Soil & Agriculture Chapter 9

 sinesstechnology/ _inperson maas06.html sinesstechnology/ _inperson maas06.html sinesstechnology/ _inperson maas06.html  Local business building methane digesters in Enumclaw  ionworld/ _duststorm23.html ionworld/ _duststorm23.html ionworld/ _duststorm23.html  Current dust storms in texas

The Soil Profile PEnvironmentalScience/course%20file s/multimedia/lesson17/animations/2c_ soil_formation.html PEnvironmentalScience/course%20file s/multimedia/lesson17/animations/2c_ soil_formation.html

Influences on Soil Formation  Parent material - glacial or wind blown  Climate - precipitation & temperature  Topography - steepness of slopes  Organisms - plants and animals that live and die in an area  Time - how long has the soil been there

Formation of Soil  Weathering – break down of soil  Erosion – movement of soil  Deposition – arrival of eroded soil

Physical Weathering  Breaks up into smaller pieces without changing chemical make-up  Freezing/Thawing, Collisions/Abrasions

The “Old Man of the Mountain” in New Hampshire Pre 2003 Post 2003

Chemical Weathering  Changes the chemical make-up of the rock to a different substance  Dissolution/Oxidation

Soil Profile is made up of horizons  O horizon – organic matter  A horizon – Topsoil/humus, most nutrients found, where roots located  E horizon – minerals leach out  B horizon – Subsoil, leached minerals accumulate  C horizon – Weathered parent material  R horizon – Bed rock

 su.edu/resources/soil _classification_genes is/soil_formation/soil _transform.swf su.edu/resources/soil _classification_genes is/soil_formation/soil _transform.swf su.edu/resources/soil _classification_genes is/soil_formation/soil _transform.swf  Animation on how soil forms

Soil Profile Eluviation /Zone of Leaching – water percolates down the soil, transporting materials. Happens in Horizons A & E Illuviation/Zone of Accumulation – where transported materials are deposited. Happens in Horizon B. O A B C E

Chemical vs. Physical Soil Tests  What would be the difference between a physical & chemical soil test?  Examples of chemical tests?  Nitrogen  Phosphorus  pH  We did these already with the ecocolumns

PHYSICAL SOIL TESTS

Particle Size  Biggest  Sand  Middle  Silt  Very Fine  Clay  Fine particles have higher cohesion  Loam  About equal parts of each  Sandy Loam  All 3 parts, but more sand

Dry Percolation Rate  Rate of water flow in dry soil  Smaller particle size = Greater surface area = Slower flow  Compare sand and clay  What type of soil might have water pooling on top of it?  Rate  Cubic cm of water per surface area per second (cm 3 /cm 2 /sec)

Permeability  Rate at which liquids flow through pores (drainage rate)  Flows easier through soil with large pores  Unit  mL/min

Porosity  Measure of space in the soil (squishiness)  Measure of the volume of water that can be held by a volume of soil  Ex. Digging down and finding damp soil, when the top is dry

Physical Soil Tests  Difference between percolation rate & permeability?  What type of soil particle would have the lowest rates for both? Why?  What type of soil particle would have the highest porosity? Why?  Why loamy soil the most ideal for farming?

WHY SHOULD YOU CARE ABOUT SOIL?

Shift from Traditional to Industrial Agriculture  How did this shift degrade soil?  In the early 1930’s several years of drought – led to the Dust Bowl  cfm?guidAssetId=1A5D7C1C-BB3D-4F76- A DF302AFBD&blnFromSearch=1 2 segments cfm?guidAssetId=1A5D7C1C-BB3D-4F76- A DF302AFBD&blnFromSearch=1 cfm?guidAssetId=1A5D7C1C-BB3D-4F76- A DF302AFBD&blnFromSearch=1

As a result of the Dust Bowl … Many people migrated further westMany people migrated further west Soil Conservation Act of 1935 & Natural Resources Conservation ServiceSoil Conservation Act of 1935 & Natural Resources Conservation Service Assess land’s resources, problems, & opportunities for conservationAssess land’s resources, problems, & opportunities for conservation Use science to make plansUse science to make plans Work with land owners to ensure conservation and continued economic useWork with land owners to ensure conservation and continued economic use

Soil Conditions Today  n.com/id/ /# n.com/id/ /# n.com/id/ /#

Current soil conservation  In the U.S. about 1/3 of the topsoil has been lost (198 million acres ruined)  90% of the land currently farmed doesn’t use soil conservation practices  Erosion is worse now than during the Dust Bowl in the 1930’s

System that is causing soil degradation? Amount of arable land? System – relationships among components that interact with & influence on another Positive or Negative Feedback Loop?

FARMING METHODS TO PROTECT SOIL

Crop Rotation  Plant a different crop in a field each year  One year usually is soybeans  Excellent at fixing nitrogen

Contour Plowing  Using the natural “contours,” curves of the land when plowing or planting  Helps prevent erosion from run-off

Terracing  Used on steep land  Platforms, boxes used to prevent erosion from run-off  Also gives water time to absorb

Shelterbelts or Windbreaks  Rows of trees or large plants that slow wind

Reduced Tillage/No Till Agriculture  Land isn’t tilled or minimally tilled  Previous years nutrients left behind to decompose

HOW SOIL DEGRADATION OCCURS

Desertification  Creation of desert, due to land deterioration caused by human activities  Often in arid or semiarid lands  Caused by:  Poor farming practices  Overgrazing  Deforestation  Overuse of water sources

Salinization  Occur in arid to semiarid areas  Evaporation > Precipitation  Build up of salts in surface soil

 What stops farmers from using these methods?  Lack of education  Can require upfront investment  Short term vs. long term profit

Other impacts on soil quality…  Use of inorganic/organic fertilizers  Overgrazing  Deforestation

Careers in Soil   Soil scientist: Soil scientist:  EO08ck&feature=related EO08ck&feature=related EO08ck&feature=related