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