SOILS FORMATION, EROSION, AND CONSERVATION

1. SOILSFORMATION, EROSION, AND CONSERVATION Miller Chapter 10

2. I. Soil: Formation Erosion, and Conservation What is Soil? complex mixture of eroded rock, minerals, decaying organic matter, water, air, and living organisms. Ratios Differ among various soil types… Average Ratios: 45% Minerals 25% Water 25% Air 5% Humus

3. B. How Soil is Produced -Weathering of rock -Depositing of sediment -Decomposition of matter

4. C. Soil Zones (MATURE) -Soil is arranged into zones called… SOILHORIZONS -A cross-section of soil horizons is called… SOILPROFILE -Most mature soils have at least three of the possible horizons

5. LAYERS/HORIZONS O Horizon – Top layer/Surface Liter Layer -Characterized by debris and animal waste -Brown/black in color

6. A Horizon – Top Soil Layer -Consists of porous mixture of partially decomposed organic matter called… HUMUS Inorganic minerals -Most plant roots and organic matter found here.

7. B Horizon – Subsoil Layer and C Horizon – Parent Material Contain most of soil’s inorganic matter and varying mixtures of sand, silt,clay, and gravel C Horizon lies on BEDROCK

8. Soils: zones Immature soil O horizon Leaf litter A horizon Topsoil Regolith B horizon Subsoil Young soil C horizon Parent material Mature soil Bedrock

9. D. Soil Properties *Soils vary in content of … Clay Silt Sand Gravel -Relative amounts of different size and types determines SOIL TEXTURE -LOAMS –soils of equal mixture

10. 100%clay 0 80 20 Increasing percentage clay Increasing percentage silt 60 40 40 60 20 80 0 80 60 40 20 100%sand 100%silt Increasing percentage sand CLAY SILT SAND

12. 1. Infiltration: • Water moving through the soil layers

13. 2. Leaching: Soil components from upper layers being carried to lower layers

14. 3. Porosity: the measure of the volume of pores and distance of pores per volume of soil

15. 4. Permeability: the rate at which water and air can move through soil Water Water High permeability Low permeability

16. 5. Soil Structure: The way in which soil particles are organized and clumped together Texture NutrientInfiltration Water-Holding Aeration Tilth CapacityCapacity Clay Good Poor Good Poor Poor Silt Medium Medium Medium Medium Medium Sand Poor Good Poor Good Good Loam Medium Medium Medium Medium Medium

17. 6. Soil pH A measure of the acidity of the soil

18. II. Soil Erosion 1. The movement of soil components, especially surface litter and topsoil, from one place to another *Two main agents are… -Flowing water -Wind

19. 2. Types Of Water Erosion A. Sheet – Moving of water in wide flow B. Rill – Fast moving water that cuts small channels

20. Gully – Ditches and gulley’s are caused by fast moving water over steep, exposed soil

21. Global Soil Erosion Areas of serious concern Areas of some concern Stable or nonvegetative areas

22. 3. U.S. Soil Erosion -1/3 of the original top soil has been washed or blown away. -USDA states that soil is eroding 16x faster than it can form. -USDA estimated loss of $30 billion dollars from erosion in 1997

24. The Dust Bowl

26. 4. Other Problems Associated With Soil • Desertification- The productive potential of arid or semiarid land falls by 10% or more due to… • Human activities • Climate changes MUST REDUCE… • Overgrazing & deforestation

27. Moderate Severe Very Severe

28. B. Salinization- The accumulation of salts in soil Often associated with irrigation Effects: Stunts crop growth Lowers crop yields Kills plants

29. Severe Salinization

30. C. Water logging- • An over abundance of water within the soil Evaporation Evaporation Transpiration Waterlogging Less permeable clay layer

31. III. Soil Conservation 1. Reducing soil erosion and restoring soil fertility.

32. 2. Farming Techniques A. Conventional-tillage farming *Tilling in the fall B. Conservation-tillage farming 1. Minimum Tillage Farming 2. No Till Farming

33. 3. Terracing – Creation of broad, nearly level terraces that run across the contour of the lands -Mostly used on very steep gradients.

34. 4. Contour Farming- Plowing/planting crops in rows across the sloped contour of the land.

35. 5. Strip Cropping- Alternating rows of crops with low, ground hugging vegetation.

36. 6. Alley Cropping/Agroforestry- • several crops planted together in strips or alleys between trees or shrubs

37. 7. Windbreaks/Shelterbelts- Rows of trees to reduce wind erosion.

38. Conservation During Urban Development

39. IV. Soil Restoration -Fertility can be returned by using one of two major types of fertilizer… A. Organic B. Inorganic

40. -Animal manure Organic fertilizer -Green manure -Compost

41. Commercial inorganic fertilizer

43. Extreme Erosion