FAO Guidelines for Soil Description (2006)

I. Site Information

Site information refers to the data on the bio-physical characteristics of the site where the soil

to be examined is located including the name of the person doing the soil examination and the

date of examination.

a) Profile number

It is necessary to assign a profile number to each soil examined to allow easy and simple

retrieval of profile descriptions from computerised data storage systems.

b) Author(s)

The person who performs the description needs to be properly acknowledged in future uses of

the soil data and he or she holds responsibility for the quality of the data.

c) Date of description

The date of description is an important information and should be given as yymmdd (6 digits).

d) Location

This should include the distance (in meters or kilometers) and direction to the site from

permanent features which are recognizable in the field and on the topographic map.

e) Elevation

The elevation (in meters) of the site relative to sea level should be obtained from detailed

contour or topographic maps or by altimeter readings. At present determination of elevation

by a Global Positioning System (GPS) unit is inaccurate and unacceptable.

f) Map sheet number and Coordinates

The number of the topographic map sheet, preferably at 1 : 25 000 or 1 : 50 000 scale, on

which the soil observation occurs should be given. The latitude and longitude of the site (in

degrees, minutes, seconds and decimal seconds) can be derived directly from topographic

maps or a Global Positioning System (GPS) unit.

g) Atmospheric climate and weather conditions

Present weather conditions

Sunny/clear Partly cloudy Overcast

Rain Sleet Snow

Past weather conditions

No rain during the last month

No rain during the last week

No rain during the last 24 hours

Small rain during the last 24 hours

Stronger rain since some days or rainstorm during the last 24 hours

Extremely rainy time or snow melting

h) Soil climate

Soil temperature regime Soil moisture regime

Pergelic Aquic

Cryic Peraquic

Frigid Isofrigid Aridic

Mesic Isomesic Udic

Thermic Isothermic Perudic

Hyperthermic Isohyperthermic Ustic

Xeric and Torric

i) Landform and topography (relief)

Major landform

Landforms should be described by their morphology and not by their genetic origin, or

processes responsible for their shape.

1st Level 2

nd Level Gradient Relief Intensity

[%] (m km-1

)

Level land plain <10 <50

plateau <10 <50

depression <10 <50

valley floor <10 <50

Sloping land medium-gradient mountain 15-30 150-300

medium-gradient hill 10-30 100-150

medium-grad. escarpment zone 10-30 50-100

medium-gradient valley 10-30 100-150

dissected plain 10-30 50-100

Steep land high-gradient mountain >30 >300

high-gradient hill >30 150-130

high-gradient escarpment zone >30 150-130

high gradient valleys >30 >150

Slope position

Slope positions in undulating and mountainous terrain (redrawn from Schoeneberger et al.

1998)

CR = Crest (summit)

UP = Upper slope (shoulder)

MS = Middle slope (backslope)

LS = Lower slope (footslope)

TS = Toeslope

BO = Bottom (flat)

Slope form

Straight

Concave

Convex

Terraced

Complex (Irregular)

Slope gradient and orientation

Flat 0 - 0.2 % Sloping 5 - 10 %

Level 0.2 - 0.5 % Strongly sloping 10 - 15 %

Nearly level 0.5 - 1.0 % Moderately steep 15 - 30 %

Very gently sloping 1.0 - 2 % Steep 30 - 60 %

Gently sloping 2 - 5 % Very steep >60 %

The orientation which a slope is facing is coded with N for north, E for east, S for south and

W for west. SSW e.g. means south south-west.

j) Land use and vegetation

Land use

Settlement, industry Residential use Industrial use Transport Recreational use Excavations

Crop Agriculture

Annual field cropping Shifting cultivation Fallow system cultivation Ley system cultivation Rainfed arable cultivation Wet rice cultivation Irrigated cultivation

Perennial field cropping Non-irrigated cultivation Irrigated cultivation

Tree and shrub cropping Non-irrigated tree crop cultivation Irrigated tree crop cultivation Non-irrigated shrub crop cultivation Irrigated shrub crop cultivation

