Packet 2 Flashcards
Soil Composition
Soil is composed of mineral particles, organic matter, and living biomass.
Fine Earth Fraction
Mineral particle < 2 mm diameter.
Coarse Fragments
Mineral particle 2 > mm diameter.
Sand Particles
Mineral particle within the size range of 0.05 to 2 mm and visible without microscope.
Clay Particles
Mineral particle having effective diameters less than 0.002 mm.
Silicate Clays
Those containing crystalline, silicate (SiO4) minerals.
Oxide Clays
Those composed solely of oxides of iron or aluminum.
Amorphous Clays
Those composed of non-crystalline silicate minerals (i.e. like glass).
Soil Colloid
Extremely small mineral and organic particles, with large external and internal surface area.
Clay Flocculation
The process of soil aggregation.
Specific Surface Area
The surface area per unit mass of a collection of mineral soil particles (cm2 g-1).
Soil Texture
The relative proportion of sand, silt, and clay particles in a soil.
Soil Organic Matter
Non-living organic carbon in the soil and on the soil surface.
Biomass
Living organic carbon compounds in the soil.
Dissolved Organic Matter (DOM)
Compounds that are readily assimilated by soil organism. Can be readily leached through the soil.
Particulate Organic Matter
The primary carbon and energy source for heterotrophic soil organisms.
Humus
Colloidal, gel-like, chemically amorphous and poly-cyclic organic matter that is resistant to decomposition.
Black Carbon Organic Matter
Soil carbon from incomplete combustion of plant litter, such as charcoal left from fires.
Soil Aggregation
The association of soil particles together with organic matter, into larger sized units called aggregates or peds.
Soil Structure
When soil particles, mineral, and organic particles are assembled into aggregates.
Granular Structure
Roughly spherical, loosely packed granules.
Platy Structure
Relatively thin, horizontal aggregates found in surface and subsurface horizons.
Blocky Structure
Irregular but roughly cube like, found in well developed B horizons.
Prismatic Structure
Vertically oriented columns of different heights found in subsurface horizons and more commonly in arid and semi arid regions.
Single Grained Soil
A soil without aggregates or structure composed mostly of sand sized particles.
Massive Soil
Virtually all particles within a soil body are associated, with no separating cracks or voids.
Soil Total Porosity
The proportion of the total soil volume that is pore space.
Macropores
Large diameter pores (greater than 0.08 mm). present either as inter-aggregate spaces or as biospores.
Microspores
Small diameter pores (pore diameters less than 0.08 mm) formed between individual soil particles and component micro aggregates.
Inter-Aggregate Pores
Cracks and fissures in a soil profile.
Silt Particles
Mineral particle within the size range of 0.002 to 0.05 mm.
