title: "Composting Systems" subtitle: "A Complete Field Guide to Biological Decomposition for Soil Building" author: "Nored Farms" date: "2026"

Content Extraction Summary

**Hook Options:**

1. A properly managed compost pile hits 160°F internally — hot enough to kill every weed seed, every human pathogen, and most plant diseases — yet most backyard composters never get above 110°F because they treat composting like trash disposal instead of microbial engineering.

2. The Johnson-Su bioreactor produces fungal-dominant compost that increases crop yields 300–800% in peer-reviewed trials, and it requires zero turning for its entire 12-month cycle. The reason most extension offices still teach nitrogen-heavy, bacteria-dominant methods is because the fungal research is barely a decade old.

3. Your compost pile is a fermentation vessel. The same thermodynamic principles that govern beer brewing — substrate ratios, moisture content, oxygen availability, temperature curves — govern decomposition. Treat it like a bioreactor, not a garbage heap, and the output changes entirely.

**Key Mechanism:** Aerobic thermophilic decomposition — sequential microbial communities (mesophilic bacteria → thermophilic bacteria → actinomycetes → fungi) break down organic carbon chains and fix nitrogen into stable humus when provided correct C:N ratio (25–30:1), moisture (40–60%), and oxygen through turning or passive aeration.

**Misconception to Correct:** Composting is not slow. The Berkeley hot composting method produces finished compost in 18 days. What most people call "composting" — throwing scraps in a pile and waiting a year — is anaerobic neglect, not composting. The speed difference is entirely a function of oxygen, moisture, and carbon-to-nitrogen ratio management.

**Practical Application:** Any grower, homesteader, or farmer can build a thermophilic compost system for under $100 in materials and produce finished, pathogen-free soil amendment in 18–60 days depending on method. The same principles scale from a single 3×3×3 ft bin to 200-foot windrows.

**Citation-Ready Claims:**

  • Thermophilic composting at 55°C (131°F) sustained for 3 consecutive days eliminates human pathogens including E. coli, Salmonella, and helminth ova → USEPA 40 CFR Part 503 (1993); Wichuk & McCartney, 2007, *Compost Science & Utilization*
  • Johnson-Su bioreactor compost applied at 400 lbs/acre increased chile pepper yields 300% over control → Johnson & Su, 2016, *Sustainable Agriculture Research*
  • Vermicompost increases plant growth 20–40% compared to equivalent mineral fertilizer inputs → Arancon et al., 2004, *Pedobiologia*
  • Weed seed viability drops to zero at 60°C sustained for 72 hours → Dahlquist et al., 2007, *Weed Science*
  • Fungal-to-bacterial ratio in soil predicts plant community succession: annuals thrive in bacterial-dominant soil; perennials and woody plants require fungal-dominant soil → Ingham, 2005, *The Compost Tea Brewing Manual*

1. Introduction — Composting Is Microbial Engineering, Not Waste Disposal

The fastest compost method on earth — the Berkeley hot composting method developed at UC Berkeley in the 1950s — produces finished, usable compost in 18 days. Not months. Not a year. Eighteen days from raw feedstock to dark, crumbly, sweet-smelling humus that can go directly onto a garden bed.

Most people have never made compost that fast because most people have never been taught that composting is a biological process with specific input requirements. It is not "pile stuff up and wait." It is a managed aerobic fermentation with four critical control variables: carbon-to-nitrogen ratio, moisture content, oxygen availability, and particle size. Get all four right and the microbial community does the rest on a predictable timeline. Get any one wrong and the pile stalls, stinks, attracts pests, or sits there unchanged for years.

Thermophilic vs. Mesophilic

All composting operates through microbial decomposition, but the temperature range determines everything about the speed, safety, and output quality.

**Mesophilic composting** operates between 50–105°F (10–40°C). The organisms doing the work — mesophilic bacteria and fungi — are the same ones that decompose leaf litter on the forest floor. This is cold composting. It works. It takes 6–24 months. It does not reliably kill pathogens or weed seeds because it never gets hot enough.

**Thermophilic composting** operates between 105–160°F (40–71°C). A different community of heat-loving bacteria takes over once the pile crosses 105°F. These thermophiles metabolize organic matter far faster than mesophiles and generate enough heat to self-sterilize the pile. At 131°F (55°C) sustained for 3 days, human pathogens are eliminated. At 140°F (60°C) sustained for 72 hours, weed seeds are killed (Dahlquist et al., 2007). At 160°F (71°C), even heat-resistant plant diseases like clubroot and verticillium are destroyed.

The practical difference: thermophilic composting is faster, safer, and produces a more stable product. It requires more management (turning, moisture monitoring, feedstock balancing) but the return on that labor is measured in weeks instead of months.

Aerobic vs. Anaerobic

**Aerobic decomposition** uses oxygen. It is fast, relatively odorless, and produces CO₂, water, and humus. This is what you want.

**Anaerobic decomposition** occurs when oxygen is excluded. It is slow, produces methane, hydrogen sulfide (rotten egg smell), and organic acids. It creates a product that is phytotoxic — it will burn plant roots if applied directly. Anaerobic decomposition is what happens in landfills. It is what happens in a compost pile that is too wet, too compacted, or never turned.

