The Soil Geographical Database of Europe
This database forms the core of European Soil Information System (EUSIS) developed by the action 'Monitoring the State of European Soils' (MOSES) of the Land Management and Natural Hazards Unit (LMNH) of the Institute for Environment and Sustainability (IES) of the JRC. Its history dates back to the mid 80's:
In 1985, the Commission of the European Communities published a soil map of the EC at 1:1,000,000 scale (CEC, 1985). In 1986, this map was digitised to build a soil database to be included in the CORINE project (Co-ordination of Information on the Environment). This database was called the Soil Geographical Database of the EC, version 1. The database was enriched in 1990-1991 from the archive documents of the original EC Soil Map and became version 2. The JRC then formed the Soil and GIS Support Group with experts to give some advice concerning this database. These experts recommended that new information should be added and each participating country should make updates, leading to the current version 4.0 of the database.
The aim of the Soil Geographical Database at scale 1:1,000,000 is to provide a harmonised set of soil parameters covering Europe and the Mediterranean countries to be used in agro-meteorological and environmental modelling at regional, state, or continental levels. Its elaboration focuses on these objectives.
Originally covering countries of the European Union, the database has recently been extended to Central European and Scandinavian countries. It currently covers Albania, Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, FYROM (Former Yugoslav Republic of Macedonia), Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Netherlands, Norway, Poland, Portugal, Romania, Serbia and Montenegro, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. The extension is completed for Iceland and the New Independent States (NIS) covering Belarus, Moldova, Russia and Ukraine. Finally, work is on-going to further extend it to other Mediterranean countries: Algeria, Cyprus, Egypt, Jordan, Lebanon, Malta, Morocco, Palestine, Syria, Tunisia and Turkey.
Beside these geographical extensions, the database has also experienced important changes during its lifetime. The latest major changes concern the introduction of a new extended list for parent materials, and, for coding soil types, the use of the new World Reference Base (WRB) for Soil Resources in association with the 1990 FAO-UNESCO revised legend.
The database contains a list of SOIL_STU, characterizing distinct soil types that have been identified and described. The STU's are described by attributes (variables) specifying the nature and properties of the soils, for example the texture, the moisture regime, the stoniness, etc. The scale selected for the geographical representation is the 1:1,000,000. At that scale, it is not technically feasible to delineate each STU. Therefore STU's are grouped into 's stored in table SOIL_SMU to form soil associations. The criteria for soil groupings and SMU delineation have taken into account the functioning of pedological systems within the landscape. Although the location of each STU within a SMU is unknown, the relative amount within a SMU is known and stored in table LINK_SMU_STU. The sum of STU's within each SMU adds up to 100%. A detailed instruction guide and full documentation can be found in document EUR_20422_EN.pdf.'s stored in table
Soil data used in the BIOMA platform
The soil data of version 4.0 of the Soil Geographical Database of Europe (SGDBE) is used in the BIOMA platform to determine soil input variables to the agrometeorological model giving information about the soil type’s geographical location and the soil properties which are needed to simulate the crop growth during the year. The main soil properties are soil depth aiming at defining the potential rooting depth, and water retention properties giving through soil physical groups.The description of the soil characteristics for the crop simulation model in CGMS only relies on these two parameters. They fully describe the soil for simulation purposes.
Each STU is attributed to a rooting depth class (by CALCULATED_ROOTING_DEPTH in table ROOTING_DEPTH) and a soil physical group (by SOIL_GROUP_NO in table SOIL_PHYSICAL_GROUP) defining the available water capacity (AWC).
The AWC is a static soil characteristic and gives the amount of water between field capacity (wet soil) and wilting point (no water available for plants anymore) per unit length rooting depth. Multiplication of AWC and rooting depth gives the maximum available water which a soil can supply to a plant. It should be noted that the rain fed crop yields of the CGMS are more sensitive to the rooting depth than to the soil physical group (van der Goot, 1998b).
|Determining rooting depth class per soil typologic unit|
|The rooting depth is derived from soil attributes like soil name, depth at which obstacle to roots occur depth at which texture changes etc. using pedo transfer rules. More information on these rules can be found in the documentation of the SINFO study. The definition of the rooting depth classes for the CGMS is as follows.
|Determining available water capacity per soil physical group|
| In CGMS the soil physical group is defined by the volumetric soil moisture content at wilting point (pF 4.2), field capacity (pF 2.0) and saturation (respectively SOIL_MOISTURE_CONTENT_WP, SOIL_MOISTURE_CONTENT_FC and SOIL_MOISTURE_CONTENT_SAT in SOIL_PHYSICAL_GROUP). These volumetric soil moisture contents are important values of the water retention curve. They have been estimated in two steps within the SINFO study.
