HWSD metadata

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Map overview

Bulk data download is not available for this data source, in order to do that, please go to HWSD website

Full name:

Harmonized World Soil Database

Version:

2.0

Organization or Author:

FAO - Food and Agriculture Organization of the United Nations; IIASA - International Institute for Applied System Analysis

Abstract:

The Harmonized World Soil Database version 2.0 (HWSD v2.0) is a unique global soil inventory providing information on the morphological, chemical and physical properties of soils at approximately 1 km resolution. Its main objective is to be useful for modelers and to serve as a basis for prospective studies on agroecological zoning, food security and the impacts of climate change. HWSD v2.0 also serves an educational function, illustrating the geographical distribution of soils as well as their properties globally.

Service location:

HWSD

Geographical Coverage:

Global

GIS Data Type:

Vector - Polygon

Spatial resolution:

30 arc-second (1 km approximately)

Publication date:

2023-??-??

Reference period-start:

1995-??-??

Reference period-stop

2019-??-??

License:

CC BY-NC-SA 3.0 IGO

Key Soil Properties:

Coarse Fragments, sand, silt, Clay, USDA Texture, Bulk Density, Organic Carbon Content, pH, Nitrogen, C:N Ratio, Cation Exchange Capacity, Extractable Bases, Base Saturation, Aluminium, Sodium, Calcium Carbonate, Gypsum, Electrical Conductivity

Soil deph coverage (cm):

Up to 200 cm depth

Soil Functions:

Soil Threats:

Citation:

FAO & IIASA. 2023. Harmonized World Soil Database version 2.0. Rome and Laxenburg. https://doi.org/10.4060/cc3823en

Soil parameters overview

You can find more information regarding the statistical methodology in this link.