Animal Husbandry

Extensive grazing Nomadism Semi-nomadism Ranching

Intensive Grazing Animal production Dairying

Forestry

Natural forest and woodland Selective felling Clear felling

Plantation forestry

Mixed farming Agro-forestry Agro-pastoralism

Extraction and collection Exploitation of natural vegetation Hunting and fishing

Nature Protection Nature a. game preservation Reserves Parks Wildlife management

Degradation control Without interference With interference

Not used and not managed

Additional codes may be used to further specify the land utilization type. For example:

Rainfed arable cultivation Traditional Improved traditional Mechanized traditional Commercial Unspecified

For arable land use, the dominant crops which are grown should be mentioned, and as much

information as possible given on soil management, use of fertilizers, duration of fallow period,

rotation systems and yields.

Crops

Crops are plants that are cultivated for their economic value.

Barley

Beans

Cassava

Coconut

Coffee

Cashew

Cocoa

Cowpea

Cotton

Fruit trees

Groundnut

Maize

Millet

Oilpalm

Peas

Potato

Rice (flooded)

Rice

Rubber

Rice (upland)

Soyabean

Sugar cane

Sunflower

Sorghum

Sweet potato

Tobacco

Tea

Vegetables

Wheat

Yams

Human influence

This refers to the influence of humans on the site. Examples of human influences are:

No influence Bunding

Not known Burning

Vegetation slightly disturbed Terracing

Vegetation moderately disturbed Ploughing

Vegetation strongly disturbed Plaggen

Vegetation disturbed Raised beds

Sprinkler irrigation Sand additions

Furrow irrigation Mineral additions (unspecified)

Flood irrigation Pollution

Border irrigation Clearing

Irrigation (unspecified) Surface compaction

Artificial drainage Borrow pit

Application of fertilizers

Vegetation

Closed Forest 1)

Evergreen forest

Semi-deciduous forest

Deciduous forest

Xeromorphic forest

Woodland 2)

Evergreen woodland

Semi-deciduous woodland

Deciduous woodland

Xeromorphic woodland

1) Continuous tree layer, crowns overlapping,

large number of tree and shrub species in

distinct layers

2) Continuous tree layer, crowns usually not

touching, understorey may be present

Shrub

Evergreen shrub

Semi-deciduous shrub

Deciduous shrub

Xeromorphic shrub

Dwarf Shrub Evergreen dwarf shrub

Semi-deciduous dwarf shrub

Deciduous dwarf shrub

Xermomorphic dwarf shrub Tundra

Herbaceous Tall grassland

Medium grassland

Short grassland

Forb

In addition, other characteristics of the vegetation, such as height of trees or canopy cover,

may be recorded.

k) Parent material

Hierarchy of lithology

Major Class Group Type

Igneous rock acid igneous granite grano-diorite quartz-diorite rhyolite

intermediate andesite, trachyte, phonolite igneous diorite-syenite

basic igneous gabbro basalt dolerite

ultrabasic igneous peridotite pyroxenite ilmenite, magnetite, ironstone, serpentine

pyroclastic tuff, tuffite

volcanic scoria, breccia

volcanic ash

ignimbrite

Metamorphic acid metamorphic quartzite rock gneiss, migmatite slate, phyllite (pelitic rocks) schist

basic metamorphic slate, phyllite (pelitic rocks) green schist gneiss rich in Fe-Mg-minerals metamorphic limestone (marble)

Sedimentary clastic sediments conglomerate, breccia rock (consolidated) sandstone, greywacke, arkose silt-, mud-, claystone shale ironstone

carbonatic, organic limestone, other carbonate rock marl & other mixtures coals, bitumen & related rocks

evaporites anhydrite, gypsum halite

Sedimentary (unconsolidated)

fluvial sand and gravel clay, silt and loam

lacustrine sand silt and clay

marine, estuarine sand clay and silt

colluvial slope deposits

lahar

eolian loess sand

glacial moraine glacio-fluvial sand

glacio-fluvial gravel

kryogenic periglacial rock debris periglacial solifluction layer

organic rainwater-fed moor peat groundwater-fed bog peat

anthropogenic/ redeposited natural material technogenic industrial depsoit

unspecified clay deposits loam and silt sand gravelly sand grave, broken rock

l) Age of the land surface

Very young (1-10 years) anthropogeomorphic: with complete disturbance of natural surfaces

(and soils) like in urban, industrial and mining areas with very early soil development

from fresh natural or technogenic or mixed materials.