The starting point is the calculation of Soil Water Available for Plants (SWAP) with the CERU32 program of INRA which calculates the SWAP for each STU. For both, a top and sub soil layer, first the AWC is determined via rules covering texture class and packing density class. Next, the SWAP results from a multiplication of AWC and depth of the soil layer. If gravels or stones are present, a percentage of water is removed from the calculated SWAP. In the same manner, for taking account of capillary rises, an amount of water is added to the SWAP for particular substrata such as loess or chalk.
CGMS can only handle one water retention curve per STU. Therefore the vertical stratification of AWC-values has been translated into one AWC-value that has been weighed for different lengths of soil layers and their related AWC-values. In case of rocks, no information on texture class etc. the AWC is given a standard low value of 10 mm per 1 meter rooting depth.
To link the AWC values produced by the CERU32 program to soil physical groups the volumetric soil moisture content of wilting point is taken from the HYPRES database. This database covers basic soil data and soil hydraulic properties from a wide range of soils across Europe. Based on the data class pedo transfer functions have been set up for 11 different top and sub soil texture classes. They can be used to estimate volumetric soil moisture content of wilting point and field capacity.
The volumetric soil moisture content at field capacity is determined by taking the HYPRES based volumetric soil moisture content of wilting point and adding up the AWC value from the CERU32 program.
The volumetric soil moisture content at saturation is also taken from the HYPRES rules. This value is corrected when the difference between the volumetric soil moisture content at field capacity and saturation is less than 6% of the total soil volume.
Next, the distinct unique combinations of values of volumetric soil moisture content at wilting point, field capacity, saturation have been determined. This resulted in 743 unique groups.
Further, the soil map is used to exclude particular STU's in case these STU's are unsuitable because of a shallow rooting depth. Unsuitable STU's are determined per crop group. In the current CGMS STU's with a rooting depth < 40 cm have been excluded for the crop groups cereals/pulses, root crops and maize crops. In case of crop group forage no STU's are left out. The suitable STU's per crop group are stored in table SUITABILITY.
Initial available soil water
The table INITIAL_SOIL_WATER is used to supply data on initial ground water level and drainage depth. In case ground water influence is switched on, the initial soil moisture profile is not based on the WAV parameter (available water in potential rooting zone) but calculated assuming a equilibrium situation in relation to the ground water level. If the ground water level is deep the initial soil moisture profile will be very dry. To avoid such a dry start the ground water module will not be used if the initial ground water table (ZTI) is already deeper than 600 cm below soil surface. The parameters that describe the infiltration are stored in table SITE. They describe the redistribution or loss of rainfall due to run off and surface storage. These parameters are system wide and have no linkage with soil mapping units.
In case the aggregation is done through the soil suitability mode suitable soils are determined per crop group on the basis of crop growth limiting properties of these soils. Examples of limiting soil properties are slope, texture, agriculture limiting phase, rooting depth, drainage, salinity and alkalinity. Next, pedotransfer rules can be used to determine whether a soil is suitable for root crops, cereals and grain maize based on these limiting properties. The suitable STU’s and the percentage of the suitable area of SMU’s are available in the tables SUITABILITY and SMU_SUITABILITY. Because a SMU can consist of more than one STU the percentage suitable area must be calculated.
The spatial and temporal variability of initial soil moisture can be entered in the table INITIAL_SOIL_WATER. Two different issues can be set:
- The amount of available soil water (field WAV) used to initialize the potential rooting depth. Note that WAV is the amount of water added to the potential rooting depth in addition to the amount of water that is already stored at pressure head equals wilting point. When the available water is more than the potential root zone can contain, the surplus of the initial water is supposed to percolate to greater depth. For all crops except rice the maximum soil moisture content is the soil moisture content at field capacity while for rice it is the soil moisture content at saturation.
- The start of the soil water balance. The possible choices offered through the user interface are:
- No initialisation: no initialization and thus the soil water balance start at the emergence date.
- Automatic, use all weather prior to emergence: this means automated initialization using the available grid weather from the first day of the campaign. Note that the campaign year is defined in the user interface.
- Fixed number of days prior to emergence: specifies a fixed number of days of days prior to emergence. Note that the number is limited for the available grid weather from the first day of the campaign 25.
- Fixed date: in this case the CGMS reads the fixed date from the field GIVEN_STARTDATE_WATBAL in table INITIAL_SOIL_WATER.