Soil Regolith layer of rock and mineral fragments

Soil �Regolith – layer of rock and mineral fragments produced by weathering �Soil – part of regolith that supports plant growth

Soil Composition �Mineral matter, humus (decayed, organic material), air, water

Soil Texture � Texture refers to % of particle sizes 1. Sand (large size) 2. Silt 3. Clay (small size) � Loam (a mixture of all three sizes) is best suited for plant life

Soil Texture

Soil Formation �The most important factors in soil formation are: � parent material � time � climate � organisms � slope

Soil Formation: Parent Material �Residual soil: parent material is the bedrock �Transported soil: parent material has been carried from elsewhere and deposited

Soil Formation: Time � • The longer a soil has been forming, the thicker it becomes

Soil Formation: Climate �Greatest affect on soil formation � hot/wet – thick/chemically weathered soil � cold/dry – thin/mechanically weathered soil

Soil Formation: Organisms �plants – main source of organic matter, acids from decay increase weathering �animals – burrow and mix materials (earthworms)

Soil Formation: Slope �steep – more erosion = thin/nonexistent soil �flat – little erosion = thick soils

Soil Profile �A Horizon – (topsoil) � mixture of mineral and organic matter, insects, fungi, microorganisms � B Horizon – (subsoil) � fine clay particles leached out of A horizon � C Horizon � partially weathered parent rock