Soil covers much of the land on Earth.Provides a substrate for plants to anchor their

roots.Provides homes for many animals.

Most soil types consist of three different layers/horizons. 

First layer (A horizon), consists of the dark, top part where organic (humus) material is present.The second layer (B horizon), is heavier and drier in texture than the A horizon.The third layer (C horizon), consists mostly of unaltered material that is poor in nutrient value. The bottom layer shown is solid parent material rock.

Over-cultivated poor soil

Rich fertile soil

Most roots are found in topsoil.

Topsoil is a mixture of mineral particles, living organisms, and humus.

Micro-organisms break down and recycle debris.

Acid soils have low pH.

Salt ions (Na+, Cl-) alter water potential.

Soil composition determines the degree of water and nutrient binding (to soil particles).

Does this lush, tropical forest look like it would have rich soil to grow in?

World Soil Types and Locations

The textural triangle classification of soil is made based on the relative proportions of silt, sand and clay. Follow any two component percentages to find the nominal name for the soil.

Soil Variability

oBedrock composition.

oWeathering and erosion-forces

oClimate over period of formation.

oTime over soil-formation forces.