  Explain how the resources soil provides help in supporting life; Explain how the resources soil provides help in supporting life;  Explain the contents of soil; Explain the contents of soil;  Describe the biological nature of soil; and Describe the biological nature of soil;  Describe four ways plants use soil. Describe four ways plants use soil. Objectives

  Soil provides many resources to life  They make it possible for plants and animals to grow  We will list five of them Soil Supports Life

  Oxygen  In the soil  Needed for root growth  Temperature  Soil absorbs heat from the sun  Soil radiates heat into the atmosphere  This cycle regulates the temperature so seeds can germinate and grow Soil Supports Life

  Water  Used by growing plants  Carbon  The base of all life forms  Most essential element to life  Nutrients  Minerals that are absorbed and used by the plant Soil Supports Life

  Soil is composed of four primary components  Mineral matter  Organic matter  Air  Water  In addition, there are numerous living organisms Contents of Soil

  Soil is 50/50 solid and porous  What is porous?  Solids  Mineral matter and organic matter Contents of Soil

  Solids  Mineral matter  45%of the soil  Broken down rocks  Sand, Silt, Clay  These three things determine water holding capacity and fertility of the soil Contents of Soil

  Solids  Organic Matter  5% of the soil  Mostly from leaves, roots and stems  Contributes to water holding capacity and fertility  Gives soil a dark color Contents of Soil

  Pore Spaces  Space occupied by air and water  Air  ≈25% of soil  Water  ≈25% of soil Contents of Soil

  Air  Constantly fluctuating  More water = less air  Less water = more air Contents of Soil

  Water  It can do two things with soil  Run off  Soak in Contents of Soil

  Terms to know  Infiltration  Water soaking into the soil  Percolation  Water moving downward through the soil  Permeable  Quality of soil when water can both infiltrate and percolate  Leaching  Movement of dissolved minerals and chemicals and salts downward with water Contents of Soil

  3 types of soil water  Gravitational water  Water pulled down by gravity  Causes leaching  Capillary water  Water held in pore spaces  May move sideways or up  Hygroscopic water  Water that forms a thin film around soil particles  Not available to plants Contents of Soil

  What life forms would you find in the soil?  Worms  Insects  Bacteria  Fungi  Other organisms Biology of Soil

  Bacteria and fungi have an important role in the soil.  They break down organic matter and release nutrients. Biology of Soil

  Earthworms, ants, crawfish, moles, and other organisms improve the soil tilth,  Tilth : the ease at which soil can be worked.  These organisms create openings in the soil as they tunnel.  This enhances drainage and improves air exchange. Biology of Soil

  What are they?  Anchorage  Water  Oxygen  Nutrients 4 ways plants use soil