Very young (1-10 years) natural: with erosional loss or deposition of materials like on tidal

flats, of coastal dunes, in river valleys, landslides or desert areas

Young (10-100 years) natural: with erosional loss or deposition of materials like on tidal flats,

of coastal dunes, river valleys, landslides, or desert areas,

Young (10-100 years) anthropogeomorphic: with complete disturbance of any natural

surfaces (and soils) like in urban, industrial and mining areas with early soil

development from fresh natural or technogenic or mixed materials, or restriction of

flooding by dikes

Holocene (100-10,000 years) anthropogeomorphic: man- made relief modifications, like

terracing of forming hills or walls by early civilisations or during Middle Age or

earlier, or restriction of flooding by dikes

Holocene (100-10,000 years) natural: with erosional loss or deposition of materials like on

tidal flats, of coastal dunes, in river valleys, landslides or desert areas,

Late Pleistocene, ice covered, commonly the recent soil formation on fresh materials

Late Pleistocene, periglacial, commonly the recent soil formation on preweathered materials

Late Pleistocene; without periglacial influence

Older Pleistocene, ice covered, commonly the recent soil formation on younger over older

and preweathered materials

Older Pleistocene, with periglacial influence, commonly the recent soil formation on younger

over older and preweathered materials

Older Pleistocene without periglacial influence

Tertiary land surfaces, commonly high planes, terraces or peneplains, except incised valleys,

frequent occurrence of paleosoils

Older land surfaces, commonly high planes, terraces or peneplains, except incised valleys,

frequent occurrence of paleosoils

II. Soil profile description

1. Soil surface characteristics

a) Rock outcrops

Rock outcrops can limit the use of modern, mechanized, agricultural equipment. This can be

described using the table below:

Surface cover Distance between rock outcrops

None

Very few

Few

Common

Many

Abundant

Dominant

0 %

0 – 2 %

2 – 5 %

5 – 15 %

15 – 40 %

40 – 80 %

>80 %

>50 m

20 – 50 m

5 – 20 m

2 – 5 m

<2 m

b) Surface coarse fragments

Surface coarse fragments should be described using the table below:

Surface cover Size classes indicating the greatest dimension

None

Very few

Few

Common

Many

Abundant

Dominant

0 %

0 – 2 %

2 – 5 %

5 – 15 %

15 – 40 %

40 – 80 %

>80 %

Fine gravel 0.2– 0.6cm

Medium gravel 0.6– 2.0cm

Coarse gravel 2 – 6 cm

Stones 6 – 20 cm

Boulders 20 – 60 cm

Large boulders 60 –200 cm

c) Erosion

Main categories of erosion

No evidence of erosion

Water erosion or deposition Wind (eolian) erosion or deposition

Sheet erosion Wind deposition

Rill erosion Wind erosion and deposition

Gully erosion Shifting sands

Tunnel erosion Salt deposition

Deposition by water Water and wind erosion

Mass movement (landslides and similar phenomena)

Not known

Area affected

The total area affected by erosion and deposition is estimated following the classes below:

0 % 10 – 25 %

0 – 5 % 25 – 50 %

5 – 10 % > 50 %

Degree

Slight: Some evidence of damage to surface horizons. Original biotic functions

largely intact.

Moderate: Clear evidence of removal of surface horizons. Original biotic func-

tions partly destroyed.

Severe: Surface horizons completely removed and subsurface horizons exposed.

Original biotic functions largely destroyed.

Extreme: Substantial removal of deeper subsurface horizons (badlands). Original

biotic functions fully destroyed.

d) Surface sealing

Surface sealing refers to crusts which develop at the soil surface after the topsoil dries out.

