The foundation for life! Soil The foundation for life!

Soil Composition Mineral Particles (sand, silt, clay) Organic Matter 40% Organic Matter 10% Air 25% Water

Sand Loose granular material. Forms from the desinigration of rocks. Mostly silica (SiO2) Particles are smaller than gravel but coarser than silt. Large size (0.05-2 mm)

Silt Loose material Primarily powered rock. Particles are smaller than sand but coarser than clay. Medium size (0.002 to 0.05 mm)

Clay Dense material. Made of very small particles (less than 0.002 mm) Many different types. Compounds could consist of aluminum, silicon, oxygen, calcium, magnesium or potassium.

Organic material Comes from plants. Varies from location to location.

Pore Space Pockets of air and water between the solid materials that make up soil.

Ok so…. It is the combination of minerals, organic materials, and pore spaces that determine how well the soil can support plant life!

Sieves and Settling lab Sieves and settling are both measuring the same thing, the composition of the soil!

Sieves Only the small particles will pass through a sieve, the large particles will not. What is the difference between a particle and a ped?

Answer A ped is a natural cluster of soil whereas a particle is one piece of that cluster.

Why study soil? http://soil.gsfc.nasa.gov/pvg/1-1why.htm How much soil is there? http://soil.gsfc.nasa.gov/app_soil/hmsoil.htm

What makes soil? http://soil.gsfc.nasa.gov/inch/soiltime.htm It takes tens of thousands of years to make top soil. It’s NONRENEWABLE! http://soil.gsfc.nasa.gov/inch/soiltime.htm

A soils minerals comes from its parent material. (see samples) Weathering (physical, chemical & biological) It breaks down rocks into smaller particles. Erosion (dislodging of soil from one are to another) Occurs when the topsoil is exposed to wind or water that may wash/blow it away. Biological activity (deposition, decomposition and accumulation of organic matter) Decomposition breaks down complex organic molecules that plants can take up through their roots. Humus comes from partial decomposition. It’s dark, crumbly and holds moisture very well.

5 Factors that Influence Soil Formation Climate Soils form faster in warm wet climates. Organisms Earthworms and burrowing animals mix, aerate soil and add organic matter. Plants affect soil composition and structure. Topography Hills, valleys and exposure to sun, wind, water all influence how soil moves. Parent Material Creates the minerals. Time It takes a long time to make soil and the four factors above change over time.

Soil Layers pg. 239 Soil layers form over time. These horizontal layers are called soil horizons. O horizon (litter layer) organic matter A horizon (top soil) some organic matter mixed with minerals E horizon (leaching layer) where minerals and organic matter leach into the B horizon. B horizon (sub-soil) where minerals and organic matter accumulate. Often includes clay and chemicals such as iron. C horizon (hard bedrock) mostly parent material R horizon (pure parent material)

Organic Material Consists of decaying plant material and animal matter as well as bacteria, fungi, molds, ants, earthworms, spiders and other creatures. Prevents erosion Provides a nutrient reservoir Produces the soils color

Fertile soil Soil that contains the complete set of nutrients required by growing plants. A wide variety of ions must be available to a plant’s root system. Major nutrients from the soil are nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Major nutrients from water or air are carbon (C), hydrogen (H) and oxygen (O)

Cation exchange Plants gain their nutrients from a process called a cation exchange. Plants roots donate a hydrogen ion to the soil in exchange for a nutrient ion. Cation exchange is a useful measure of soil fertility. As soil pH becomes lower (more acidic), cation exchange diminishes leaving plants with less nutrients to absorb.

Nitrogen Stimulates above ground growth and produces the rich green color of a healthy plant. It also influences the quality of fruit and the fruit’s protein content. Can be added to the soil by planting legumes (peas, beans, alphalpha, etc.), adding organic matter or synthetic fertilizers.

Turn to pg. 28 for a lab Organic Components

Soil texture http://soil.gsfc.nasa.gov/pvg/texture1.htm