The Danish Soil Classification

• From 1939 to 1975 the farmland area dropped from 32.000 sqkm to 28.000 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

• 1975-1980: Soil mapping of the agriculture land mainly based on soil texture of the topsoil

• 1980-1985: Additional soil map on subsoil texture, landform and wetland and the establishment of a Danish pedological soil analytical database

• 1985-1990: 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. 600.000 Euro)

The soil map, scale 1:50.000

• 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 1:50.000.

• 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 1:25000 <6 degrees, 6-12 degrees and >12 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. 36000 topsoil samples (0-20cm) and 6000 subsoil samples (35-55cm) were taken

Samplingsites

Analyses

Texture: 2m, 20m, (63m), 200m, 2000m

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 1980-1985

• 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 contactwithin 3 sections of the profile: 0-40, 40-80 & 80-120 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 1 2 3

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 80-120 cm

• Placic horizon, fragipan, cementation, degradated Bt or Bs horizons, natric horizons, all within 1.2 meter depth

• entic A-horizons (<10cm), kolluvial A horizon (40-80cm) humus poor A-horizon (10-40cm thick and <1% OM), humus rich A-horizon (10-40cm thick and 7-20% OM), histic O-horizon 10-40 cm thick and >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 80-120cm)

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 80-120 cm

Order 05; group 25 = soils with Bt +

Series 16 + 17 = lime beginning below 80 cm

Soils with deep A-horizons

Order 07 = A horizons deeper the 80 cm +

series 01 = A horizons 40-80 cm deep

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

Profile description

Rendzinleptosol on Senon limestoneCambisol in calcareous loamy till

Luvisols

Podzoluvisols

Regosol and arenosol

Podzols

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(H2O) and pH(CaCl2)• Lime content (Scheibler)• Exchangeable acidity at pH 8.1 (Pipers method)• Exchangeable bases (NH4Ac-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% + 0.70*clay + 0.47*silt + 0.18*FS + 3.68

If PAW < 20 the farmer may irrigate with 100mm/ha

If PAW is 20-30 the farmer may irrigate with 75mm/ha

If PAW is >30 the farmer may irrigate with 50mm/ha

Root Zone CapacityBased on the texture analyses from the Danish Soil Classification and

the geological map, soil profiles at 36.000 sites are constructed with

texture in the depth: 0-30 cm, 30-60 cm and 60-120 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 + 0.70*%clay + 0.47*%silt + 0.18%*FS + 3.68, r2=0.84

PWP=0.55*%OM + 0.63*%clay + 0.18*silt + 1.12 r2=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 1:1.000.000 - 1985

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