1. From Bedrock to Soil

2.  Bellringer In your notebook answer the following questions: Has there always been soil on Earth? What makes soil valuable to humans?

3.   Describe the source of soil.  Explain how the different properties of soil affect plant growth.  Describe how various climates affect soil. Objectives

4.   Soil is a loose mixture of small mineral fragments, organic material, water, and air that can support the growth of vegetation.  Where do plants live?  Where do some insects live? Defining Soil

5.  Soil Formation  Soil is an important natural resource  It is found almost everywhere on Earth  Exactly what is it?

6.  Soil Formation  Soil forms in layers during the process of its development.  The parent rock is the solid bedrock from which weathered pieces of rock first break off.  The smallest pieces of weathered rock, along with living and dead organisms, remain in the very top layer.  Rainwater seeps through this top layer of materials, dissolves soluble minerals, and carries them into the lower layers of the soil.

7.   Residual Soil  Soil that remains above its Parent rock.  Transported Soil  Soil that is blown or washed away fomr its parent rock. Types of Soil

8.  Soil Layers  Topsoil  Animals, bacteria, fungi.  Humus  Subsoil  Smaller particles than parent material but not much life  Parent Material  Slightly weathered bedrock  Bedrock  Solid layer of rock

9.  Soil Layers

10.  Soil Profiles  What is a soil profile?  A vertical sequence of soil layers  A soil horizon is a distinct layer, or zone, within a soil profile.  There are three major soil horizons: A, B, A, B, and C.  Horizon A contains high concentrations of organic matter and humus.  Horizon B contains subsoil that are enriched with clay minerals.  Horizon C, below horizon B and directly above solid bedrock, contains weathered parent material.  The O horizon is organic material, that may or may not be present.

11.   Humus  The organic material formed in soil from the decayed remains of plants and animals.  Acidity  Soils can be acidic or basic. The pH scale is used to measure how acidic or basic a soil is.  Colors of plants flowers may be due to pH of soil  Leaching  The removal of substance that can be dissolved from rock and soil due to water passing through. Horizon Information

12.  Why does soil feel different?  Many different particles give soil its texture  Soil contains:  Sand  Silt  Clay

13.  Soil Texture

14.  Soil Textures  Particles of soil are classified according to size as being clay, silt, or sand, with clay being the smallest and sand being the largest.  The relative proportions of these particle sizes determine a soil’s texture.  The texture of a soil affects its capacity to retain moisture and therefore its ability to support plant growth.

15.  Soil Textures  To determine the texture of a soil sample, find its percent for sand, silt, and clay.  The texture of the soil will be where all three lines intersect.

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17.   Infiltration  How well can water move through the soil.  Leaching Soil Texture and Water

18.  Soil Fertility  A measure of how well a soil can support plant growth  Factors involved include:  Availability of nutrients/minerals  Precipitation  Topography  Acidity  Number of microorganisms present

19.   The topography of a region affects the thickness of developing soil.  Soils on slopes tend to be thin, coarse, and infertile.  Soils formed in lower areas, such as in valleys, are thick and fertile. Topography of Soil

20.  Soil Color  Factors that determine soil color include:  Climate  Soil’s composition  Topsoil-usually dark (rich in humus)  Red/yellow soils-caused by iron minerals oxidizing  Yellow soils are often poorly drained, associated with environmental problems  Gray/bluish soils-poorly drained, constantly wet, lacking in oxygen

21.  Soil Types  Polar Soils  Form at high latitudes and high elevations.  Located in Greenland, Canada, Antarctica.  No distinct horizons, very shallow soil.  Just below the soil the ground is permanently frozen-known as permafrost. Permafrost in Denali

22.  Soil Types  Temperate Soils  Lots of variation  Support forests, grasslands, prairies  Amount of rainfall determines what grows in this type of soil  Grasslands-lots of humus-soil is rich and fertile  Forests-soil is less deep/less fertile, containing clays and iron oxides (Eastern US)  Prairies-dry soil-lots of grasses and bushes

23.  Soil Types  Desert Soils  Very little precipitation  High levels of salts  Limited vegetation  Little or no organic matter  Very thin topsoil (A horizon)  Light colored and coarse soil

24.  Soil Types  Tropical Soils  High temperatures, heavy rainfall  Soil is intensely weathered, infertile  Source of ores (iron), but not great for growing plants

25.   In your notebook answer the following questions; 1.What is the difference between transported soil and residual soil? 2.What does each of the following mean: 1.Soil texture 2.Soil fertility 3.Soil structure Recap