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What is Soil?

What is Soil?. Conceptual Aspects: Habitat Micro-organisms Bacteria, Fungi – both good and bad Viruses Macro-organisms Worms, Arthropods, Detrivores and Predators Plants Small Mammals Birds. What is Soil?. Conceptual Aspects: Provider to plant life Rooting substrate

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What is Soil?

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  1. What is Soil? • Conceptual Aspects: • Habitat • Micro-organisms • Bacteria, Fungi – both good and bad • Viruses • Macro-organisms • Worms, Arthropods, Detrivores and Predators • Plants • Small Mammals • Birds

  2. What is Soil? • Conceptual Aspects: • Provider to plant life • Rooting substrate • Water holding and release • Nutrient supply and reserve • Heat sink and release • Soil gases • Symbionts • Bacterial and fungal • Insects

  3. What is Soil? • Physical Aspects: • Minerals (from rocks) • Sand • Silt • Clay and Colloids • Organic Matter • Plants and Roots • Detritus (decaying organic matter) • Animal waste (including microbes) • Pore Space • Air • Water

  4. What is Soil? • Carbon Sink • Water filter • Indicator of ecosystem health

  5. What is Soil? We need to keep all these things in mind in our management practices How does this change how we treat the soil?

  6. What is Soil? • Habitat • What happens when we disturb this habitat? • At micro and macro level? • What happens when we make additions to, or removals from, this habitat? • Carbon:Nitrogen ratio? • How do soil organisms and plants respond? • Nutrient loss or gain? • Providing for plant life • What are the short-term and long-term results? • Are we providing for the soil as well as the plants? • What is the difference?

  7. What is Soil? • As a habitat we need to treat soil like a living organism, which requires: • Food • Water • Air • Shelter • Cover crops • Mulch • Living • Dead • Snow • Tender loving care…

  8. Short commercial break Click me

  9. Physical Attributes of Soil • Mineral Components • Sand • Silt • Clay

  10. Physical Attributes of Soil • Sand • Largest soil mineral particles (.02 – 2 mm) • Formed greatly from physical processes • Spherical/erratic in shape • Sand = little rocks • Larger pore spaces • Good drainage • Does not hold a charge • Difficult to compact

  11. Physical Attributes of Soil • Silt • Size between sand and clay (.002 - .02 mm) • Usually physically formed out of sand • Hold and releases water well • Flat or round in shape • Holds very little charge • Feels soapy • Carried in moving water

  12. Physical Attributes of Soil • Clay • Smallest soil mineral particle (< .002 mm) • Holds water very well • Holds strong negative charge for mineral adsorption • Susceptible to compaction • Platy-/flat-shaped particles • Various lattice structures

  13. Physical Attributes of Soil • Clay • Understanding structure of clay is important for: • Compaction • Water holding • Cation adsorption • Soil cultivation • Clays are categorized by their layer structure • Relationship of Si-tetrahedral and Al-octahedral sheets • 2:1; 1:1; 4:1; 5:2

  14. Physical Attributes of Soil 2:1 Clay • Shrink and swell 1:1 Clay No change

  15. Physical Attributes of Soil • Shrink and Swell of Clay • Interlayer space expandswith increasing watercontent in soil • Space contracts as wateris removed • Clay can crack when it shrinks

  16. Physical Attributes of Soil • Mineral ratios determine soil texture

  17. Physical Attributes of Soil • Attributes of Different Soil Textures

  18. Physical Attributes of Soil • Why is Texture Important? • Water Infiltration • Water Storage • Fertility • Aeration • Trafficability • Soil texture knowledge is the key to developing an overall soil maintenance and improvement plan

  19. And now a short break… Click me

  20. Organic Matter • Soil organic materials are made up of: • Dead and decaying plants or animals • Animal manures • Microbial by products • Materials decomposed to different stages exist simultaneously • Manure and compost are common OM additions to soil

  21. Organic Matter • Organic matter’s role in soil: • Holds soil particles together; stabilizes soil • Reduces erosion risk • Increases soil’s water holding and transmitting ability • Stores and supplies nutrients to plants and microbes • Minimizes soil compaction • Carbon sink • Ameliorates the effect of environmental pollutants • Immobilizes them; reduces leaching • Usually 5-8% of soil; 30% or more in org. soils

