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Goshen Exchange

SustainabilityLesson 2 of 7

Composting

Breakout About 8 min readNew to you

What you’ll learn

  • The recipe for a hot pile: carbon to nitrogen, moisture and size
  • The 131°F rule that makes compost safe for food gardens
  • What never goes in a home pile, and why
  • Leaf mold, sheet and trench composting
  • How much finished compost your beds really need

The short version

  1. Mix to about 30 parts carbon to 1 part nitrogen. That means browns (leaves, straw) with greens (food scraps, fresh grass, manure). Keep the pile as damp as a wrung-out sponge and at least 3 × 3 × 3 ft.

  2. The safety line is 131°F for 3 days throughout the pile, or 15 days with 5 turnings in a turned row. Most home piles don't reach it evenly, so treat them as not fully pathogen- or weed-seed-free.

  3. Never use dog, cat, pig or human manure on food gardens.

  4. Test outside hay, straw, manure and compost with a pea or bean pot before using it. Some weed killers survive animals and composting and twist tomato and bean leaves for years.

  5. Leaf mold takes 1–2 years and makes excellent mulch. Don't overdo compost: about ½–1 in a year in established beds, plus a soil test every few years.

Hot composting (fast, kills more weed seeds)

The recipe

FactorTarget
Carbon: nitrogenAbout 30:1 by weight (25–35:1; USDA organic requires 25–40:1 to start)
MoistureWrung-out sponge. A hard squeeze gives a drop or two
SizeAt least 3 × 3 × 3 ft (1 cubic yard); 3–4 ft per side is ideal
PiecesChopped to under about 2 in
AirTurn when the center cools (about every 5–10 days)

Browns and greens

Carbon-to-nitrogen ratio of common materials, by weight:

Greens (nitrogen-rich)C:NBrowns (carbon-rich)C:N
Poultry manure (fresh)~10:1Maple leaves~30:1
Food scraps12–20:1Oak leaves~60:1
Fresh grass clippings12–25:1Straw40–100:1
Coffee grounds~20:1Paper150–200:1
Cattle manure~20:1Cardboard, newspaper400–560:1
Horse manure (with bedding)20–60:1Wood chips, sawdust100–750:1

Sources disagree on "browns to greens" by volume, giving 2:1, 1:2 or equal parts. Start near equal volumes and adjust:

  • Ammonia smell means too much green; add browns.

  • Cool and slow means too much brown, too dry or too small; add greens or water, or make it bigger.

  • Rotten-egg smell means too wet and airless; turn it and add dry browns.

Step by step

  1. Pick a spot: level, well-drained, near a water source. Shade it in hot, dry regions.

  2. Build at least 3 × 3 × 3 ft in one go if you can, mixing or layering browns and greens and wetting each layer.

  3. Check the heat with a long compost thermometer. A working pile heats within days.

  4. Turn it when the center starts cooling, moving outside material to the middle, because the edges stay cooler.

  5. If it passes about 160°F, turn it. Hotter than that kills the helpful microbes.

  6. Active composting: about 3–8 weeks of hot work.

  7. Cure: let it sit 4–12 weeks before use, longer for seed-starting.

Is it done?

  • Look and smell: dark, crumbly, earthy-smelling, with nothing recognizable.

  • Size: about half the starting volume.

  • Heat: within about 10°F of the air temperature after turning.

  • Seed test: plant radish or cress seeds in compost, or water them with compost tea, beside a plain-water control. Poor sprouting means it needs more curing.

Cold (slow) composting

Pile materials as you get them and let time do the work. It takes 3–9 months, up to a year or two. It's easy, but it won't kill weed seeds or pathogens, so keep weedy material and manure out unless you'll hot-compost them.

Bins

  • Wire hoops and pallet bins are cheap.

  • Three-bin systems let you build, cook and cure batches side by side.

  • Tumblers turn easily; rotate daily to several times a week.

  • Plastic bins freeze sooner in cold climates.

  • Open piles work if you have room.

Keep these out of home compost

  • Food that draws pests: meat, fish, bones, dairy, oils.

  • Dog, cat and human waste.

  • Diseased plants and seeding weeds, unless your pile truly gets hot.

  • Black walnut, coal or charcoal ash, treated wood, glossy paper.

Diagram coming soonCompost pile cross-section
Figure 1. A working pile: hot core, cooler shell.
Diagram coming soonC:N seesaw
Figure 2. Balance browns and greens near 30 to 1.
Sources: Cornell University, NC State Extension and 8 more

The safety rules

Diagram coming soonTemperature gauge
Figure 3. What the compost thermometer is telling you.
Diagram coming soonPea bioassay
Figure 4. The pea test for weed-killer residue.
Sources: USDA National Organic Program, Published research and 12 more

Leaf mold, sheet and trench composting

Leaf mold

Pile or bag fall leaves and keep them damp. Fungi break them down slowly over 1–2 years, faster if shredded.

  • Uses: mulch and soil conditioner; 2-year-old leaf mold makes good seed-sowing mix.

  • Not a fertilizer. Leaves are high in carbon (C:N 35–85:1). Don't till fresh leaves into beds, because they tie up nitrogen.

Sheet (lasagna) composting

  • Build: layer cardboard, greens and browns right on the bed. Fall is best for spring planting; allow about 6 months.

  • Expect shrinkage: beds sink about half in the first year.

  • Planting early: put seedlings into pockets of finished compost.

Trench and pit composting

  • Depth: bury scraps at least 12 in deep under at least 8 in of soil to keep dogs and wildlife out.

  • Trenches: 12–18 in deep, filled in fall and planted over in spring.

