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Compost 101Linn Benton Master Gardeners
Lecture notes Part 1
Teresa Matteson
January 26, 2011
Woody paths
Woody mulch
around
woody plants
Compost turf with high Nitrogen amendment
Cover
One year
(be careful with cotton seed meal)
Rate of decomposition depends on:
• Carbon to Nitrogen Ratio
• Air
• Water
• Size
• Time
C:N Ratio
• Ratio of carbon to nitrogen– Analogous to carbohydrates (carbon) and
protein (nitrogen) in our food
– High carbon materials are BROWN– High nitrogen materials are GREEN
C:N ratios• C always listed first,
grams C per gram N
25:1 or 25
• Lower C:N means
microbes need less N from soil
Critical Values of C:N
• C:N < 25:1, N release to plants
• C:N > 25:1, N taken from soil –microbes out compete higher plants every time
Organic material C/N
soil organic matter 10soil microbes 5-10alfalfa 13manure 20corn stover 57wheat straw 80sawdust 600
C:N ratio of different materials
Manure Comparison
Manure C:N Moisture
Chicken 10 37 - 69
Cattle 16 81
Horse 30 72 (seeds)
Sheep 16 69
Pig 14 80 (parasites)
C:N
Turn materials
Turn outside of pile to the center
so that all feedstocks
heat up
and smile!
AIR
Alternative to turning - Aeration pipes
AIR
Rule of thumb: 50% moisture
• Feels damp like a wrung-out sponge
• Should not drip when squeezed
WATER
COVER the pile to control moisture
WATER
Reduce sizeChopMowGrindChip
Increase
surface
areaSIZE
Minimum: 1 cubic yard - 3’ x 3’ x 3’
Maximum: <4 ft wide by <9 ft tall As long as you want
Pile size matters
SIZE
• It smells good, like the forest floor
• It is brown and crumbly
• The original materials cannot be identified
• It will pass through a ½” sieve toss overs back in the pile
When is your compost finished?4 criteria
TIME
•It is brown and crumbly
•The original materials cannot be identified
TIME
Make a ½ inch sieve that sits
on your wheelbarrow
Overs go back into the pile or
inoculate a new pile
Free-form pile
Build a hot pile
Build a hot pile
6 “ coarse brown
Build a hot pile
3” green
6” brown
Build a hot pile
6” brown
3” green
Add soil, amendments & MIX
Expensive
Holds moisture
Turning?