  22. Organic Matter • Soil Organic Matter Characteristics • High Cation Exchange Capacity (CEC) • High in Carbon (C) • C:N ratio- indicator of Nitrogen (N) availability to plants • Nutrient concentration and ratios variable • Particle density: 900-1300 kg/m3 • Bulk density: 180-200 kg/m3 (peat) or 130 kg/m3 (forest) • Holds water better than mineral soils

  23. Organic Matter • Two Types of Organic Matter • Non-humic • Primary components from fresh animal and plant waste • Easily decomposed by microbes (when present) • Comprise 20-30% of Soil OM • Decompose to: • Carbohydrates (several types) • Amino Acids • Lipids • Lignin • Very resistant to decay • Other compounds

  24. Organic Matter • Two Types of Organic Matter • Humic • Biochemical decomposition of non-humic materials • Resistant to further decomposition • Accumulate in soil • Dark in colour – give soil dark characteristic • 60-80% of soil OM • 3 types: • Humins: larger particles; low number of carboxyl groups; inactive. • Humic acids: smaller than humins (approximately colloid-sized); more carboxyl groups than humins. • Fulvic acids: smallest humic substances; large number of carboxyl groups;  most active among humic substances.

  25. Organic Matter

  26. Organic Matter • Carboxyl and Hydroxyl Groups Slide 78

  27. Organic Matter Living Material Dies onto soil Non-Humic Humic This process is driven by biological decomposition – mostly from soil bacteria and fungi

  28. Organic Matter and Texture • What role does OM play in texture?

  29. And another break… Click me, damnit

  30. Soil Colloids • Soil Colloids • Microscopic soil particles (w/electron microscope) • Made up mostly of clays and organic materials • Very large surface area • Carry many exchange sites/charges • Mostly negative except in acid soils • Hold soil cations (positively charged) • Holds water to cations • Major contributor to soil nutrient holding capacity

  31. Soil Colloids • There might be a diagram here someday…

  32. And now another break Click Me

  33. Soil Formation Where does the mineral component come from? From the weathering of rocks. Rocks are made up of minerals

  34. Soil Formation • Primary Minerals  Sand and Silt • Formed at high T and P (at depth); anaerobic conditions • Physically and chemically formed • Secondary Minerals  Clay • Come from primary minerals • Formed at low T and P (at surface) with Oxygen present • Mostly chemically formed

  35. Soil Formation Weathering of Rocks Physical Chemical 1 Chemical 2 (note: base-forming cations) Chemical 3 Biological

  36. Five Soil Formation Factors Parent Material Climate Biota Topography Time

  37. Gleysol Soil Tiny little Video here

  38. Not another one… You know what to do

  39. Five Soil Formation Factors Parent Material • Residual • In situ; long periods of weathering • Cumulose • Due to plant life and anaerobic conditions • High water table • Peat and muck soils • Transported • Gravity - Colluvium • Wind - Eolian • Water - Alluvium • Ice - Glacial

  40. Five Soil Formation Factors • Climate • Temperature and rainfall are major factors • Affect intensity of weathering • Increased T and precipitation accelerate weathering • Biota • Plants influence organic matter • Arthropods and worms mix soil; add to OM • Small mammals also mix soil

  41. Five Soil Formation Factors • Topography • Slope influences soil development • Water infiltration rate • Surface runoff • Vegetation • Aspect • North and South slopes develop differently • Elevation • Climate changes with altitude

  42. Five Soil Formation Factors • Time • Often noted as most important soil formation factor • Our soils in Lower Mainland are relatively young • Since last ice age 10,000 years ago

  43. Five Soil Formation Factors Great Soil Formation Videos Here

  44. Soil Formation Processes • Additions • Losses • Transformations • Translocations

  45. Podzol Soil Video here

  46. Soil Horizons

  47. Soil Horizons • Organic (O) Horizon • High in organic residue from plant drop • A Horizon • Mineral component mixed with OM • Most fertile part of soil; location of much root activity • Exhibits Eluviation in soil solution • B Horizon • Subsoil • Exhibits Illuviation of clay, OM, oxides • C Horizon • Little influence by soil-forming processes

  48. Soil Horizons • Water (W) Horizon • Due to high water table • Found in Gleysols • Bedrock • Underlying consolidated material (solid rock) • LFH Horizons • Usually found in forest soils with high surface residue

  49. And now another break Click Me

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