Diagram coming soonLeaf mold cage
Figure 5. Leaf mold takes one to two years.
Sources: University of Georgia Extension, Royal Horticultural Society and 6 more

Using compost

  • Established beds: about ½–1 in a year.

  • New gardens: up to 2–3 in of plant-based compost, but only about 1 in of manure-based compost because of salt.

  • Without a soil test, Penn State suggests as little as ¼ in every few years, because phosphorus builds up.

  • More isn't better. Oregon State found home gardens averaging 13% organic matter against a 3–5% target.

  • Get a soil test every few years.

Sources: Rodale Institute, Charles Dowding and 3 more

What you'll need

  • Bin: pallets, wire fencing or hardware cloth, or a three-bin frame.

  • Long-stem compost thermometer (needed to know if you hit 131°F).

  • Pitchfork and a hose with a spray nozzle.

  • Worm bin: an opaque bin with air holes, bedding, and red wigglers from a known grower.

  • Bokashi: an airtight bucket with a drain spigot and inoculated bran.

  • Pea test: pots, potting mix and pea or bean seeds.

  • Dust mask for turning dry compost.

Costs not yet researched beyond Colorado State's bin estimates: pallet bin $5–25, three-chamber bin $20–80, plastic bins $80 to over $100 (prices undated).

Sources: Colorado State University Extension, NC State Extension and 2 more

Common mistakes

  1. Pile too small, so it never heats.

  2. Too wet (rotten-egg smell) or too dry (nothing happens).

  3. Assuming an old manure pile is composted.

  4. Spreading raw manure in spring before planting.

  5. Using pet waste.

  6. Bringing in hay, straw or manure without a pea test.

  7. Tilling fresh leaves into beds.

  8. Using worm-bin leachate on vegetables.

  9. Piling on compost every year without a soil test.

  10. Buying cheap mulch or worms that carry jumping worms.

Sources: NC State Extension, Cornell University and 6 more

Troubleshooting

ProblemCauseFix
Ammonia smellToo much nitrogenAdd browns
Rotten-egg smellToo wet, no airTurn; add dry browns; cover from rain
Pile won't heatToo small, dry or carbon-heavyMake it 3 ft+; water; add greens
Rats or raccoonsMeat or dairy, or uncovered foodRemove them; cover food with browns; ¼-in hardware cloth around the bin
Twisted, cupped tomato or bean leaves after adding manure or compostPersistent herbicideStop using that source; pea-test the rest; discard produce from injured plants if the chemical is unknown
Worm bin smells or worms fleeOverfeeding, too wet, or too hotFeed less; add dry bedding; move to shade
Weeds sprouting from compostPile didn't heat throughHot-compost weedy material, or keep it out
Sources: Cornell University, NC State Extension and 3 more

Resources

By zone

Cold winters stall piles and hot, dry summers dry them out. Here is what changes by zone and region.

3–4
Small piles freeze before heating. Start in May–June, or build a big pile in late summer to cure over winter. Worm bins go indoors (keep above about 55°F). Don't spread manure on frozen ground.
5–6
Larger piles (5 × 5 ft) keep working into winter. Apply raw manure in fall with a cover crop. Deep litter in winter coops.
7–8
Composting runs most of the year. Cover piles in heavy rain. Watch for jumping worms in bought mulch.
9–10
Heat speeds things up, but dryness slows them in the arid West: shade piles and water weekly. Worm bins need full shade. Go light on manure where soils are salty or alkaline.
Northeast
short season, so start piles in late spring and keep worm bins indoors.
Southeast
heavy rain, so cover piles and build them steep. Jumping worms are widespread.
Midwest
fall manure and cover crops, no spreading on frozen ground, jumping worms.
Southwest
shade and water piles, shape tops to catch water, skip wood ash, and watch salts.
Pacific Northwest
roof or cover bins through wet winters.
Mountain West
build bigger piles and water regularly.

Where this comes from

Every fact in this lesson was checked against 53 published sources: 50 from extension services, the USDA and research journals and 3 from experienced growers and practitioners. Each section lists its own at the bottom.

See all 53 sources
Washington State University Extension
Cornell Cooperative Extension
Iowa State University Extension
Royal Horticultural Society
University of Alaska Fairbanks Extension
University of Georgia Extension
University of Illinois Extension
University of Maryland Extension
Virginia Cooperative Extension
Wisconsin Department of Natural Resources

Summary

The whole lesson on one page. Print it or come back to it.

Key information

  • Mix browns and greens to about 30 parts carbon to 1 part nitrogen; keep it damp as a wrung-out sponge; build at least 3 × 3 × 3 ft.
  • The safety line is 131°F for 3 days (or 15 days with 5 turnings in a windrow).
  • Turn when the center cools, or above about 160°F. Expect 3–8 weeks hot, then 4–12 weeks curing.
  • Keep out meat, dairy, pet waste, diseased plants, black walnut and treated wood.
  • Pea-test outside hay, straw or manure for weed killers that survive composting.
  • Use about ½–1 inch a year in established beds, and soil-test every few years.

Step by step

  1. 1.Pick a spot: level, well-drained, near a water source. Shade it in hot, dry regions.
  2. 2.Build at least 3 × 3 × 3 ft in one go if you can, mixing or layering browns and greens and wetting each layer.
  3. 3.Check the heat with a long compost thermometer. A working pile heats within days.
  4. 4.Turn it when the center starts cooling, moving outside material to the middle, because the edges stay cooler.
  5. 5.If it passes about 160°F, turn it. Hotter than that kills the helpful microbes.
  6. 6.Active composting: about 3–8 weeks of hot work.
  7. 7.Cure: let it sit 4–12 weeks before use, longer for seed-starting.

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