Compost!
Jody Slagle, P.E.
Austin Water
Compost And It’s Importance
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The Soil Ecosystem
Organic Matter
Mulch, Compost and Humus
Compost – the basics
Why Worry About Soil?
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It’s the basis for crop production
It cycles most nutrients and is a huge C sink
It can be degraded or lost easily
For every pound of food we produce we
lose 22 pounds of soil
• It takes hundreds to thousands of years to
make an inch of soil
Soil Formation
The Microbial Living Room
SURFACE AREA IN 2 TABLESPOONS
OF SOIL EQUALS ONE CITY BLOCK
An Acre Beneath Our Feet
Organism
Numbers
Bacteria
Trillions
2,600
Fungi
Trillions
2,600
Actinomycetes
Billions
1,300
Insects/Athropods
thousands
830
Earthworms
thousands
445
Protozoa
billions
90
Algae
billions
90
Nematodes
millions
45
Total
Elaine Ingham, Soil Foodweb.com
Pounds
7,800
It’s Alive!!!!!
Soil Ecosystem
Ecosystem
Cycles
•N cycle - protein
• C cycle – plant material
• Water cycle
• Short circuiting cycles
• Recycling?
Organic Matter
The life of the soil
The Nitrogen Cycle
Why Carbon and Nitrogen?
• Carbon: carbohydrates from photosynthesis
• Nitrogen: amino acids, proteins, nucleic
acids
Collembola - Springtails
Nematode trapping fungi
Mulch
Compost
and Humus
Mulch
• Organic or inorganic covering over the soil
• Can be compost, bark, leaves, gravel,
plastic, etc
Benefits of Mulch
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Moderate soil temperature
Improve water penetration
Reduce soil compaction
Retain soil moisture
Reduce weed problems
Can be used to keep produce off the ground
Compost
• Decomposition of organic materials with
cycling of nutrients
• Concentrate the processes used in the soil
Benefits of Compost
• Recycles organic materials
• Builds soil structure and improves aeration
and moisture properties
• Cycles and releases nutrients for plant use
• Foundation for life in the soil
Humus
• Dark colored semi-stable organic material
• Composed of material resistant to
decomposition such as lignin, fats
Compost Methods
Or Large Scale
At Hornsby Bend
Composting
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Air
Moisture
Food source
The decomposers
Physical Decomposers
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Mites
Beetles
Millipedes
Sow bugs (Pill bugs)
Springtails
Worms
Collembola - Springtails
Microbiology
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Protozoa
Fungi
Actinomycetes
Bacteria
Number and Biomass of Soil Organisms
Number/
Number/
Biomass
Organisms
yd3
oz
(Lbs/Acre-6”)
Bacteria
Trillions
Millions +
400 – 4.000
Actinomycetes
Trillions
Billions
Billions
Billions
Millions
30 – 300
Millions
Thousands +
Thousands
Thousands
Tens +
400 – 4.000
500 – 5,000
20 - 500
15 – 150
10 – 100
100 – 1,000
Fungi
Algae
Protozoa
Nematodes
Earthworms
4% organic matter is 80,000 lbs per acre
Decrease to 1% means loss of 60,000 lbs per acre
Planet Bacteria
• We live in a world of bacteria
• Bacteria cycle most of our oxygen and cycle
most of our nutrients
• Bacteria do most of the work in composting
• Bacteria reproduce by dividing
• One gram of bacteria can become a pound
in three hours, a mass greater than the Earth
in one and a half days if it had enough
resources
Bacteria Farmers
• Composting is a process of managing the
conditions for bacteria to break down
organic materials
• There are many different types of bacteria
in compost
• They like moist warm conditions
“Greens and Browns”
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All organisms need Carbon and Nitrogen
Bacteria use C and N in a ratio of 30:1
High nitrogen: green grass, food, manure
High carbon content:
– Dry leaves, wood, dry hay, sawdust
Mix High Carbon with High Nitrogen
Moisture and Oxygen
• Bacteria and other living things need water
• About 50% water, like a squeezed out
sponge
• Want air to be able to circulate so pile can
breathe
• Smaller particles versus air circulation
What Are My Goals?
• What materials do I want/need to compost?
• Do I need to get my pile hot? (Over 130
degrees kills weed seeds and diseases)
Slow Composting
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Layers
Ensure adequate moisture
Leaves can form a “roof”
Mix of nutrients
Fast Composting
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Right mix of materials
Moisture
Air flow
Turn and mix
Hot Composting
• Bacteria produce the heat
• When weed seeds or plant diseases are a
concern
• At least three feet on each side to hold heat
• More careful about moisture, recipe and
mixing
Dillo Dirt Composting
• Goal to minimize pathogens
• At least 15 days above 55C or 130F
• At least five complete turns
What Can I Compost?
• Theoretically anything organic (it was alive)
• Avoid fecal material of humans or pets
Organic Materials
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Food – fruits, vegetables, grains
Cotton, wool, silk, burlap, leather, feathers
Untreated or unpainted lumber
Paper, cardboard
Animal waste like manure – probably not in
your backyard
• Landscape trimmings – watch for diseases
Assess the Materials
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How much?
What materials with what properties?
What are my goals?
Where will I use the compost?
Decide on pile or bin
• Bins help retain moisture and can exclude
animals
• Large bins or piles may be required for
large amounts of material but can be hard to
manage
• At least three feet on each side to retain
moisture, heat
Mix Materials
Water
• Compost should feel like a damp sponge
Turn Every Week or Two
Questions?