Transcript Humus and Composting

A respiration process:
Organic matter
+ O2
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Energy for decomposers
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CO2 + H2O
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Nutrients, that were in the original organic
tissue, for plants
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Carbon, nitrogen, etc. for the decomposers
 HUMUS !
Ultimate decay product
of decomposition
“Amorphous, colloidal
mixture of complex
organic substances,
not identifiable as
tissue”.
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< 0.00001 mm in diameter
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Nutrients and water attach to surface area of
soil particles
 Smaller the particle, the greater the surface area
per unit volume
 Sand 0.05 – 2.0 mm
 Silt 0.05 – 0.002
 Clay <0.002
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Humus <0.00001 mm
▪ Tremendous ability to hold water and nutrients
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A supply of N, P, S for plants
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Holds water
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Provides structure
 Glue that allows soil to have spaces
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Prevents erosion
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Carbon : organic compounds
 stores energy
 Cycled back and forth from
atmosphere to biosphere
▪ photosynthesis and respiration
▪
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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 15-100 years
Passive (stable) 500-5000
CARBON OUT
CARBON IN
Manure
SOIL
Respiration
1. Fossil Fuel Burning
2. Net Loss of Soil Organic Carbon
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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
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Restore the humus portion!!!!
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Organic farming
Non-chemical no-till
Manage trees and forests
Keep green manure
Diversify crops
Compost
Mulch
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Speeding up decomposition by making
breeding grounds for decomposers
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Making soil
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Need to pay attention to amounts of carbon
relative to nitrogen in the organic waste you
throw into the compost.
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This is the C:N ratio
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C:N ratio
 High C:N means not much nitrogen (“BROWN”)
▪ Slow to decompose
Sawdust, newspaper, wood chips, straw, timothy hay; shredded
cardboard; unshredded leaves
 Low C:N means plenty of nitrogen (“GREEN”)
▪ Fast to decompose
 Rotted manure ; household compost, cover crops, weeds, kitchen
waste, grass clippings, young alfalfa hay, beer mash from brewery,
shredded leaves, ash from fires, hair, orchard litter, spoiled hay, bird
cage cleanings
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1. Originally, about twice as much BROWN as
GREEN stuff layered together with thin layers
of soil or compost between.
3-4 ‘ high
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2. Turn / Aerate
 prevent “smelly” anaerobic decomposers
 Provides oxygen for aerobic decomposers
 How often?
▪ When cools down (approx. every 2 weeks)
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3. Keep adding green
 When you turn the compost, the “layer cake” is
messed up. That’s fine.
 Keep adding green with a little soil/compost
and a little straw or something brown every
now and then.
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4. Pile should be about 1 cubic yard to have
critical mass needed for heating.
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5. Keep moist but not sopping wet.
Decomposers prefer some moisture but too
much renders the pile anaerobic.
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Initially there is a mesophilic phase (1-2 weeks)
 Organisms decomposing the easy waste (sugars)
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After approx.1- 2 weeks, the temperature of the
pile will heat up to thermophilic phase (140 –
160 °F)
▪ Heat due to respiration
▪ Feeding frenzy by decomposers, now tackling more difficult
materials and producing humus.
▪ Decomposers are getting C,N,P,K from compost to build their own
bodies; when they have acquired all they need, temps drop.
▪ Heat will kill weed seeds and pathogens.
▪ Lasts 1 – 2 weeks; when cools down, need to turn again to
provide oxygen for further respiration
1. improves “texture” (Binds sandy soil; loosens clayey soil)
2. strengthens structure (Fungal mycelia, worms, humus)
3. aerates soil due to good structure
4. erosion control ( Water seeps slowly through composted soil)
5. Holds water (100 lbs humus holds 195 lbs water)
6. Neutralizes toxins:(Forms complexes with substances like heavy
metals, making them unavailable for plant uptake)
7. Doles out nutrients slowly (excess nutrients don’t get leached out and
end up in water)
8. Compost can stretch the growing season by darkening the soil
9. STOP THE WASTE! Why waste all of that energy that plants
carefully collected from the sun and put it in a landfill???
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Any residue suspected of being treated with
pesticide
Grease, oil: inhibit decomposition
Meat or animal products (eggshells okay):
attracts pests
Cat litter or feces
Difficult to decompose materials: big wood,
shells, corn cobs