Thickness Consistency

None Slightly hard

Thin <2 mm Hard

Medium 2 – 5 mm Very hard

Thick 5 – 20 mm Extremely hard

Very thick >20 mm

e) Surface cracks

Surface cracks develop in shrink-swell clayey soils after they dry out. They indicate the

dominance of expanding type of clay particularly montmorillonite.

Width Distance between cracks

Fine < 1 cm Very closely spaced <0.2 m

Medium 1 – 2 cm Closely spaced 0.2 – 0.5 m

Wide 2 – 5 cm Moderately widely spaced 0.5 – 2 m

Very wide 5 – 10 cm Widely spaced 2 – 5 m

Extremely wide > 10 cm Very widely spaced >5 m

2. Soil horizon characteristics

Subordinate characteristics within master horizons

a Highly decomposed organic material

b Buried genetic horizon

c Concentrations1 or nodules

d Dense layer (physically root restrictive)

e Moderately decomposed organic material

f Frozen soil

g Stagnic horizons2

h Accumulation of organic matter in mineral horizons

i Slightly decomposed organic material

j Jarosite accumulation

k Accumulation of pedogenic carbonates

l Capillary fringe mottling

m Strong cementation (pedogenic, massive)

n Pedogenetic accumulation of exchangeable sodium

o Residual accumulation of sesquioxides

p Plowing or other human disturbance

q Accumulation of pedogenetic silica

r Strong reduction3

t Illuvial accumulation of silicate clay

u Urban and other human-made materials

v Occurrence of plinthite

w Development of color or structure

x Fragipan characteristics

y Pedogenetic accumulation gypsum

z Pedogenetic accumulation of salts more soluble than gypsum

Note: In the USDA method, concentration1 is called concretions, g indicates strong gleying

2,

and r indicates weathered or soft bedrock3

a) Horizon boundary

Depth

Distinctness and topography

Abrupt 0 - 2 cm

Clear 2 - 5 cm

Gradual 5 - 15 cm

Diffuse > 15 cm

The topography of the boundary indicates the

smoothness of depth variation of the boundary

Smooth Nearly plane surface

Wavy Pockets less deep than wide

Irregular Pockets more deep than wide

Broken Discontinuous

b) Soil texture

Field estimation of textural classes

The soil textural class can be estimated in the field by easy field tests. For this, the soil sample

must be in a moist to weak wet state. Gravel and plant materials >2 mm must be removed.

Clay: makes fingers dirty, is cohesive (sticky), is formable, has a high plasticity and has a

shiny surface after squeezing between fingers.

Silt: makes fingers dirty, is nonsticky, only weak formable, has a rough and ripped surface

after squeezing between fingers and feels very floury (like talcum powder).

Sand: can not be formed, makes fingers not dirty and feels very grainy.

Key to the soil texture classes (adapted from Schlichting et al., 1995)

1. Not possible to roll a wire of about 7 mm Ø (about Ø of a pencil)~% clay

1.1 not dirty, not floury, no fine material in the finger rills sand <5

- if grain sizes are mixed unsorted sand <5

- if most grains are very coarse (>0.6 mm) coarse sand <5

- if most grains are of medium size (0.2-0.6 mm) medium sand <5

- if most grains are of fine size (<0.2 mm) but still grainy fine sand <5

- if most grains are of very fine size (<0.12 mm), tending

to be floury very fine sand <5

1.2 not floury, grainy, scarcely fine material in the finger rills,

weakly shapeable, adheres slightly to the fingers loamy sand <12

1.3 as 1.2 but moderately floury, sandy loam (clay poor) <10

2. Possible to roll a wire of about 7 to 3 mm Ø (about ½ Ø of a pencil) but breaks if trying

to form a ring, moderate cohesive, adheres to the fingers

2.1 very floury and not cohesive

- some grains to feel silt loam (clay poor) <10

- no grains to feel silt <12

2.2 moderately cohesive, adheres to the fingers, has a rough and ripped surface after

squeezing between fingers and

- very grainy and not sticky sandy loam (clay rich) 10-25

- has moderate sand grains loam 8-27

- not grainy but distinctly floury and somewhat sticky silt loam (clay rich) 10-27

