4.10 sg

Introduction

• Overview of the importance of soils and watersheds.

Page 2: Soils as Ecosystems

• Soil Definition: A renewable resource developing gradually through the weathering of rocks and organic material accumulation.

• Topsoil Accumulation: Slow process (~1 mm/year under ideal conditions).

• Management: Careful practices can renew soil indefinitely.

• Erosion Impact: Most practices deplete soil, with severe erosion rates reaching over 25 mm/year.

Page 3: Components of Soil

• Total Components: Six main components of soil:

  • Sand and gravel

  • Silts and clays

  • Dead organic material

  • Soil fauna (organisms) and flora (plants)

  • Water

  • Air

Page 4: Variations in Soil Composition

• Soil Types: Variations in the six components lead to diverse soil types.

• Soil Texture: Amounts of sand, silt, and clay are crucial characteristics.

• Loam Soils: Best for agriculture due to a balanced mixture.

• Brazilian Tropical Soils: Weathered red clays with low nutrients and water retention.

• Central US Black Soils: Nutrient-rich with good water retention properties.

Pages 5-6: Soil Texture

• Granule Sizes:

  • Sand: 0.05 - 2mm

  • Silt: 0.02 - 0.05mm

  • Clay: <0.02 mm

• Soil Texture Pyramid: Visual representation of soil texture proportions.

Page 7: Grassland vs. Tropical Rainforest Soil

• Comparison of soil characteristics between different ecosystems.

Page 8: Soil Fauna and Fertility

• Decomposition Process: Bacteria, algae, and fungi recycle nutrients from litter.

• Soil Diversity: One gram can contain hundreds of bacteria and vast fungal networks.

• Worms and Insects: Aid in processing organic material, aerating the soil.

• Mycorrhizal Symbiosis: Partnership between plant roots and fungi improving nutrient uptake.

Page 9: Soil Ecosystem Diversity

• Overview of various soil organisms contributing to soil health.

Pages 10-11: Soil Horizons

• Soil Layers: Horizontal layers called horizons make up a soil profile.

• Types of Horizons:

  • O Horizon: Organic layer with leaf litter and organisms

  • A Horizon: Surface soil with minerals and organic material

  • E Horizon: Leached of nutrients

  • B Horizon: Denser subsoil

  • C Horizon: Weathered rock fragments

Page 12: Soil Types and Composition

• Soil Variability: Different soils have unique layers influencing their productivity (e.g., temperate deciduous, forest, grassland).

Page 13: Importance of A Horizon

• Key Soil Types:

  • Mollisols: Thick organic-rich A-Horizon prevalent in farmland.

  • Alfisols: Thinner A-Horizon, less organic material, also significant for agriculture.

Page 14: Watersheds

• Water Behavior: After precipitation, water may evaporate, percolate to groundwater, or runoff into streams.

• Watershed Definition: Area of land catching and draining water into a specific body of water.

Pages 15-17: Watershed Examples

• Mapping: Various watersheds including Lake Erie and Ohio River with visual aids.

Page 18: Factors Affecting Watershed Quality

• Elevation: High points create watershed boundaries.

• Pollution Sources: Activities like road runoff, pesticide use, and sewage impact water quality downstream.

• Impermeable Surfaces: Increase runoff and pollution risk.

Page 19: Storm Drains and Wastewater Treatment

• Pollution Flow: Stormwater runoff is untreated, in contrast to treated wastewater from sewer systems.

• Sewage Treatment Processes: Overview of how wastewater is processed versus stormwater.