The Danish Soil Classification From 1939 to 1975 the farmland area dropped from sqkm to sqkm It raised a need for soil maps for planning and administration purposes at national and county level The Danish government decided to finance a national soil mapping

The Danish Soil Classification : Soil mapping of the agriculture land mainly based on soil texture of the topsoil : Additional soil map on subsoil texture, landform and wetland and the establishment of a Danish pedological soil analytical database : Modelling and thematic maps

Basic requirements The areas should be classified on the basis of permanent stable characteristics There should be a national standard code of reference that would make it possible to classify as uniform as possible The results should clearly illustrate the range of fertile and infertile soils The maps should be made in such a way that they might be used in future regional planning The mapping should be finished within 3 years (price app Euro)

The soil map, scale 1: Classified area Texture of the plowlayer and subsoil (12 classes) Slope (3 classes) Subsoil geology (app. 50 classes) Not classified area Urban zone Forest Coastal dune sands, small arable areas, lakes etc

Organisation In December 1975 ADK was established to undertake the soil sampling, database handling and construction of the maps at scale 1: Crew: 3 AC and 1 technician + some students from the Universities. The soil sampling was done by local agronomists and the soil analyses were done at a research laboratory.

Mapping slopes and surface geology Slope classes Three slope classes delineated on topographic maps at scale 1: degrees Surface geology Dominant surface geology is shown in a 25ha grid based on the Danish geological surveys map which cover 75% of the country

Soil sampling for texture analyses ADK distributed topographic maps and questionnaires to local agronomists (advisors) who registered existing texture analyses The agronomists were asked to recommend suitable locations for forthcoming soil sampling ADK combined the recommendation with infor- mation on topography and surface geology and the final sampling sites were chosen The agronomists undertook the soil sampling topsoil samples (0-20cm) and 6000 subsoil samples (35-55cm) were taken

Sampling sites

Analyses Texture: 2 m, 20 m, (63 m), 200 m, 2000 m Hydrometer method and sieving Organic C: Determined by a Leco-apparatus Lime: Determined by treating the samples with HCl and capture the carbondioxide in bariumhydroxide

Texture analyses

Sample library

Texture classification

Map construction The borders on the soil maps were drawn by the crew at ADK in cooperation with the local agronomists The drawing of the borderlines was based on the texture analyses, landscape analyses, the surface geology maps and the local knowledge from the agronomists involved. The maps were digitized and all analytical data were stored in a database. The software was developed as a Ph.D. study at Århus University

Soil map from Aabenraa

Soil map of Ribe

Soil map of Denmark

Additional soil maps Geomorphological map Subsoil texture map Wetland map Potential acid sulfate soil Soil map of the forests

Geomorphological map of Denmark

Geological Surveys map of Gislum, 1:25000

Subsoil texture

Incircled wetlands on a topographic map

Wetlands

Soil chemical and physical data By combining the different soil maps an area can be characterized as follows: Topsoil: Fine sand (MCC2) Subsoil: loam (MCC5) Drainange: not wetland Geomorphology: Weichsel moraine In order to use the soil maps in planning there is a huge need for soil profile analytical data, chemical as well as physical

Profile sampling sites

Soil classification

Classification system The classification based exclusively on field observations. Describe the main pedological development within 120cm. Describe the presence of gley, lithic and limestone contact within 3 sections of the profile: 0-40, & cm Describe the thickness and carbon content of the A-horizon Describe the presence of fragipan, placic horizon, degradated B-horizons, cementation, calcic horizons

Danish soil classification system, soil orders

Danish soil classification system, soil groups Group leveI Lessive ranker* gley* podzol rendzin* pseudogley* brunjord degra stagnogley* brunsol blandings typi *begin at 40-80cm Example: Degralessive Podzolpseudogleytypilessive

Danish soil classification system, soil series Gley, lime and lithic contact in the soil section cm Placic horizon, fragipan, cementation, degradated Bt or Bs horizons, natric horizons, all within 1.2 meter depth entic A-horizons ( 20%OM. Example: kolluvial pseudogleyey Typilessive entic Degralessive

Soil name at order, group and series Podzol (A-E-Bh-Bs-C) 1)Typipodzol (gley > 120cm depth) 2) gleyey Typipodzol (gley cm) 3) Gleytypipodzol (gley 40-80cm) 4) Podzolgley (gley 0-40cm)

Danish pedological soil classification system

Transformation of soil names to figures

Finding special soil types Podzols with placic horizons Order 06; group 26 = all podzols + series 13 = placic Soils with Bt and lime beginning below cm Order 05; group 25 = soils with Bt + Series = lime beginning below 80 cm Soils with deep A-horizons Order 07 = A horizons deeper the 80 cm + series 01 = A horizons cm deep

Soil toposequence based on soil classification for every 25 meter on the pipeline

Profile description

Rendzinleptosol on Senon limestone Cambisol in calcareous loamy till

Luvisols

Podzoluvisols

Regosol and arenosol

Podzols

Gleysols

Inner marsh clay upon a podzol Fluvisol in outer marsh deposits

Histosols, one developed on a former podzol

Histosols

Soil profile description scheme

Analyses Texture (hydrometer + sieving) Total carbon (dry combustion) Total nitrogen (Kjeldahl) Total organic and inorganic phosphorous pH(H 2 O) and pH(CaCl 2 ) Lime content (Scheibler) Exchangeable acidity at pH 8.1 (Pipers method) Exchangeable bases (NH 4 Ac-extraction at pH7) DCB, oxalate and pyrophosphate iron and aluminium KCl-extractable H and Al Soil water retention (Pressure plate apparatus)

The use of the databases Protection of fertile farmland around towns Irrigation need for agriculture production at county level Irrigation permission Hunting zones Economical compensation for drainage The potential drainage need at national level Mapping of potential set aside area Carbon storage in Danish soils Nitrate leaching from farmland Potentially acid sulfate soil

Example of rules for irrigation permission Ribe County If a farmer wants to irrigate his fields he has to get a soil texture analyses of the plowlayer and send it to the county administration. They use the following equation derived from the soil profile analytical database PAW: 2.34*OM% *clay *silt *FS If PAW < 20 the farmer may irrigate with 100mm/ha If PAW is the farmer may irrigate with 75mm/ha If PAW is >30 the farmer may irrigate with 50mm/ha

Root Zone Capacity Based on the texture analyses from the Danish Soil Classification and the geological map, soil profiles at sites are constructed with texture in the depth: 0-30 cm, cm and cm. Based on the soil profile analytical database the following equations between water content at FC and PWP (vol%) can be established: FC=2.34*%OM *%clay *%silt %*FS , r 2 =0.84 PWP=0.55*%OM *%clay *silt r 2 =0.89 Based on root studies an effective root depth for crops in relation to soil type can be determined and RZC for water in mm can be calculated

Root zone capacity for barley

Mean irrigation need for barley production

Potential drainage need

Set aside areas in Denmark

FAO 1974 soil map

EC-soil map scale 1:

FAO 1990

FAO-soil types on sandy parent materials

FAO-soil map

FAO Soil Map Denmark

FAO-legend

FAO soil types in relation to landform

Soil analytical data, proforma 1

Soil analytical data, proforma 2