2.3 has a rough and moderate shiny surface after squeezing between fingers and is sticky

and grainy to very grainy sandy clay loam 20-35

3. Possible to roll a wire smaller than 3 mm (less than ½ Ø of a pencil) and to form the

wire to a ring of about 2-3 cm Ø, cohesive, sticky, gnash between teeth, has a moderate

shiny surface after squeezing between fingers

3.1 very grainy sandy clay 35-55

3.2 grains can be seen and felt clay loam 25-40

3.3 no grains to see and to feel, low plasticity silty clay loam 25-40

3.4 no grains to see and to feel, high plasticity silty clay 40-60

4. Has a shiny surface after squeezing between fingers and a high plasticity

4.1 some grains to see or to feel, gnashes between teeth clay 40-60

4.2 no grains to see or to feel, does not gnash between teeth heavy clay >60

c) Rock fragments

Abundance (by volume), for estimation see Figure 5

None 0 %

Very few 0 - 2 %

Few 2 - 5 %

Common 5 - 15 %

Many 15 - 40 %

Abundant 40 - 80 %

Dominant >80 %

Charts for estimating proportions of coarse fragments and mottles

Size of rock fragments

Rock Particle Size

Fine gravel 0.2-0.6 cm

Medium gravel 0.6- 2 cm

Coarse gravel 2 - 6 cm

Stones 6 - 20 cm

Boulders 20 - 60 cm

Large boulders >60 cm

Shape of rock fragments

25 % 30 %

40 % 50 % 75 % 90 %

1 % 3 % 5 % 10 %

15 % 20 %

The general shape or roundness may be described using the following terms:

Flat Subrounded

Angular Rounded

State of weathering of rock fragments

The state of weathering of the coarse fragments is described as follows:

Fresh or slightly weathered: fragments show little or no signs of weathering

Weathered: partial weathering is indicated by discolouration and loss of crystal

form in the outer parts of the fragments while the centres remain relatively fresh

and the fragments have lost little of their original strength.

Strongly weathered: all but the most resistant minerals are weathered, strongly

discoloured and altered throughout the fragments, which tend to disintegrate

under only moderate pressure.

d) Soil color

Hue is the dominant spectral colour (red, yellow, green, blue, violet).

Value is the lightness or darkness of colour ranging from 1 (dark) to 8 (light).

Chroma is the purity or strength of colour ranging from 1 (pale) to 8 (bright).

If there is no dominant soil matrix color, the horizon is described as mottled and two or more

colors are given. In addition to the colour notations, the standard Munsell color names may be

given.

e) Mottling

Color of mottles

Abundance of mottles

None 0 % Common 5 - 15 % Very few 0 - 2 % Many 15 - 40 % Few 2 - 5 % Abundant >40 %

Size of mottles

Very fine <2 mm Medium 6 - 20 mm Fine 2 - 6 mm Coarse >20 mm

Contrast of mottles

The color contrast between mottles and soil matrix can be described as follows:

Faint: The mottles are evident only on close examination. Soil colors in both the matrix and mottles have closely related hues, chromas and values.

Distinct: Although not striking, the mottles are readily seen. The hue, chroma or value of the matrix are easily distinguished from those of the mottles. They may vary by as much as 2.5 units of hue or several units in chroma or value.

Prominent: The mottles are conspicuous and mottling is one of the outstanding features of the horizon. Hue chroma and value alone or in combination are at least several units apart.

f) Redoximorphic properties

Redoximorphic (or reductimorphic) properties of the soil matrix reflect permanently wet or at

least reduced conditions. They are expressed by neutral (white to black: Munsell N1 to N) or

bluish to greenish colours (Munsell 2.5Y, 5Y, 5G, 5B). The color pattern will often change by

aeration in minutes to days, due to oxidation processes.

