes (0–20cm, 20–40 cm, 40–60
cm, 60–80 cm and 80–100 cm) and five textural classes in SOTWIS (Batjes, 2003) have been simplified to two
depth classes (0–30cm and 30–100cm) and three textural classes by calculating depth-weighted averages. This
simplification was required to enable the harmonization with the less precise information contained in the other
databases used.
In soil evaluation for agricultural purposes at country, regional or global scales as applied in the FAO/IIASA
AEZ model, preference is given to the two depth classes system as was used for WISE (Batjes et al, 1997 and
Batjes, 2002). For other applications the use of more precise depth and textural classes as provided in SOTWIS
are considered preferable.
3
The correlations of the FAO-85 classification with FAO-90 are subject to review by JRC; updates to be
considered for a next version of HWSD.
Harmonized World Soil Database (version 1.1)
5