Soil Profile, Classification and Physical Properties

Soils & Fertilizers for Master Gardeners In-service Training

June 9, 2008

Amy ShoberUF/IFAS Gulf Coast REC

What is a Soil?

A natural body comprised of solids, liquid and gas that occur on the land surface.

Photo credits: USDA-NRCS

The Soil Profile• A horizon – Surface layer

w/ organic matter• E horizon – Leached

horizon between the A and B horizons

• B horizon – Zone of accumulation of material transported from the A and B horizons

• C horizon – Parent material

Florida State Soil

Photo Credits: Mary Collins, UF-IFAS

Myakka fine sand

Soil Taxonomy

Twelve Soil Orders

• Alfisols – Soils with subsurface clay accumulation; medium to high amount of bases (Ca, Mg, K, and Na)

• Andisols – Soils formed in volcanic ash

• Aridisols – Carbonate soils of arid environments with subsurface development

• Entisols – Soils with little or no horizon development

Twelve Soil Orders

• Histosols – Organic soils• Inceptisols – Soils with weakly

developed subsurface horizons• Gelisols – Soils with permafrost

within 2 meters of the surface• Mollisols – Grassland soils with high

base status

Twelve Soil Orders• Oxisols – Intensely weather (sub)tropical

soils• Spodosols – Acidic forest soils with

subsurface accumulation of metals/organic matter

• Vertisols – Clayey soils that shrink/swell• Ultisols – Strongly leached soils with

subsurface zone of clay accumulation and <35% base saturation

Composition of Soils

45%

5%

25%

25%

Mineral

Organic Matter

Air

Water

Mineral Particle Size Classifications

Sand0.05 – 2.0 mm

Clay<0.0002 mm

Silt0.002-0.05

mm

Surface Area

Sand Particle Clay Particles

Area of cube = l x w x 6

27 cubes with 6 sides1 cube with 6 sides

Soil Texture & Textural Class

• Texture is the proportion of sand, silt and clay

• Florida soils– Sand– Loamy land– Sandy loam

Photo credits: USDA-NRCS

Soil Structure

• Soil structure is the way soil particles are held together

• Called aggregates or peds

• Florida soils have weak or no structure

Figure Credit: University Corporation for Atmospheric Research

Granular Structure

Photo Credit: USDA-NRCS

Blocky Structure

Photo Credit: USDA-NRCS

Platy Structure

Photo Credit: USDA-NRCS

Prismatic Structure

Photo Credit: USDA-NRCS

Columnar Structure

Photo Credit: USDA-NRCS

Soil Color

Soil Color

Photo Credit: James Bonczek, UF-IFAS

Hue: dominant spectral color; Related to the wavelength of light.

Value: related to total amount of light reflected.

Chroma: measure of the strength of spectral color.

Soil Density

Particle Density• Mass solid particles

in a unit volume• Depends on

particle type (mineral vs. organic)

• Average = 2.65 g/cm3

Bulk Density• Mass soil in a unit

volume• Depends on pore

space• Bulk density range

– Sand = 1.2–1.8 g/cm3

– Clay = 1.0-1.6 g/cm3