Redoximorphic color pattern and occurrence of Fe compounds

Color Munsell Color Formula Mineral

Greyish green, light blue 5GY-5B2-3/1-3 FeII/Fe

III Fe-mix-compounds

(blue green rust)

White, after oxidation

brown N7-8 → 10YR4/5 FeCO3 siderite

White, after oxidation blue N7-8 → 5B Fe3(PO4) · 8 H2O vivianite

Bluish black

(w. 10% HCl H2S- smell) 5-10B1-2/1-3 FeS (or Fe3F4) Fe- sulphides

White, after oxidation white N8 → N8 - Complete loss of Fe-

compounds

g) Carbonates

CaCO3 Content Class Reaction

0 % Non-calcareous: No detectable visible or audible

effervescence.

0 - 2 % Slightly calcareous: Audible effervescence but not visible.

2 -10 % Moderately calcareous: Visible effervescence.

10 -25 % Strongly calcareous: Strong visible effervescence. Bubbles

form a low foam.

>25 % Extremely calcareous: Extremely strong reaction. Thick foam

forms quickly.

i) Readily soluble salts

Certain soils like coastal or desert soils can be enriched with water soluble salts or salts more

soluble than gypsum. The salt content of the soil can be estimated from an electrical

conductivity (EC in dS m-1

= mS cm-1

) measurement on a saturated soil paste or a more dilute

suspension of soil in water. Conventionally EC is measured in the laboratory in the saturation

extract (ECSE) and most classification values as well as data about salt sensitivity of crops

refer to ECSE.

ECSE

(dS m-1

at 25 ºC)

Not salty <0.75

Slightly salty 0.75 - 2

Moderately salty 2 - 4

Strongly salty 4 - 8

Very strongly salty 8 –15

Extremely salty >15

j) Field soil pH

In the field, pH is either estimated using indicator papers or measured with a portable pH

meter in a soil suspension (1 part soil and 2.5 part H20, 1 M KCl or 0.1M CaCl2 solution).

After shaking the solution and waiting for 15 minutes the pH value can be read. For the

measurement use a transparent 50 ml plastic cup with marks for 8 cm3 soil (~ 10 g) and 25 ml

water.

pH value

Very strongly alkaline >9.0

Strongly alkaline 8.5-9.0

Moderately alkaline 7.9-8.4

Mildly alkaline 7.4-7.8

Neutral 6.6-7.3

Slightly acid 6.1-6.5

Medium acid 5.6-6.0

Strongly acid 5.1-5.5

Very strongly acid 4.5-5.0

Extremely acid <4.5

k) Soil structure

Grade

Weak: Aggregates are barely observable in place and there is only a weak arrangement of

natural surfaces of weakness. When gently disturbed, the soil material breaks into a

mixture of few entire aggregates, many broken aggregates, and much material without

aggregate faces.

Moderate: Aggregates are observable in place and there is a distinct arrangement of natural

surfaces of weakness. When disturbed, the soil material breaks into a mixture of many

entire aggregates, some broken aggregates, and little material without aggregates faces.

Strong: Aggregates are clearly observable in place and there is a prominent arrangement of

natural surfaces of weakness. When disturbed, the soil material separates mainly into

entire aggregates.

The following classes may be used to describe soil structure:

Very weak Combined classes may be constructed as follows: Weak Weak to moderate Moderate Moderate to strong

Strong Very strong

Size

Class Platy Prismatic Blocky Granular mm mm mm mm

Very fine < 1 < 10 < 5 < 1 Fine 1 - 2 10 - 20 5 - 10 1 - 2 Medium 2 - 5 20 - 50 10 - 20 2 - 5 Coarse 5 - 10 50 - 100 20 - 50 5 – 10 Very coarse > 10 > 100 > 50 > 10

Combined classes may be constructed as follows:

Fine and very fine Coarse and very coarse Fine and medium Fine to coarse Medium to very coarse Medium and coarse

Type

Granular: Spheroids or polyhedrons, having curved or irregular surfaces which are not casts

of the faces of surrounding aggregates.

Blocky: Blocks or polyhedrons, nearly equidimensional, having flat or slightly rounded

surfaces which are casts of the faces of the surrounding aggregates. Subdivision is

recommended into angular blocky, with faces intersecting at relatively sharp angles, and

subangular blocky faces intersecting at rounded angles.

