SOIL HORIZONS Mrs. Wilson 9 th Grade Life Science

O-horizon Loose and partially decayed o rganic matter Leaf litter Animal droppings Surface of soil Includes plant roots

A-horizon Topsoil! Mineral horizon at or near the surface which has an accumulation of humus (organic matter) Very dark in color due to humus

E-horizon Eluvial horizon – exit! Mineral horizon which lacks color – usually made of sand Zone of leaching (losing) Loss of – Silicate clay – Iron – Aluminum

B-horizon Illuviation horizon Subsoil – usually brownish yellow in color Minerals move into this horizon and accumulate here – Iron  most common – Silicate clay – Aluminum

C-horizon Parent material Regolith Un-weathered Little or no sign of soil formation Lack of color Not affected by the soil forming processes above it

R-horizon Bedrock layer Very dense – few cracks and cannot be easily penetrated Examples: – Granite – Basalt – Limestone  in Florida! – Sandstone – Quartzite

Soil Textures Sand 2mm mm – Coarse, large – Water flows easy, high porosity Silt 0.002mm mm Clay < 0.002mm – Low porosity – Holds water easily

Soil Composition 50% solid particles – 45% minerals – 1-5% organic matter 50% pore space – 20-30% Water – 20-30% Air