3.4 The Soil System

1. 3.4 The Soil System “It’s more than just dirt” -Mr. Shefferly

2. The Soil System • Soil is a complex mixture of • Eroded rock • Mineral nutrients • Decaying organic matter • Water • Air • Billions of living organisms (DECOMPOSERS!!)

3. Soil Formation Over Time

4. Soil Formation • Very Slow Process • 1. Weathering of rock (mechanical) • 2. Deposition of sediments by erosion (mechanical) • 3. Decomposition of organic matter (chemical)

5. Soil System Food Web

6. Soil horizons (layers) Soil Layers O - (Organic) Freshly fallen leaves, twigs, animal waste, fungi A- Mixture of partially decomposed organic matter B- (Subsoil) Nutrients leached from A “Plant Roots” C- (Parent Material) largely inorganic material

7. Important Cycles (Nitrogen Cycle)

8. Nitrogen Cycle Terms • Nitrogen Fixation: Atmospheric N2 is made available to plants • Nitrification: Bacteria in soil convert ammonium to nitrates • Denitrification: Bacteria in soil nitrates to nitrogen gas • Assimilation: Living organisms take in the nitrogen to make proteins

9. Carbon Cycle

10. Soil Particles • Clay (very fine particles >0.002mm) • Silt (fine particles 0.05mm-0.002) • Sand (medium-sized particles 2mm-0.05mm) • Gravel (large coarse particles < 2mm) • Soil Texture is determined by the relative amounts of the different types and sizes of mineral particles Smallest Largest

11. Soil Texture Triangle

12. Soil Permeability • Rate at which air and water flow from upper layers of soil to lower layers of soil

14. Soil Erosion • Movement of soil, especially surface litter and topsoil • Two main agents of erosion • Wind • Flowing water • Occurs due to loss of plant in soil from: • Overgrazing • Deforestation • Irrigation

15. Global Soil Erosion Serious concern Some concern Stable or nonvegetative

16. Top Soil Erosion and Run Off from Farm

17. Gully Erosion In Bolivia

18. Wind removes topsoil

19. Erosion Continued • Erosion is harmful • 1. Leads to loss of soil fertility and ability to hold water • 2. Increases runoff of sediment that pollutes water and kills fish.

20. Desertification • Enlargement of deserts through human activities • Causes: Overgrazing, deforestation, irrigation, and erosion • Consequences: Worsening drought, famine, economic losses

21. Other Soil Issues Salinization Waterlogging Irrigation water contains small amounts of dissolved salts Evaporation and transpiration leave salts behind Salt builds up in soil Precipitation and irrigation water move downward Water table rises

22. Soil Issues Salinization Waterlogging

23. Toxification • An increase in soil acidity ( low pH = more acidic) • Caused by leaching of metals • Burning of plant material increases soil pH • Can be counteracted by using lime stone to raise the pH and reduce acidity • Large problem in the Ohio valley in the USA due to coal power plants

25. Soil Conservation • Reduce Erosion by… • Wind Reduction: Plant trees or bushes as windbreaks near edges of open fields • Improving irrigation: Prevent evaporation of water • Soil Conditioners : Add lime to raise the pH and prevent the soil from become too acidic • Soil Fertility: Rotate crops to prevent the depletion of nitrogen in the soil and add natural manure as fertilizer

26. Soil Conservation • Improve farming Methods: • Terracing • Contour planting • Strip cropping with cover crop • Alley cropping, agroforestry • Windbreaks or shelterbelts • Conservation-tillage farming • No-till • Minimum tillage

27. Terracing • Reduces soil erosion by controlling water runoff by holding water at each level

28. Contour Planting/ Strip Cropping • Each row acts as a small dam to help slow water runoff and reduce soil erosion

29. Alley Cropping • Crops are planted in alleys between trees/shrubs • Provides shade and helps to slow down the release of soil moisture

30. Windbreak in field • Barrier of trees planted around the edge of the crop • Prevents wind erosion, provides habitat for birds, and a • supply of fuel wood

31. A soil Lab Must!!Simpsons Diversity Index Review Use the Simpsons diversity index below D = ____________N (N-1)___________________ n1(n1−1) + n2(n2 −1) + n3(n3 −1) +…nk(nk −1) D = Diversity N = Total number of organisms of all species n = number of individuals of a particular species The higher the D value the more diverse the sample is!!!!!

32. Now You Try

33. Vermicomposting • Vermicomposting is the process of having redworms and other decomposer organisms process our organic waste and turn it into a great natural fertilizer (called worm castings). • Worm cast = worm poop • Creates Healthy Topsoil from waste that would end up in a landfill.