Soil Biology and Organic Matter

1. Soil Biology and Organic Matter

2. Overview Soil is….. Minerals (the body) Organisms (the life) Vital to soil formation and development

3. Overview Soil is….. Minerals (the body) Organisms (the life) Vital to soil formation and development B. Teems with life 1 million bacterial in each cubic cm of topsoil 1 million earthworms per acre More Biomass beneath our feet than above

5. II. Plants (Macro and Micro) III. Animals (Macro and Micro)

6. II. Plants Microflora Why important?

7. II. Plants Microflora Why important? Most crucial life forms in soils (by far, the most abundant in number)

8. II. Plants Microflora Why important? Most crucial life forms in soils They generate their energy by breaking down complex organic tissue, thereby freeing vital nutrients for other plants. (Without these critters, these nutrients could be locked up indefinitely in complex organic compounds)

9. II. Plants Microflora Bacteria Single celled organisms; Greater number of organisms present than all others combined

10. II. Plants Microflora Bacteria Heterotrophic – derive energy by consuming complex organic debris (leaves, roots, stems, animal tissue)—releases ammonium for plants Requiring organic compounds of nitrogen and oxygen for nourishment Rhizobium Bacteria—fix Nitrogen from air (Legumes)

11. II. Plants Microflora Bacteria Heterotrophic – derive energy by consuming complex organic debris (leaves, roots, stems, animal tissue)—releases ammonium for plants Autotrophic – oxidize inorganic materials (sulfer, iron, carbon, ammonia).—releases nitrate and nitrite. Producing complex organic nutritive compounds from simple inorganic sources by photosynthesis

12. Microflora Actinomycetes (Act-tin-o-my-ce-tes) Single-celled organisms slightly larger than bacteria (fine, thread-like) Decompose complex organic materials in later stages in conversion to humus. Capable of producing antibiotics

13. Microflora Fungi Heterotrophic organisms capable of decomposing highly-resistant and complex organic compounds. Dominant flora when pH is less than 5 also…mycorrhizae fungus (Mi-cor-rizie) Extension of Plant roots

14. Old ham sandwich residue from Rock City fridge…… Microflora Algae Simplest green plant (needs sun and water) Blue-Green Algae most common Aids in adding organic matter

15. Microflora Factors Limiting Microflora Adequate supply of organic matter Temperature (Peat Bogs too cool, desert too hot) Moisture pH (6-8 optimal—Rizobium bacteria very sensitive) Oxygen Availability (most microflora aerobic)

16. Whereas microflora are affected by the ambient temperature and moisture, MACROFLORA tend to form in response to climate, parent material, and slope conditions.....

17. II. Plants B. Macroflora Grasses Shrubs Trees Function: Produce an array of complex organic materials (leaves, roots, stems, bark, wood, seeds)—affect soil chemistry, water retention, pH, organic matter, etc.

18. Function: Produce an array of complex organic materials (leaves, roots, stems, bark, wood, seeds)—affect soil chemistry, water retention, pH, organic matter, etc. Aid in rock weathering and soil formation Protect soil from erosion

22. III. Animals Microfauna Protozoa (amoebae, ciliates, flagellates) Single-celled organisms, need moisture (dormant when dry) “grazers, eat bacteria”—digestion aids organic decomposition.

23. III. Animals Microfauna Nematodes (“eel worms”) More complex than protozoa Dine on decomposing organic matter, living soil animals, living plant roots Destructive to crops

24. Breakfast Lunch Dinner III. Animals Macrofauna Ants and Earthworms Major mixers of soil Openings allow air and water movement

25. Taste like beef when slow cooked… III. Animals Macrofauna Springtails, Mites, Mammals, Humans “mix, mechanically alter add organics…”

26. IV. Soil Organic Matter Sources

27. IV. Soil Organic Matter Sources Predominantly from plant tissue Animals (minor source) Earthworms, centipedes, ants process and move plant residues

28. Great source of N, P, S Extensive decomposition Raw Organic Matter Humus IV. Soil Organic Matter B. Humus Formation 1. Term used for organic matter which has gone under extreme decomposition

29. IV. Soil Organic Matter B. Humus Formation 2. The ingredients of humus…

30. (Humus) (N Compound) Proteins—stores and slowly releases N in soil Also find concentrations of P, S, and high CEC Ability to absorb large volumes of water

31. Extensive decomposition Raw Organic Matter Humus IV. Soil Organic Matter B. Humus Formation 3. Carbon/Nitrogen relationships 800 Carbons 1 Nitrogen 10 Carbons 1 Nitrogen

33. Why not use sawdust or raw vegetation?

34. Why not use sawdust or raw vegetation? Raw vegetation invites large microbial population (they feed on C). Compete for N, and make it less available to higher plant communities.

35. Why not use sawdust or raw vegetation? Raw vegetation invites large microbial population. Compete for N, and make it less available to higher plant communities. Decomposition of organics (CO2 gas), and many critters die and decompose. Nitrogen remains. N fixed as protein in the microbes is now available to plants Resultant humus is highly enriched in N relative to the original raw vegetation, and has a greater surface area (higher CEC)

36. C:N = 400/1 So…should we add sawdust to a garden? C:N = 10/1

37. IV. Soil Organic Matter C. Amount and Distribution

38. Metric tons of organic matter per ha of 1 meter depth Amount and Distribution Influence of Climate and Vegetation

39. Wisconsin study of prairie vs. forest soils.

40. Practical Implications Clear and burn method of woodlands removes the majority of organics Cropping grasslands reincorporates organic matter into the system

43. IV. Soil Organic Matter Composting 1. (Compost)—organic material that has undergone significant biological decomposition

44. IV. Soil Organic Matter Composting (Compost)—organic material that has undergone significant biological decomposition Benefits: Reduces volume of organic wastes by 5-10x. Heat generated during decomposition kills many disease-causing microbes Lowers C:N Serves as excellent soil conditioner

45. 3. Methods

46. V. Soil Fertility Fertilizers

47. V. Soil Fertility Fertilizers

48. A. Fertilizers 5 – 10 – 5N P K

49. V. Soil FertilityA. FertilizersNitrogen Sources: ammonium, nitrate

50. V. Soil FertilityA. FertilizersNitrogen * darker, stronger leaves