Soil Properties

Flashcards about soil properties

Soil Texture

The particle size distribution of a soil.

Texture

A soil's coarseness or fineness based on particle size distribution.

Stones

Particles larger than sand.

Importance of Soil Texture

Influences infiltration rates, cation exchange capacity, and workability.

Soil surface area

Important for retention of water, cations, anions, and nutrients.

Coarse-textured soils

Rapid water movement due to larger pores and little surface area.

Fine textured soils

Water can be retained due to large surface areas.

Sand

Fraction between 2000 – 63 µm and feels gritty.

Silt

Fraction between 63 – 4 µm and feels smooth like powder.

Clay

Particles (<4 µm; feels sticky), mostly secondary minerals.

Loam

Ideal soil for agriculture consisting of silt.

Sand characteristics

Well drained and aerated but vulnerable to drought.

Silt (loam) characteristics

Moisture is retained, easy root penetration, and easy to plough.

Clay characteristics

High nutrient and organic matter but difficult to plough.

Importance of Soil moisture

Vertical movement of water, development of horizons, and provides solvent for plant nutrients.

Soil moisture expression

Water proportional to Rain – (Evap + Trans + Drainage).

Adhesion water

A thin film of water normally spreads out over a dry soil particle when wetted.

Adhesion water characteristics

Water so strongly adsorbed that it cannot be moved by plant roots.

Cohesion water

Water molecules further away from the soil particle surface attract each other through cohesive forces due to hydrogen bonding

Cohesion water

Water retained in soils due to cohesive forces.

Gravitational water

Soil water that exists in macro-pores and is normally removed by drainage because of the force of gravity.

Field capacity

Maximum water retained against gravity, after free water has drained.

Hygroscopic water

Always present but unavailable for plant use – sticks strongly to particles of soil.

Gravitational water availability

Unavailable for plant roots; lost by gravity

Capillary water availability

Available for plant roots; lost by evapotranspiration

Hygroscopic water availability

Water adsorbed to soil particles

Macro nutrients

Required in large quantities such as phosphorus(P), calcium (Ca), magnesium(Mg), nitrogen(N), potassium(K), sulfur(S)

Micro nutrients

Required in small quantities such as boron(B), chlorine(Cl), copper(Cu), iron(Fe), manganese(Mn), molybdenum(Mo), zinc(Zn)

Natural vegetation

The natural vegetation of an area is in equilibrium with the supply of available nutrients

Humification

Organic matter becomes humus