1. What is a soil pedon ? A pedon is a natural body of soil that is large enough to allow classification of the soil. Brady and Weil, 2002 Horizons classification

2. Soil scientists have developed detailed terminology for describing soil pedons. We will learn many of these terms later in the semester. Today we will think about “pedons personified”. http://www.britannica.com/ebi/art-19380

3. Parts of a soil body skin skeleton stomach connective tissues respiratory system circulatory system

4. Sand and silt are the bones of the soil skeleton http://www.ecogrowth.com.au/soil.htm Soil skeletons

5. Clay and humus are the soil skin and connective tissues humus clay minerals http://www.ccma.csic.es/dpts/suelos/Brady and Weil (2002)

6. Why is the soil skin important ?  Adsorption of water films  Adsorption of organic and inorganic chemicals  Ion exchange  Catalysis of chemical reactions  Habitat for bacteria

7. What is humus ???? While it is unlikely that any 2 humus molecules are identical… the diverse products of “humification” have many common characteristics:  Extreme chemical complexity  Resistance to further decomposition  High specific surface and negative charge  Dark color

8. What is texture ??

9. Textural triangle 12 textural classes http://www.oneplan.org/Images/soilMst/SoilTriangle.gif

10. Textural triangle 12 textural classes http://www.oneplan.org/Images/soilMst/SoilTriangle.gif

11. Textural triangle 12 textural classes http://www.oneplan.org/Images/soilMst/SoilTriangle.gif

12. Textural triangle 12 textural classes http://www.oneplan.org/Images/soilMst/SoilTriangle.gif How much sand, silt and clay is represented by this location ?

13. Why do the textural class zones have such strange assymetrical shapes ? Soils within each zone behave similiarly

14. Textural triangle 12 textural classes http://www.oneplan.org/Images/soilMst/SoilTriangle.gif What do these textural classes have in common?

15. They are all “loamy” ! ! Loam soils have favorable physical properties for agriculture

16. http://www.grdc.com.au/growers/gc/gc48/conference1.htm The soil fabric Granular crumb structure Compacted soil How are the primary particles arranged in real soils ?

17. Granular crumb structure

18. 25 years of corn with moldboard tillage 20 years of bluegrass sod followed by 5 years of corn with moldboard tillage

19. 25 yrs of conventional corn 20 yrs of bluegrass, then 5 yrs conventional corn Water stable aggregates After adding water

20. 20 years of similar tillage but different types of organic inputs manure cover crops crop residues How do these soils differ ?? Rodale Institute Farming Systems Trial

21. Contrasting stands of corn in the NC tillage systems experiment No-till Fall plow/ spring disk

22. Plasticity vs. Friability Friable soils crumble easily when subjected to mechanical stress. Tillage requires less draft !

23. Angular blocky structure enhances drainage and root growth below the plow layer Ray Weil

24. Soil is habitat !! The Furrow

25. The Soil Stomach Bacteria Fungi Algae Protozoa Nematodes Microarthropods Enchytraeids Earthworms Ants, termites, spiders Mollusks Others: rodents, snakes, voles, amphibians, etc. Body size increasing Microflora Mesofauna Megafauna Microfauna Macrofauna

26. BACTERIA SSS A bacillus spirilla cocci filamentous

27. FUNGI

28. The fence post principle Schriefer (2000)

29. The fence post principle Schriefer (2000)

30. The soil pore network serves as a respiratory and circulatory system http://www.mtm.kuleuven.ac.be/Research/NDT/IDO_SHerman_final.ppt

31. Texture affects the pore network

32. No-till soilTilled soil Tillage affects the pore network (Young and Ritz, 2000) white zones are pores plow pan

33. Long term no-till Intensive tillage Ontario Ministry of Ag and Food plow pan network of biopores

34. NO Brady and Weil (2002) Traffic affects the pore network

35. Crusts impede seedling emergence, infiltration of water and gas exchange http://www.oznet.ksu.edu/soybeanscene/may24.htm

36. high residue high infiltration

37. Field Capacity Permanent wilting point Plant available water Pore diameter 10-30 μm 0.2 μm Drainage pores Hygroscopic water Adapted from Buol (2000) Most available Soil circulatory system

39. Ontario Ministry of Ag and Food Why do crops on tiled-drained land tend to be more drought resistant ?

40. What’s in the soil soup ?? Adapted from Brady and Weil (2002) Ca +2 NO 3 - Ca +2 K+K+ K+K+ Mg +2 Ca +2 Mg +2 Ca +2 Mg +2 Ca +2 NO 3 - SO 4 -2 NO 3 - H 2 PO 4 - DOM Cu +3 Fe +3 Zn +2 soil water

41. Plants take up mostly inorganic forms of nutrients when inorganic forms of nutrients are readily available In some natural ecosystems (e.g., tundra), organic forms of nutrients are very important

42. What are these guys up to ?