Soil is a System. How do soils form? Mineralization: decomposition or oxidation of the chemical...
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Transcript of Soil is a System. How do soils form? Mineralization: decomposition or oxidation of the chemical...
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 AgeSoil is dynamic:Minerals, water, air, organic matter,
and organisms constantly changeSome are added, some lostSome move between layersSome 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) Climate- soil forms faster in warm, wet
climates Organisms- decompose matter, mix and
aerate soil, plants add organic matter Relief (landscape)- effects movement of soil,
and exposure to the elements Parent material- influences the properties of
the resulting soil Time-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