Prismatic: the dimensions are limited in the horizontal and extended along the vertical plane;

vertical faces well defined; having flat or slightly rounded surfaces which are casts of

the faces of the surrounding aggregates. Faces normally intersect at relatively sharp

angles. Prismatic structures with rounded caps are distinguished as Columnar.

Platy: Flat with vertical dimensions limited; generally oriented on a horizontal plane and

usually overlapping.

l) Consistence

Consistence when dry

This is determined by breaking an air-dried mass of soil between thumb and forefinger or in

the hand.

Loose: Non-coherent

Soft: Soil mass is very weakly coherent and fragile; breaks to powder or

individual grains under very slight pressure

Slightly hard: Weakly resistant to pressure; easily broken between thumb and

forefinger.

Hard: Moderately resistant to pressure; can be broken in the hands; not

breakable between thumb and forefinger.

Very hard: Very resistant to pressure; can be broken in the hands only with

difficulty.

Extremely hard: Extremely resistant to pressure; cannot be broken in the hands.

Additional description:

Soft to slightly hard

Slightly hard to hard

Hard to very hard

Consistence when moist

This is determined by attempting to crush a mass of moist or slightly moist soil material. This

is the usual condition in the field except in poorly drained soils or immediately after a heavy

rain.

Loose: Non-coherent

Very friable: Soil material crushes under very gentle pressure, but coheres when

pressed together.

Friable: Soil material crushes easily under gentle to moderate pressure between

thumb and forefinger, and coheres when pressed together.

Firm: Soil material crushes under moderate pressure between thumb and

forefinger, but resistance is distinctly noticeable.

Very firm: Soil material crushes under strong pressures; barely crushable

between thumb and forefinger.

Extremely firm: Soil material crushes only under very strong pressure; can not

be crushed between thumb and forefinger.

Additional description:

Very friable to friable

Friable to firm

Firm to very firm

Consistence when wet: maximum stickiness and maximum plasticity

Stickiness is the quality of adhesion of the soil material to other objects determined by noting

the adherence of soil material when it is pressed between thumb and finger.

Non sticky: after release of pressure, practically no soil material adheres to

thumb and finger.

Slightly sticky: after pressure, soil material adheres to both thumb and finger but

comes off one or the other rather cleanly. It is not appreciably

stretched when the digits are separated.

Sticky: after pressure, soil material adheres to both thumb and finger and tends

to stretch somewhat and pull apart rather than pulling free from either

digit.

Very sticky: after pressure, soil material adheres strongly to both thumb and

finger and is decidedly stretched when they are separated.

Additional description:

Slightly sticky to sticky

Sticky to very sticky

Plasticity is the ability of soil material to change shape continuously under the influence of an

applied stress and to retain the compressed shape after removal of stress. Determined by

rolling the soil in the hands until a wire about 3 mm in diameter has been formed.

Non plastic: No wire is formable

Slightly plastic: Wire formable but immediately breaks if bent into a ring; soil

mass deformed by very slight force.

Plastic: Wire formable but breaks if bent into a ring; slight to moderate force

required for deformation of the soil mass.

Very plastic: Wire formable and can be bent into a ring; moderately strong to

very strong force required for deformation of the soil mass.

m) Soil moisture

The soil moisture condition of the soil in the field can be estimated by the simple procedure of

Schlichting et al. (1995):

Crushing Forming (to a ball) Moistening Rubbing (in the hand) Moisture pF *)

dusty or

hard

not possible,

seems to be warm

getting very

dark not lighter very dry 5

makes no

dust

not possible,

seems to be warm

getting dark hardly lighter dry 4

makes no

dust possible (not sand)

getting

slightly dark obviously lighter

slightly

moist 3

is sticky finger moist and

cool, weakly shiny

no change of

colour obviously lighter moist 2

free water drops of water no change of

color

wet 1

free water drops of water

without crushing

no change of

color

very wet 0

*) pF (p = potential, F = free energy of water) is log hPa

m) Bulk density

Field estimation of bulk density for mineral soils (Schlichting et al., 1995)

Observation Structure Bulk Density

[g cm-3

]

