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GES 175, Science of Soils Lecture 6, Soil Biology.

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Presentation on theme: "GES 175, Science of Soils Lecture 6, Soil Biology."— Presentation transcript:

1 GES 175, Science of Soils Lecture 6, Soil Biology

2 The Little Guys

3 CO 2 O2O2 Detritus (Plant Debris) Fungi Earthworms Bacteria Soil Humus energy

4 Soil Bacteria Ruehr’s Rule: “The bugs get it first”.

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7 CH 2 O  CO 2 NH 4 +  NO 3 - Fe 2+  Fe 3+ H 2 S  SO 4 2- NO 3 -  NH 4 + Fe 3+  Fe 2+ SO 4 2-  H 2 S O2  H2OO2  H2O Energy Yield Electron Donor (food) Electron Acceptor E donor - E acceptor Energy

8 CH 2 O CO 2 O2O2 H2OH2O NO 3 - CH 2 O CO 2 N2N2 Fe(OH) 3 CH 2 O CO 2 Fe 2+ CH 2 O CO 2 SO 4 2- H2SH2S Energy Yields Donor Acceptor 700 400 100 Eh (mV)*Condition oxic suboxic anoxic *pH 7

9 Aerobic Organisms Food Source Organic carbon* Ammonium Ion (NH 4 + ) Ferrous Iron (Fe 2+ ) Hydrogen Sulfide (H 2 S) Electron Acceptor Molecular Oxygen (O 2 )

10 CH 2 O  CO 2 NH 4 +  NO 3 - Fe 2+  Fe 3+ H 2 S  SO 4 2- O2  H2OO2  H2O Energy Yield Electron Donor (food) Electron Acceptor Energy -400 -36 KJ/mol

11 Anaerobic Organisms Food Source Organic carbon* Ammonium Ion (NH 4 + ) Ferrous Iron (Fe 2+ ) Hydrogen Sulfide (H 2 S) Electron Acceptor Nitrate (NO 3 - ) Manganese (Mn 4+ ) Ferric Iron (Fe 3+ ) Sulfate (SO 4 2- )

12 CH 2 O  CO 2 NO 3 -  NH 4 + Fe 3+  Fe 2+ SO 4 2-  H 2 S O2  H2OO2  H2O Energy Yield Electron Donor (food) Electron Acceptor Energy -400 -36 KJ/mol

13 Microorganism-Plant Relationships

14 legumes Bacterial-Plant Symbiosis

15 - bacteria require plant for growth; plant gains ‘free’ source of available N Nitrogen Fixation * Symbiotic relation between bacteria and plants: -e.g., legumes + Rhizobium * Grasses-Azospirillum/Azobactor

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18 N-Fixation: Frankia Frankia Nodules on Alder - actinomycetes - associates with desert shrubs (e.g., Ceanothus) and various tree species (e.g., alder)

19 Fungi-Plant Interaction Mycorrhizae (root fungus) - extension of root system - fungus enhances nutrient and water intake - plants provide carbon source Nearly 90% of native plants have mycorrhizae association

20 Ectomycorrhyzae - association at exterior of root - develop on evergreen trees and shrubs

21 Mycorrhizae - Associations occur in root interior between cells - Develop on deciduous trees, annual and herbaceous plants Endomycorrhizae

22 Organic Matter Degradation (Carbon Cycling)

23 CO 2 Detritus (Plant Debris) FungiEarthworms Bacteria Soil Humus Organic Matter Biomass Humin (insoluble) Humic Acid (insoluble in acid) Fulvic Acid (soluble) degradation (nonliving, nontissue decay products) (identifiable dead tissue) (living organisms)

24 Pools of Soil Organic Matter

25 Soil Humus Organic Matter Degradation: Nutrient Cycling Biomass Detritus (Plant Debris) Nutrient Release Nutrient Incorporation

26 -reactive functional groups: -carboxyl, hydroxyl, phenolic Soil Organic Matter: Humus - High cation (anion) exchange capacity - High water holding capacity - Promotes soil aggregation

27 To continue…

28 Fertilizer Effects on Soil Organic Matter

29 Effect of manure on organic matter


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