Introduction to Soil and Soil Resources 2001

1. Introduction to Soil and Soil Resources2001 Lecture 2

2. Tonight • Review lecture 1 • Update on lab manual • Soil Formation • Climate -Vegetation - Soil Patterns • Assignment 1

3. Lecture 1 Review What is Soil? Texture, Structure and Colour

4. Why is Soil Important? • Agriculture • Engineering • Home for flora and fauna • Life Support

5. What is Soil? Three phase system • Solid • Water • Gas

6. What is Soil? Combination of: • mineral material • organic matter • pore space

7. Soil Horizons • Mineral and Organic • Distinct layers of soil • Approximately parallel to the surface • Master horizons: A B C O L F H • Used to classify the soil

8. Pedosphere • Intersection of four spheres • Hydrosphere • Lithosphere • Biosphere • Atmosphere

9. What is the Pedosphere? The envelope of the Earth where • soils occur • soil forming processes are active

10. Soil texture • Percentage of sand, silt and clay • Size ranges of sand, silt and clay • Hand and laboratory methods • Texture triangle • Example: Clay Loam

11. Soil Texture • Affects aeration • Affects water holding capacity • Affects pore space

12. Soil Texture • Percent clay very important • Swelling and non swelling clays • Clay has a high surface area • Cation exchange capacity

13. Soil Structure • Physical property • Combination of primary soil particles into secondary particles, units or peds • Different shapes and sizes

14. Soil Structure • Grade, size, shape of the arrangements • Example: Strong, coarse, angular blocky • Structure affects the size and shape of pores • Aggregation very important

15. Soil Colour Tells us something about: • the air and water regimes in the soil • the amount of organic matter • the types of minerals that make up the soil

16. Soil Colour • Munsell Soil Colour Books • numeric and qualitative • hue • value • chroma • E.g.: Grayish brown (10YR 5/2 m)

17. Bulk density • Bulk density is • Db = mass of oven dry soil volume of soil • Unit is g cm-3 or Mg m -3 • example on page 61 of text book

18. Clarification of bulk density Slide 53 of lecture 1 may be confusing. Use slide 74 of lecture 1 and slide 17 of lecture 2 for a clearer definition of bulk density.

19. Particle density Particle density is • Dp = mass of soil particle volume of soil particle • assumed to be 2.65 Mg m-3 • example on page 59 of text book

20. Exam hints Know definitions. Know formulae for calculating bulk density and particle density. Remember that particle density is assumed to be 2.65 Mg m-3

21. Soil Formation Parent Materials

22. Types of rock • Magma: molten rock • Igneous : cold, solid magma • Sedimentary: materials deposited from suspension or precipitated from solution • Metamorphic: rocks changed by heat and pressure

23. The Rock Cycle (Reeves, 1998)

24. Regolith • Regolith • Unconsolidated debris from the breakdown of solid rock • May have formed from the rock it now lies on top of • Or been transported from somewhere else • Varies in thickness

25. Parent Material • Upper layers of regolith have been altered more than deeper layers • Deeper layers are most like the original regolith • This original regolith is the soil parent material

26. Moraine • An accumulation of earth, usually with stones, carried and deposited by a glacier • heterogeneous • unsorted and unstratified

27. Morainal parent material

28. Fluvial deposits • Deposited by flowing water • Includes glaciofluvial • Gravel, sand, and/or silts • Rounded grains, sorted and stratified

29. Fluvial parent material

30. Lacustrine deposits • Deposited in lakes • Stratified • Sorted • Absence of stones - usually

31. Lacustrine parent material

32. Eolian deposits • Transported and deposited by wind • Medium to fine sized sand • Medium to fine sized silt • or both sand and silt • Sorted

33. Eolian parent material

34. Colluvium • Moved by gravity • Heterogeneous mix of sizes • Unsorted • Unstratified • Rock fall

35. Colluvium parent material

36. Residual parent material • Formed from rock • Weathered in place • Not transported

37. Parent material in Canada • During Ice Ages, Canada was covered by ice. • The ice scraped off most of the surface and moved materials around • When the ice left, soil formation started all over again

38. The Laurentide Ice Sheet CoverGodfrey 1993

39. Glaciers and parent material • Glacial till (Also called till) • Ground moraine • End moraine • Recessional moraine • Lateral moraine

40. Glaciers and parent material • Kettle • Esker • Kame • Outwash plain • Braided stream • Drumlin

41. Formation and deposition of glacial materials R. C. Izaurralde & Pedosphere.com

42. Edmonton region during final stages of deglaciation (Godfrey, 1998)

43. Surface geology of the Edmonton region (Godfrey, 1998). Legend in textbook page 84

44. Weathering of Rocks and Minerals

45. Weathering of rocks and minerals • Rocks weather into minerals • Physical and chemical processes • Continues until primary particles formed • Primary particles can be further altered

46. Chemical weathering Accelerated by the presence of • water (and its dissolved solutes) • oxygen • organic and inorganic acids • Decomposition

47. Chemical weathering • converts primary minerals into secondary minerals • e.g. feldspars and micas into clays • dissolves essential elements out of minerals and makes them available to plants and organisms

48. Chemical processes • Carbonation • Hydration • Hydrolysis • Oxidation

49. Carbonation • A chemical weathering process in which dilute carbonic acid reacts with a mineral • Carbonic acid is derived from the solution in water of free atmospheric soil-air carbon dioxide

50. Carbonation • Rainwater dissolves CO2 producing carbonic acid. • This acid can dissolve limestone CO2 + H2O H2CO