Introduction to Soils

1. Introduction to Soils • Compliments of: • Elizabeth Sulzman OSU Soil Science • James Cassidy OSU Soil Science • Teresa Matteson Benton SWCD • Heath Keirstead Benton SWCD

2. Soil is … Absolutely crucial for life on Earth! www.pikeconservation.org/SoilEcosystem.htm

3. 5 functions of soil • Soil anchors and provides nutrients for plants. • Some animals live in soil; it is a habitat. • Soil recycles waste through decomposition. • Soil cleans and stores water. • Soil has engineering uses.

4. Active Factors Passive Factors The five factors of soil formation Soil = f(cl,o,r,p,t) • Climate • Organisms • Topography/relief • Parent Material • Time

5. Missoula Floods delivered parent material to Willamette Valley

6. Landscape positions

7. Soil Soil Soil Soil Soil Soil Soil Soil O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter O horizon: organic matter, plant and animal litter A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon A horizon: topmost mineral horizon, darker than B horizon B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation B horizon: mineral horizon: zone of accumulation C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life C horizon: weathering soil; little organic matter or life R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock R horizon: unweathered parent material; rock

8. Soil has four components • Minerals • Organic matter • Water • Air

9. The four components of soil:

10. Mineral component • Makes up less than 50% of a “soil” • Varies in chemical composition • Contains particles of several size ranges (small to really really small) • Depends on the underlying geology/bedrock

11. Organic matter • Small constituent by weight, but huge influence on soil properties • Made up of partially decomposed plant & animal residues + organic compounds synthesized by soil microbes O ni

12. Functions of Organic Matter 1. Stabilizes soil structure, making soil easily managed 2. Increases the amount of water a soil can hold (and availability of the water) 3. Major source of plant nutrients 4. Main food/energy for soil organisms

13. Soil Water • Held to varying degrees depending on amount of water and texture of soil • Not all soil water is available to plants

15. Soil Air 1. High spatial variability 2. High temporal variability 3. High moisture content (Rh 100%) 4. High CO2 content 5. Low O2 content

16. Soil Physical Properties • Color • Texture • Structure • Aggregate stability

17. Soil Color Moisture Mineralogy (calcite, hematite, manganese) Coatings on particles: O.M. darkens underlying colors Fe and Al oxides (red & yellow)

18. Texture • Proportions of sand, silt, and clay Determines water holding capacity, water availability, nutrient supply capacity… • Loam is a soil texture with optimal sand, silt and clay contents for growing plants. • Clay is a soil particle size and a soil texture.

19. % silt % clay % sand

20. Relative Size Comparison of Soil Particles (fine earth fraction) “Big”  smaller  really small Sand  silt  clay

21. Fine clay has ~10,000 times as much surface area as the same weight of medium grain sand! Sand Clay

22. Coarse textured soils larger pores Fine textured soils greater total pore space Sand Clay

23. + + + - - - NH4+ NH4+ - K+ + Ca++ - - - - - - - - Clay particle mostly negative charged surface - - - - - + - - - - Ca++ Fe++

24. Low Medium High Good Poor Medium High Slow Very slow Low Medium High Influence of Texture

25. Types of Soil Structure

26. Why Are Aggregates Important? • Increase porosity • Increase water infiltration, drainage, decrease runoff • Increase water holding capacity http://www.youtube.com/watch?v=9_ItEhCrLoQ

27. Effect of OM on aggregate stability

28. Effect of OM on aggregate stability

29. Compaction Pore spaces are where plants get air, water, and nutrients. Soil compaction decreases valuable pore space between soil particles. Adapted from Sulzman and Frey, 2003

30. Compaction Less Greater

31. Take home message • Clay soils have a higher water-holding capacity than sandy soils • Water in coarse textured soils is easier for plants to remove than in fine textured soils • Much of the water in high-clay soils is unavailable to plants, while most water in sandy soils is available

32. A cup of soil contains... Bacteria Fungi Protozoa Nematodes Arthropods Earthworms 200 billion 100,000 meters 20 million 100,000 50,000 <1 The immobile ones all primarily found in the rhizosphere, the zone of soil closest to plant roots

33. Bacteria

34. Nematodes Protozoa

35. Mites Springtails

36. Other invertebrates

37. Worms Voles! Ant Colony!

38. hyphae • Aggregates held together by: • Fungal hyphae • Bacterial “glues” • Organic matter clay sand silt bacteria

39. Amoebae Microfauna Ciliate • feed on bacteria and fungi • release plant nutrients – protozoa KEY for N Flagellate Nematode Nematode

40. Collembola (springtails) Fungus feeding mite Nematode feeding mite Mesofauna • feed on fungi, protozoa, nematodes, mites • important in regulating populations of everything smaller

41. Macrofauna • shred plant material • feed on bacteria and fungi associated with organic matter Photo by Suzanne Paisley

42. Earthworms • Important component of soil fauna (not in acid soils, not in very dry soils) • Pass as much as 30 tons/ha of soil through their bodies each year • Casts (poop) are higher in N, P, K, Ca, Mg, pH, and CEC than soil • Promote good soil structure and aeration

43. Earthworm casts vs. soil 38.8 849 13.8

44. via organic matter Nitrogen Fixation (bacteria) • Take N2 from atmosphere, convert to soil NH4+ • Nodules formed on roots • Examples include: • Rhizobia on legumes • Frankia on alder • N N NH4+

45. SOIL ORGANIC MATTER Dead tissues and wastes: DETRITUS Living Organisms:BIOMASS Non-living, non-tissue: HUMUS SOM: What it is

46. Large surface area means more charge so greater ability to hold water and nutrients Sand Clay

47. Hands-on FUN!!! Set up a soil column to see how soil purifies water.

48. Back to why we might care… …plants = food

49. Erosion: • A process that transforms soil into sediment • Natural (soils form over time in most settings) • Human-induced (e.g., over-grazing, forest harvest) • Tied with damage to plant communities • Wind vs. water (usually 2/3 by water)

50. Downward spiral of land degradation