5 2 Soil Characteristics of Soil is part

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5. 2 Soil Characteristics of Soil is part of the regolith that supports the

5. 2 Soil Characteristics of Soil is part of the regolith that supports the growth of plants. • Regolith is the layer of rock and mineral fragments that covers most of Earth’s land surface.

5. 2 Soil Characteristics of Soil Composition • Soil has four major components: mineral

5. 2 Soil Characteristics of Soil Composition • Soil has four major components: mineral matter, or broken-down rock; humus, which is the decayed remains of organisms; water; and air.

Composition by Volume of Good-Quality Soil

Composition by Volume of Good-Quality Soil

5. 2 Soil Characteristics of Soil Texture • Texture refers to the proportions of

5. 2 Soil Characteristics of Soil Texture • Texture refers to the proportions of different particle sizes. - Sand (large size) - Silt - Clay (small size) • Loam (a mixture of all three sizes) is best suited for plant life.

5. 2 Soil Characteristics of Soil Texture (SAND) -Sand has less nutrients for plants

5. 2 Soil Characteristics of Soil Texture (SAND) -Sand has less nutrients for plants than smaller particles -Voids between sand particles promote free drainage and entry of air -Holds little water and prone to drought

5. 2 Soil Characteristics of Soil Texture (SILT) -Smaller particles – retains more water

5. 2 Soil Characteristics of Soil Texture (SILT) -Smaller particles – retains more water for plants and have slower drainage than sand. -Easily washed away by flowing water – highly erosive. -Holds more plant nutrients than sand.

5. 2 Soil Characteristics of Soil Texture (CLAY) -Pores spaces are very small and

5. 2 Soil Characteristics of Soil Texture (CLAY) -Pores spaces are very small and convoluted Movement of water and air very slow -Water holding capacity Tremendous capacity to adsorb water- not all available for plants. -Chemical adsorption is large

5. 2 Soil Characteristics of Soil Consistence -Loose: the soil breaks apart when held

5. 2 Soil Characteristics of Soil Consistence -Loose: the soil breaks apart when held -Friable: the soil breaks apart with a small amount of force -Firm: the soil breaks apart with a lot of pressure between two fingers

5. 2 Soil Characteristics of Soil Structure • Soil particles clump together to give

5. 2 Soil Characteristics of Soil Structure • Soil particles clump together to give a soil its structure.

Humus/Organic Matter • Organicmatterisismadeup upof: – Decomposing Plants – Decomposing. Such Plants as leaves

Humus/Organic Matter • Organicmatterisismadeup upof: – Decomposing Plants – Decomposing. Such Plants as leaves and flowers Such as leaves and flowers AND -Decomposing animals – Decomposing. Such animals as insects Such as insects • Organic Matter breaks down into nutrients • which Organic breaks into nutrients are. Matter used by plantsdown for growth. which are used by plants for growth.

5. 2 Soil Formation The most important factors in soil formation are parent material,

5. 2 Soil Formation The most important factors in soil formation are parent material, time, climate, and organisms. 1. Parent material • Residual soil—parent material is the bedrock • Transported soil—parent material has been carried from elsewhere and deposited

5. 2 Soil Formation 2. Time • Important in all geologic processes • The

5. 2 Soil Formation 2. Time • Important in all geologic processes • The longer a soil has been forming, the thicker it becomes. 3. Climate • Greatest effect on soil formation

5. 2 Soil Formation 4. Organisms • Organisms influence the soil's physical and chemical

5. 2 Soil Formation 4. Organisms • Organisms influence the soil's physical and chemical properties. • Furnish organic matter to soil

5. 2 Soil The Soil Profile Soil varies in composition, texture, structure, and color

5. 2 Soil The Soil Profile Soil varies in composition, texture, structure, and color at different depths. Soil horizons are zones or layers of soil. A soil profile is a vertical section through all the soil horizons. • The A horizon is commonly know as topsoil. • The B horizon is subsoil and contains clay particles washed out from the A horizon. • The C horizon is between B horizon and unaltered parent material.

Soil Profile

Soil Profile

A Soil Profile Showing Different Horizons

A Soil Profile Showing Different Horizons

5. 2 Soil Erosion Water erodes soil. Rates of Erosion • Human activities that

5. 2 Soil Erosion Water erodes soil. Rates of Erosion • Human activities that remove natural vegetation, such as farming, logging, and construction, have greatly accelerated erosion.

5. 2 Soil Erosion Controlling Erosion • • Planting rows of trees called windbreaks

5. 2 Soil Erosion Controlling Erosion • • Planting rows of trees called windbreaks Terracing hillsides Plowing along the contours of hills Rotating crops