Warm up: Tuesday, December 1st, 2015 What is arable land? What features might arable land have?

SOIL What’s the dirt on dirt?

“Life builds soil, soil builds life” Importance of Soil “Essentially, all life depends upon the soil…there can be no life without soil and no soil without life; they have evolved together.” Charles E. Kellogg, USDA Yearbook of Agriculture, 1938 “Life builds soil, soil builds life”

Soil Properties Composition Formation Porosity / Permeability Fertility- Nutrient Holding Capacity Texture

Composition – What is in soil? Air Water Humus –organic matter (animal & plant remains/feces) Inorganic Matter- sand, silt, clay, rocks, minerals Organisms

Soil Formation 1. Weathering breaks down rocks into smaller and smaller pieces Mechanical: physically breaking Chemical: chemically breaking

Weathering - Water rounds rocks

Weathering - Wind

Weathering - Burrowing Animals expose rocks

Chemical: breaking down rock through chemicals and chemical reactions Ex: rainfall, acid rain

Examples: wind, water (rivers, waves, waterfalls), gravity, glaciers 2. Erosion: movement of sediment and rock particles from one location to another. Examples: wind, water (rivers, waves, waterfalls), gravity, glaciers

3. Deposition: depositing materials in layers by dropping the sediments and particles in a new location. Wind or water lays down sediments Examples: gravel, beaches, sand bars

The Deltas of rivers- slow water flow where the river meets the ocean causes sediments to sink Aerial view of the Mississippi delta

Weathering BREAKS, Erosion TAKES, DEPOSITED in Layers like a WEDding cake

Soil Formation: Inorganic sediments- sand, silt, clay Living and decaying organisms (humus) “Life Builds Soil” Air and Water Time it takes 500 years for 1 inch of topsoil to form!

Remember: It can take b/w 200-1000 years for mature soil to form The Formation of Soil Remember: It can take b/w 200-1000 years for mature soil to form

So what do we do with the soil once it is formed??? Soil is used to support plant life – the base of the food chain and original food source for all other organisms Plants need… Sunlight (from the sun) Water (retrieved from the soil) Nutrients (retrieved from the soil)

WATER As discussed, water is also necessary for plants to grow. Soil plays a role in water availability to plants. Ability to provide water is determined by porosity and permeability.

In order to discuss this you must first understand the following: 1. Porosity: the volume of water/air the soil (spaces between the rock particles) can hold. The more porous a rock is, the more water it can hold. Water/pollution filled pore Gas/Air filled pore

Soil porosity doesn’t describe how well water or other liquids move through soils. Permeability addresses this concept. 2. Permeability: the ability for water/air to flow through the rock For example-gravel and sand are very permeable. Clay and granite are impermeable.

Soil Fertility A measure of the ability of soil to provide plants with : 1) sufficient amount of nutrients (measured by nutrient holding capacity) and 2) water (determined by porosity, permeability and percolation), and 3) a sturdy place for plants to anchor their roots

Nutrient Holding Capacity A soil’s ability to hold on to nutrients long enough for plants to absorb them N, P, Ca, Mg, Fe, Na, S pH balance of soil can also affect NHC (acidic vs. basic)

Soil Textures

Texture Matters! Soil Texture (% sand, silt, and clay) is the determining factor for many other soil properties: Permeability Porosity Fertility: clays have lots of nutrients compared to sand

SANDY SOIL Porosity – High – it can hold air but not water Permeability - High Nutrient Holding Capacity - Low

CLAY SOIL Porosity – low Permeability - low Nutrient Holding Capacity - High

LOAM SOIL Porosity – Medium Permeability - Medium Nutrient Holding Capacity - High

Soil Texture is based on the % of sand, silt, and clay

Soil Horizons

Soil Texture Practice: Use the percentages on the “texture triangle” to determine the types of soils A, B, C, and D

Why study soil in environmental science??? Soils are the foundation for terrestrial ecosystems. Understanding soils and the organisms that rely on it allows us to understand how human activity can affect those organisms For example…. Waste, Construction, Mining, Deforestation all affect soils