1. SOIL ALIVE!
Land, then, is not merely soil; it is a foundation of energy flowing through a circuit of soils, plants and animals”. Aldo Leopold

2. “ Soil is the hidden, secret friend, which is the root domain of lively darkness and silence” Francis Hole
Soil by parts:
5% organic, 50% space, 45% mineral

3. 5% Organic
Living, dead, decomposing, decomposed

4. Organic portion composed of:5%
10%
85%

5. “organic” What is special about Organic compounds? They have ENERGY
Food chain passes energy along through photosynthesis and respiration

6. Green plants can directly use sun
Photosynthesis:
CO2 + H2O + solar energy C6H12O6 + O2
organic !

7. Rest of us are only indirectly solar-powered
Respiration:
C6H12O6 + O2 ENERGY + CO2 + H2O

8. Food Chain Concept Energy is passed from one
trophic level to the next.

10. What is an organic compound?
Bank of energy

11. Organic materials in soil:
More living biomass below ground than above!
Beneath 1 acre: equivalent to 12 horses
1 cubic meter of soil:
50,000 earthworms
50,000 insects and mites
12 million roundworms
1 pea-size bit of soil:
30,000 protozoa
50,000 algae
400,000 fungi
Billions of bacteria

12. fungi
Springtails
earthworms
Beetles
bacteria
mites
actinomycetes:
geosmin, antibiotics
nematodes
pseudoscorpion

13. Springtails Arthropods Spring or hop Detrivores 100,000 / m3 topsoil
Invertebrates with external skeleton
Spring or hop
Detrivores
100,000 / m3 topsoil

14. Beetles Arthropods; order Coleoptera 400,000 species (40% of all
known insect species)
Some omnivores, some
eat plants, fungi, some
are carnivores
Larvae (grubs)

15. pseudoscorpons Arachnid Carnivorous: eat larvae, ants, mites, flies
Joint-legged invertebrate
Carnivorous: eat larvae, ants, mites, flies

16. earthworms Annelids Some 2700 different types 3 categories:
Epigeic (leaf litter/compost dwelling )
Endogeic (topsoil or subsoil dwelling )
Anecic (deep burrow drillers)

17. Giant Benefits to soil Move air in and out of soil
Castings are rich in available nutrients
Produce 10 lbs / yr

18. Nematodes Roundworms Occupy many positions in soil food web
> 28,000 species
Most microscopic
Can be predatory or parasitic

20. Mites
arachnids

21. Extracted from one ft2 of top two inches
of forest litter and soil

22. Bacteria Abundant; most important decomposers Adaptable Specialized:
Non-photosynthetic
Photosynthetic
Oxidize ammonium, nitrite, iron, manganese
Oxidize sulfur
Nitrogen-fixing
Aerobic, anaerobic

23. bacteria
1 ton / acre

24. Bacteria and fungal hyphae

25. Fungi Break down OM, esp important where bacteria are less active
branched hyphae form mycelium: bears spores
attack any organic residue

27. Symbiotic ; infecting plant roots, formed by some fungi
Mycorrhizae: s
Symbiotic ; infecting plant roots, formed by some fungi
normal feature of root systems, esp. trees
increase nutrient availability in return for energy supply
plants native to an area have well-developed relationship with mycorrhizal fungi

29. Higher fungi have basidium : club-shaped structure , bearing fruiting body
toadstools, mushrooms, puffballs, bracket fungi

30. Actinomycetes Filamentous morphology varies adaptable to drought
neutral pH
usually aerobic heterotrophs
break down wide range of organic compounds

31. Decomposition
A respiration process:
Organic matter
+ O2

32. Products of decomposition…
Energy for decomposers
CO2 + H2O
Nutrients, that were in the original organic tissue, for plants
Carbon, nitrogen, etc. for the decomposers
HUMUS !

33. What is HUMUS?
Ultimate decay product of decomposition “Amorphous, colloidal mixture of complex organic substances, not identifiable as tissue”.

34. Colloidal in size: tiny!
< mm in diameter
Nutrients and water attach to surface area of soil particles
Smaller the particle, the greater the surface area per unit volume

35. Humus <0.00001 mm Sand 0.05 – 2.0 mm Silt 0.05 – 0.002
Clay <0.002
Humus < mm
Tremendous ability to hold water and nutrients

36. Functions of humus: A supply of N, P, S for plants Holds water
Provides structure
Glue that allows soil to have spaces
Prevents erosion

37. About structure…

38. Humus sequesters carbon!!!
Carbon : organic compounds
stores energy
Cycled back and forth from atmosphere to biosphere
photosynthesis and respiration

39. sequestration
Take carbon from atmosphere and move it into long-lived soil pools where it is securely stored for very, very long time
SOIL CARBON POOLS:
Fast 1-2 yrs
Slow years
Passive (stable)

40. CARBON OUT CARBON IN SOIL Plant residues Harvesting plants Respiration
Manure
Compost
Erosion

41. Two Main Causes of Increased CO2 Emissions:
1. Fossil Fuel Burning
2. Net Loss of Soil Organic Carbon
Soil Carbon Sequestration:
Potential to offset fossil fuel emissions by 0.4 to 1.2 gigatons of carbon per year, 5-15% of global fossil-fuel emissions

42. How? Restore the humus portion!!!! Organic farming
Non-chemical no-till
Manage trees and forests
Keep green manure
Diversify crops
Compost
Mulch

43. COMPOSTING
Speeding up decomposition by making breeding grounds for decomposers

44. Composting is creating habitat for decomposers to make humus!
Making soil
Need to pay attention to amounts of carbon relative to nitrogen in the organic waste you throw into the compost.
This is the C:N ratio

45. Amount of N is more critical than amount of C :
Carbon usually makes up 45 – 55% of dry weight of tissue
Nitrogen can vary from 0.5% - 6.0%
For a residue with:
50% carbon and 0.5% N, C:N ratio would be ?
100:1 (wide/high C:N)
50% carbon and 3.0% N, C:N ratio would be ?
16:1 (narrow/low C:N)

46. Carbon : Nitrogen ratio
C:N ratio
High C:N means not much nitrogen (“BROWN”)
Slow to decompose
Sawdust 600:1 ; straw 80:1 ; newspaper 120:1
Low C:N means plenty of nitrogen (“GREEN”)
Fast to decompose
Rotted manure 20:1 ; household compost 15:1
Break-point between high and low = 25:1
WHY?

47. …because microbes have needs too!
Soil microbes’ cells need 8C: 1N
Only 1/3 of C from compost is taken into the cells
Therefore they need compost with 24 : 1

48. If C:N is > 24:1 Intense competition for N
Microbes will build their bodies first, then give up N for plants; N deficiency

49. If C:N < 24:1
Plenty of N to be released for plants

50. 1 compost
4”green”
1 compost
8 “brown”