Original Soil Parameter	Unit of measurement	Description
AWC	mm	The maximum amount of water that the soil can hold that is available for plant growth. It is the difference between the amount of water in the soil at field capacity and the amount of water in the soil at wilting point. It is also referred to as Available Water Capacity (AWC). AWC depends on physical and chemical characteristics, but above all on effective depth or volume of the soil (FAO, 1995). The presence of a root-restricting layer reduces the water holding capacity, therefore the AWC is calculated until the rootable depth of a soil.
COARSE	%v	A coarse fragment is any primary soil particle with a nominal diametre greater than 2 mm. The data are directly available from the WISE30sec database.
SAND	%w	Sand comprises particles, or granules, ranging in diametre from 0.050 to 2 mm. An individual particle in this range size is termed a sand grain. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour). Sand is commonly divided into five sub-categories based on size: very fine sand (1/16–1/8 mm diametre), fine sand (1/8–1/4 mm), medium sand (1/4–1/2 mm), coarse sand (1/2–1 mm), and very coarse sand (1–2 mm). The data are directly available from the WISE30sec database.
SILT	%w	Silt is produced by the mechanical weathering of rock, as opposed to the chemical weathering that results in clays. This mechanical weathering can be due to grinding by glaciers, eolian abrasion (sandblasting by the wind) as well as water erosion of rocks on the beds of rivers and streams. Silt is sometimes known as “rock flour” or “stone dust”, especially when produced by glacial action. Mineralogically, silt is composed mainly of quartz and feldspar. Silt size is between 0.002 and 0.050 mm (USDA classification). The data are directly available from the WISE30sec database.
CLAY	%w	Clay is naturally occurring firm earthy material, composed primarily of fine-grained (diametre less than 0.002 mm) that is plastic when wet and hardens when heated and that consists primarily of hydrated silicates or aluminum. Clay is mostly composed of clay minerals which are phyllo-silicate minerals and minerals which impart plasticity and harden when fired or dried. The definition of "fine grained" used above is particles smaller than 2 μm, colloid chemists (and Eastern European soil scientists) may use 1 μm. In the database no difference is made between the two, but reported figures are used, whatever the source; these values are also used to determine the “USDA texture class” as given below. The data are directly available from the WISE30sec database.
TEXTURE_USDA	-	USDA texture class name and code. Soil texture is a soil property used to describe the relative proportion of different grain sizes of mineral particles in a soil. Particles are grouped according to their size into what are called soil separates (clay, silt, and sand). The soil texture class (e.g. sand, clay, loam, etc.) corresponds to a particular range of separate fractions, and is diagrammatically represented by the soil texture triangle.
BULK	g/cm3	Bulk density is defined as “the mass of the many particles of the material divided by the total volume they occupy”. Data are directly available in the WISE30sec database.
REF_BULK	g/cm3	Reference bulk density is a property of particulate materials. It is the mass of many particles of the material divided by the volume they occupy. The volume includes the space between the particles as well as the space in the pores of individual particles.
ORG_CARBON	%w	Organic Carbon is together with pH, the best simple indicator of the health status of the soil. Moderate to high amounts of organic carbon are associated with fertile soils with a good structure. Data are directly derived from WISE30sec.
PH_WATER	-	This field gives the soil reaction. The pH, measured in a soil-water solution, is a measure for the acidity and alkalinity of the soil. Data are directly derived from WISE30sec.
TOTAL_N	g/kg	Soil total nitrogen is a major determinant and indicator of soil fertility and quality in an agricultural ecosystem. Data are directly derived from WISE30sec
CN_RATIO	-	A carbon-to-nitrogen ratio is a ratio of the mass of carbon to the mass of nitrogen in soil material. The C:N ratio is a key indicator as it describes a balance between energetic foods (represented by carbon) and material to build protein with (represented by nitrogen). An optimal C:N ratio of around 24:1 provides for higher microbial activity (USDA, 2011). Data are directly derived from WISE30sec. Note that C/N ratios have been calculated as is from the measured data (CNrt), not as the ratio of the derived values for C and N, ditto for CECclay, as this would introduce additional errors.
CEC_SOIL	cmolc/kg	of the fine earth fraction (cmolc/kg). The total nutrient fixing capacity of a soil is well expressed by its Cation Exchange Capacity. Soils with low CEC have little resilience and cannot build up stores of nutrients. Many sandy soils have CEC less than 4 cmolc/kg. The clay content, the clay type and the organic matter content all determine the total nutrient storage capacity. Values more than 10 cmolc/kg are considered satisfactory for most crops. Data are derived directly from the WISE30sec database.
CEC_CLAY	cmolc/kg	corrected for contribution of organic matter (cmolc/kg). This field gives the cation exchange capacity of the clay fraction corrected for the organic matter content in the layer concerned. The type of clay mineral dominantly present in the soil often characterizes a specific set of pedogenetic factors in which the soil has developed. Tropical, leaching climates produce the clay mineral kaolinite, while confined conditions rich in Ca and Mg in climates with a pronounced dry season encourage the formation of the clay mineral smectite (montmorillonite). CECclay is calculated from CECsoil by assuming a mean contribution of 350 cmolc/kg OC, the common range being from 150 to over 750 cmolc/kg (Klamt and Sombroek, 1988). Data are directly derived from the WISE30sec database.
CEC_EFF	cmolc/kg	ECEC is defined as the sum of exchangeable (Ca++, Mg++, K+, Na+) plus the sum of exchangeable (H+, Al+++) (Van Reeuwijk, 2002). Data are derived directly from the WISE30sec database.
TEB	cmolc/kg	Total exchangeable bases stand for the sum of exchangeable cations in a soil: sodium (Na+), calcium (Ca++), magnesium (Mg++) and Potassium (K+). Data are directly derived from the WISE30sec database.
BSAT	%	The base saturation measures the sum of exchangeable cations (nutrients) Na+, Ca++, Mg++ and K+ as a percentage of the overall exchange capacity of the soil (including the same cations plus H+ and Al+++). The value often shows a near linear correlation with pH. Data are derived directly from the WISE30sec database. ( % of CECsoil)
ALUM_SAT	%	The exchangeable aluminum percentage (ALSA) has been set at zero when pHwater is higher than 5.5. Data are derived directly from the WISE30sec database. (% of ECEC)
ESP	%	The exchangeable sodium percentage has been used to indicate levels of sodium in soils. It is calculated as the ratio of Na in the CEC (or sum of cations) ESP= Na*100/CECsoil. Data are derived directly from the WISE30sec database.
TCARBON_EQ	%w	calcium carbonate is a chemical compound (a salt), with the chemical formula CaCO3. It is a common substance found as rock in all parts of the world. Calcium carbonate is quite common in soils particularly in drier areas and it may occur in different forms as mycelium-like threads, as soft powdery lime, as harder concretions or cemented in petrocalcic horizons. Low levels of calcium carbonate enhance soil structure and are generally beneficial for crop production but at higher concentrations they may induce iron deficiency and when cemented limit the water storage capacity of soils. Data are derived directly from the WISE30sec database.
GYPSUM	%w	Gypsum is a chemical compound (a salt) which occurs occasionally in soils particularly in the driest areas of the globe where it can occur in a flower-like form typically opaque with embedded sand grains called desert rose. In soils it may occur in fibers, crystals or soft. Data are derived directly from the WISE30sec database.
ELEC_COND	dS/m	Coastal and desert soils can be enriched with water-soluble salts or salts more soluble than gypsum. The salt content of a soil can be roughly estimated from the Electrical Conductivity of the soil measured in a saturated soil paste or a more diluted suspension of soil in water. Data are directly derived from the WISE30sec database.