Soil is a System

How do soils form? Mineralization: decomposition or oxidation of the chemical compounds in organic matter into plant-accessible forms. Soil Profiles Soil is made of layers called horizons

Soil Profiles: based on physical and chemical characteristics  O Horizon (humus)- partially decomposed leaf matter = high organic content  A Horizon (topsoil) – most fertile layer & most biological activity  B Horizon (subsoil) – w/ clay, Fe, Al, & other water soluble compounds leached from O & A. Deep plant roots penetrate this layer  C Horizon (parent rock) – contains large unweathered rocks

Soil Profile:  Like a biography, each profile tells a story about the life of the soil.  Soil is formed from parent material:  Weathered bedrock  Smaller materials carried by water, wind or glaciers  Sun, water, wind, ice, and living creatures help transform parent material into soil.

Soil Profiles by Biome:  Grasslands: most well developed soils, rich in organic matter – thick O and A horizons  Temperate deciduous forest: thick layer of leaf litter to enrich the soil however, high rainfall means leaching of nutrients  Boreal forest: short growing season, cold winters, acidic soil = poor farmland  Tropical rain forest: due to high temp. & rainfall, decomposition occurs very fast.  Deserts: low rainfall, low organic matter

Soil Changes With Age  Soil is dynamic:  Minerals, water, air, organic matter, and organisms constantly change  Some are added, some lost  Some move between layers  Some are transformed

What makes soil, SOIL?  Soil has texture  Soil has structure:  Texture & structure = soil behavior  Granular soils w/ a loamy texture make the best farmland  Soil has color, which tells of the mineral content:  Iron: orange-brown to yellowish-brown  Organic matter: dark brown or black  Soil has pH: influences plant growth

5 Factors that Influence Soil Formation: (CLORPT)  Cl imate- soil forms faster in warm, wet climates  O rganisms- decompose matter, mix and aerate soil, plants add organic matter  R elief (landscape)- effects movement of soil, and exposure to the elements  P arent material- influences the properties of the resulting soil  T ime-soil forms over decades, centuries or millennia & changes w/ above 4 factors

NO SOIL, NO LIFE……WHY?  Soil is the thin, outermost layer of the Earth’s crust  It performs critical functions in any terrestial ecosystem  Most of our food comes directly or indirectly from plants nourished by soil*  Soils provide habitats for organisms*  Soils filter our drinking water naturally*  Soils process & recycle nutrients*  *Ecosystem services

Soil Erosion is a global problem  Protecting the soil from erosion helps reduce air-borne dust  Soil Organic Carbon (SOC) can be sequestered by using no-till systems  Prevention:  Contour farming  Crop rotation  Intercropping  Terracing  Shelterblets  Reduced tillage

Desertification:  Describes the process of land becoming less suitable for cultivation – more desert like.  Causes:  Intensive farming techniques  High amounts of irrigation and inorganic fertilizers  Overgrazing  Effects:  Loss of micronutrients & organic content  Inability to grow crops on arable land

Remediation of desertification:  Organic fertilizers  Crop rotation  Phytoremediation  Desalinization