Sandy, silty and loamy soils with low clay content

Many pores, moist materials drop easy out of the

auger; materials with vesicular pores, mineral soils

with andic properties.

granular <0.9

Sample disintegrates at the instant of sampling, many

pores visible on the pit wall. single grain, granular

0.9-1.2

Sample disintegrates into numerous fragments after

application of weak pressure.

single grain, suban-

gular, angular blocky

1.2-1.4

Knife can be pushed into the moist soil with weak

pressure, sample disintegrates into few fragments,

which may be further divided.

subangular and

angular blocky,

prismatic, platy

1.4-1.6

Knife penetrates only 1-2 cm into the moist soil, some

effort required, sample disintegrates into few

fragments, which cannot be subdivided further.

prismatic, platy,

(angular blocky)

1.6-1.8

Very large pressure necessary to force knife into the

soil, no further disintegration of sample. prismatic,

>1.8

Loamy soils with high clay content, clayey soils

When dropped, sample disintegrates into numerous

fragments, further disintegration of subfragments after

application of weak pressure.

angular blocky 1.0-1.2

When dropped, sample disintegrates into few

fragments, further disintegration of subfragments after

application of mild pressure.

angular blocky,

prismatic, platy,

columnar

1.2-1.4

Sample remains mostly intact when dropped, further

disintegration possible after application of large

pressure.

coherent, prismatic,

platy, (columnar, an-

gular blocky, platy)

1.4-1.6

Sample remains intact when dropped, no further

disintegration after application of very large pressure.

coherent (prismatic,

columnar)

>1.6

If organic matter content is >2%, bulk density has to be reduced by 0.03 g cm-3

for each %

increment of organic matter content.

n) Voids (Porosity)

Type

There is a large variety in the shape and origin of voids. The major types of voids may

be classified in a simplified way as follows:

Interstitial: Predominantly irregular and interconnected, generally the voids

between sand grains and rock fragments.

Vesicles: Discontinuous spherical or elliptical voids (chambers) of sedimentary

origin or formed by compressed air, for instance gas bubbles in

slaking crusts after heavy rainfall.

Vughs: Mostly irregular, equidimensional voids of faunal origin or resulting from

tillage or disturbance of other voids. Discontinuous or interconnected.

Channels: Elongate voids of faunal or floral origin. Mostly of tubular shape and

continuous, strongly varying in diameter.

Size

The diameter of the elongate or tubular voids is described using the following classes:

Very fine < 0.5 mm

Fine 0.5 - 2 mm

Medium 2 - 5 mm

Coarse 5 - 20 mm

Very coarse 20 - 50 mm

Abundance

The abundance of fine and very fine elongate pores as one group and of medium and coarse

pores as another is recorded as the number per unit area of a square decimeter.

< 2 mm > 2 mm

None 0 0

Very few 1 - 20 1- 2

Few 20 - 50 2- 5

Common 50 - 200 5- 20

q) Roots

The abundance of fine and very fine roots may be recorded similarly as for voids (see Figure

9), expressed in the number of roots per square decimetre.

Size (diameter)

Very fine < 0.5 mm

Fine 0.5 - 2 mm

Medium 2 - 5 mm

Coarse > 5 mm

Size

Abundance

very few few common

very fine(<0.5 mm)

fine(0.5-2 mm)

medium(2-5 mm)

1cm

Abundance

< 2 mm > 2 mm

None 0 0

Very few 1 - 20 1- 2

Few 20 - 50 2- 5

Common 50 - 200 5- 20

Many >200 >20

r) Other biological features

Biological features such as krotovinas, termite burrows, insect nests, worm casts or burrows

of larger animals are described in terms of abundance and kind. In addition, specific locations,

patterns, size, composition or any other characteristic may be recorded.

Abundance

Abundance of biological activity is recorded in the following general descriptive terms:

None Common

Few Many

Kind

Examples of biological features are the following:

Artefacts Earthworm channels

Burrows (unspecified) Pedotubules

Open large burrows Termite or ant channels and nests

Infilled large burrows Other insect activity

Charcoal

------------

Vbasio,SS212, Nov2013