Soil .

What is soil?  Soil is the loose, weathered material on Earth’s surface where plants can grow

Why should you care about soil? One of Earth’s most valuable natural resources Everything that lives on land, including humans, depends directly or indirectly on soil

What is soil? One of the main ingredients of soil comes from bedrock Bedrock is the solid layer of rock beneath the soil Once exposed to the surface, bedrock gradually weathers into smaller and smaller particles which make up soil

What is it made of (what is its composition?) Soil is a mix of rock particles (weathered bedrock), minerals, decayed organic material, water and air Weathered bedrock = sand, silt and clay Humus = dark colored material that forms as plant and animal remains decay. It helps create spaces in soil for air and water. - Also contains nutrients including nitrogen, sulfur, phosphorus and potassium. Plants need nutrients in order to grow. They absorb nutrients from the soil.

What is Soil Fertility? A measure of how well the soil supports plant growth A measure of how nutrient-rich the soil is The more humus there is in the soil, the more fertile it is!

Value of Soil Fertile soil is valuable because there is a limited supply and takes a long time to form Soil value goes down when it loses its fertility and/or when topsoil is lost due to erosion Fertility loss – from exhaustion - George Washington Carver developed new crops and farming methods to help restore soil fertility to South (peanuts =legumes-add nitrogen that plants need)

Crop Rotation Farmer plants different crops in a field each year so same nutrients are used up every year After planting crops that use a lot of a certain nutrient, plants crops that put back that nutrient the next year

What is Soil Texture & Why is it Important? Describes the feel of the soil Depends on the size of the individual soil particles Classified by size Smallest particles to largest = Clay – Silt – Sand – Gravel (pg. 119)

What is Soil Texture & Why is it Important? Important for plant growth Soils that are mostly clay have a dense, heavy texture. The hold lots of water so plants could “drown” Sandy soils have a coarse texture. Water passes through quickly so plants could die from lack of water Loam (= parts clay, sand & silt) is best for most plants

How Does Soil Form? Forms as rock is broken down by weathering & mixes with other materials on surface. Constantly being formed where ever bedrock is exposed Gradually soil develops layers called horizons A Soil horizon is a layer of soil that differs in color and texture from the other layers

What is a soil profile? A soil profile refers to the layers of the soil These are known as Horizons O, A, B, C and R

What does the color of soil tell us? Generally, the darker the soil, the more nutrients it has. Darker soil usually means it has more humus in it.

How is Humus Formed? Decomposition=humus formation Plants contribute most of the organic remains that form humus. As plants shed leaves, they form a loose layer called litter - Organisms that live in soil (decomposers) break down dead plant remains, dead plant roots, other dead organisms and digest them with chemicals into humus

How is Humus Formed? Decomposers = fungi, bacteria, worms & other organisms Fungi are organisms like mold and mushrooms Very small animals such as mites and worms also decompose dead organic material and mix it with the soil

The soil must be mixed & aerated Earthworms do most of the work of mixing humus with the other parts of the soil Burrowing mammals (mice, moles, prairie dogs, gophers, etc.) also dig and break up hard, packed soil and mix in humus Earthworms and burrowing animals help to aerate, or mix air into the soil (pgs. 122-124)

Mixing the Soil These animals also add nitrogen to the soil when they produce waste They add organic material when they die and decay. Earthworms and burrowing animals also help to aerate, or mix air into the soil. Plant roots need the oxygen that this process adds

The O horizon is made of decaying plant and animal remains The O horizon is made of decaying plant and animal remains. It stands for organic matter. Bedrock is under the C Horizon. It is called the R Horizon. Textbook pg. 120

Litter It’s on top of the first layer of soil—the O horizon Contains grass, plants, and animals

Horizon A; Topsoil 1st layer of soil Darkest layer of soil (dark brown or black) Crumbly brown soil that contains humus, clay, other minerals, plant roots, small animals, water, and nutrients for plant growth The darker the soil, the more nutrients it contains

Horizon B; Subsoil 2nd layer of soil Lighter in color (reddish brown) Fewer nutrients and water Usually contains clay and other particles washed down A Horizon Little humus Limited plant growth

Horizon C 3rd layer of soil Lightest in color (gray) No nutrients, animals, or plant growth Contains partly weathered rock and sediment

R Horizon=Bedrock=Parent Material

In the order they form 1st = Horizon C 2nd = Horizon A 3rd =Horizon B It forms as bedrock weathers and rock breaks into small particles 2nd = Horizon A Forms as plants add organic material to the soil and plant roots weather pieces of rock 3rd =Horizon B Forms last as rainwater washes clay and minerals from the A horizon to the B horizon

Soil Types Scientists classify the different types of soil into major groups based on Climate Plants, and Soil composition

pH A measure of how acidic or alkaline (basic) a material is 7=neutral 0-7 = more acidic (lower number = more acidic) 7-14 = more basic (higher number = more basic) Different plants need different pH levels If too acidic then add lime If too basic then add sulfur

Moisture Loam is about 25% water, and is the best soil for growing most types of plants

So what is soil conservation and stewardship Stewardship = to take good care of something. Soil stewardship reminds us of our responsibility to care for our soil resources Soil conservation = management of soil to prevent its destruction

Humans can affect the quality of the soil Soil quality can affect human health Humans are responsible for monitoring and maintaining soil quality Avoiding pollution Chemicals Animal and human waste Soil Conservation

Con’t Loss of topsoil – water and wind erode exposed topsoil Plant cover helps protect it Dust Bowl – end of 1800’s , years of droughts, almost all Great Plains turned into farms or ranches, wind storms blew topsoil creating giant dust storms http://www.google.com/imgres?sa=X&rls=com.microsoft%3Aen-us%3AIE-Address&rlz=1I7TSNA_enUS455US455&biw=1366&bih=556&tbm=isch&tbnid=nVRy2kC_gH0uTM%3A&imgrefurl=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FDust_Bowl&docid=v600Qlnl4hoxEM&imgurl=http%3A%2F%2Fupload.w

3 Methods of Soil Conservation Contour Plowing Farmers plow fields along curves of slope to help slow runoff of extra rainfall Prevents extra rainfall from washing soil away

Conservation Plowing (Low-Till or No-Till Plowing) Farmers leave dead weeds and stalks in ground Try to disturb soil and plant cover as little as possible

Terraces Flat, step-like areas built on a hillside to prevent rainwater from running downhill

Wind Breaks Rows of trees between fields to “break” or reduce the force of winds.

Cover Crops or Vegetative Cover Planting crops all year long so fields are never left bare and the plants hold the soil in place.

Responsible Land Use Things that increase soil erosion: Logging, mining and construction Animal grazing Growing crops Recreation Off road vehicles