Exam 1
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Why is soil health and quality more important in the future?
-we depend on soils for food -demand increases as population increases -amount/quality of soil is decreasing because of soil degradation and urbanization -we may also depend on plant resources to provide us with materials as oil reserves deplete
What ecosystem services do soils perform?
Provisioning: providing goods such as water, food, lumber, raw materials such as clay for bricks, all ceramics (dishes, tile, etc.) Regulating: processes that purify water, decompose water, control pests, or modify atmospheric gases Supportive: assisting with nutrient cycling, seed dispersal, primary biomass production Cultural: scenic views, outdoor activities
How do soils support plant growth?
-provide physical support (hold roots) -air -water -temperature moderation -nutrients
How do soils regulate water supplies?
-help convert non-drinkable water into drinkable water -act as a water purifier–physical, chemical, and biological -physical filtration–filters out contaminants -chemical filtration– contaminants attach to soil particles -biological filtration–bacteria & fungi break down contaminants
How do soils recycle raw materials?
decompose dead plants, animals and other organisms, and make nutrients and other raw materials available to living organisms
How do soils modify the atmosphere?
• Direct source of pollutants (if soils aren’t managed correctly)-particulates (dusts)-gasses • Sink for air pollutions • Support for plant growth and microbial activity
What organisms live in soil?
worms, snails, beetles, fungi, gophers, bacteria, actinomycetes, protozoa, roundworms, centipedes, millipedes, pillbugs, flatworms
What do humans build with soil?
-houses -ceramics
Why is soil important in engineering?
soil types directly influence design of building and roads to ensure longevity and safety
“Big Picture” Goals soil provides
• Food • Nutrients • Fresh Water • Energy • Climate Change • Biodiversity • Recycling “wastes” • Global Perspective
What are the main soil physical properties?
• color • texture • texture classes • structure • aggregate • bulk density
How is color measured for soil?
-soils can be many colors depending on parent material and degree of weathering -some colors of dye and paint are still obtained from soil -measured using a Munsell Color Chart–contains chips of color that you match to your soil sample wet and dry
Why do we measure color of wet and dry soil?
soil colors can be different when they are wet vs when they are dry
What is soil texture?
-the relative % of sand, silt, and clay in a soil -whether soil particles are sand, silt, or clay depends on their size
What size are the following soil texture particles?
Sand: between 0.06-2mm (largest pore size, smallest pore space) Silt: between 0.003-0.05mm (moderate pore size and pore space) Clay: under 0.002mm (smaller pore size, largest pore space)
What does soil texture affect?
water holding capacity, aeration, drainage, compactability, leaching potential, ability to store plant
Water Holding Capacity
Sand: Low Silt: Medium to High Clay: High
Aeration
Sand: Good Silt: Medium Clay: Poor
Drainage
Sand: High Silt: Slow to Medium Clay: Very slow
Compactability
Sand: Low Silt: Medium Clay: High
Leaching Potential
Sand: High Silt: Medium Clay: Low
Store Plant
Sand: Low Silt: Medium Clay: High
Why does particle size affect so much?
• Pore Size and Area – affects water and air holding ability • Surface Area *all soils have a slight negative charge (anionic) *the greater the surface area, the greater the negative charge *influences the exchange of cations (many of which are plant nutrients) on the soil particle surface
Why is surface area an important factor in the qualities of soil?
the greater the surface area, the more microorganisms there are present