There is one exception: bokashi. Bokashi is a deliberate anaerobic fermentation using specific lactobacillus cultures to pickle organic waste before burial. It works, but it is a pre-composting fermentation step, not composting itself. The bokashi product still needs to be buried or added to an aerobic pile to finish decomposing.

A Short History

Composting is older than agriculture. Any farmer who ever noticed that crops grew better where manure and straw had piled and rotted understood the principle. The first systematic written composting instructions appear in Marcus Porcius Cato's *De Agri Cultura* (160 BC), which describes layering animal manure, straw, and green vegetation in pits and turning the material periodically. Chinese agricultural texts from the same era describe similar practices.

The modern science of composting began with Sir Albert Howard's *An Agricultural Testament* (1940), which documented the Indore method — a layered composting system Howard developed in India that combined green waste, animal manure, and soil inoculant in specific ratios and turned on a fixed schedule. Howard's work established the C:N ratio principle that underlies every composting method used today.

The Berkeley method was developed by researchers at the University of California, Berkeley in the 1950s and refined by Robert Raabe. It optimized Howard's principles for speed: smaller particle size, tighter C:N control, and turning every other day to maintain aerobic conditions throughout the pile.

The most significant recent advance is David Johnson's fungal-dominant composting research at New Mexico State University, beginning around 2010. Johnson's bioreactor design produces compost with a fungal-to-bacterial ratio of 10:1 to 20:1 — dramatically higher than conventional compost — and his field trials have shown yield increases of 300–800% when applied as a soil inoculant (Johnson & Su, 2016). This work challenges the decades-old assumption that bacteria-dominant compost is the goal.

2. Source Materials — Carbon, Nitrogen, and the Ratio That Governs Everything

The single most important number in composting is the carbon-to-nitrogen ratio of the combined feedstock. The target is 25–30:1 by weight. This means 25–30 parts carbon for every 1 part nitrogen.

Why this ratio? Decomposer microorganisms use carbon as an energy source and nitrogen to build proteins and cell structures. At 25–30:1 C:N, the microbes have enough carbon to fuel their metabolism and enough nitrogen to reproduce rapidly. Below 20:1 (too much nitrogen), excess nitrogen is released as ammonia gas — that sharp smell in an overloaded compost pile — and the material becomes slimy. Above 40:1 (too much carbon), decomposition slows to a crawl because the microbes are nitrogen-starved. They will eventually break down the material, but it takes months or years instead of weeks.

Carbon Sources ("Browns")

| Material | C:N Ratio | Notes | |---|---|---| | Sawdust (hardwood) | 400:1 | Use sparingly; takes years alone. Mix heavily with greens | | Cardboard (corrugated) | 350:1 | Shred first. Remove tape and staples | | Newspaper (shredded) | 175:1 | Soy-based inks are safe; avoid glossy inserts | | Dry leaves (oak, maple) | 40–80:1 | Best brown for most backyard composters | | Straw (wheat, oat) | 75–100:1 | Excellent structure builder; keeps pile aerated | | Wood chips | 200–500:1 | Best for mulch, not compost, unless aged 6+ months | | Corn stalks (dry) | 60–75:1 | Chop to 2–4 inches for faster breakdown | | Pine needles | 80:1 | Slightly acidic; fine in moderation | | Paper (office, unbleached) | 150–200:1 | Shred. Avoid glossy or heavily printed stock |

Nitrogen Sources ("Greens")

| Material | C:N Ratio | Notes | |---|---|---| | Fresh grass clippings | 15–20:1 | Compact and go anaerobic quickly; mix with browns immediately | | Kitchen scraps (vegetable) | 15–25:1 | No meat, no dairy, no oils in open piles | | Coffee grounds | 20:1 | pH near neutral despite acidic taste; excellent green | | Fresh manure (chicken) | 7–10:1 | Highest N of common manures; use cautiously | | Fresh manure (horse) | 25–30:1 | Nearly balanced on its own; often contains weed seeds | | Fresh manure (cow) | 18–20:1 | Good general nitrogen source; usually pre-mixed with bedding | | Alfalfa hay/meal | 12–15:1 | Powerful nitrogen source; heats piles fast | | Seaweed/kelp | 19:1 | Excellent micronutrient source; rinse salt if coastal harvest | | Fresh weeds (pre-seed) | 20–30:1 | Only add weeds that have not set seed | | Legume cover crop residue | 10–15:1 | Best green available on a farm |

What to Never Add

  • **Meat, fish, dairy, oils** — attract rodents and raccoons in open systems; create anaerobic pockets; acceptable only in sealed bokashi or in-vessel systems
  • **Pet waste (dog, cat)** — may contain Toxoplasma gondii, roundworm, and other pathogens that survive even thermophilic temperatures
  • **Diseased plant material** — only safe in thermophilic systems confirmed at 140°F+ for 72 hours; when in doubt, burn it
  • **Treated lumber, painted wood** — arsenic (CCA-treated), lead (old paint), and other persistent toxins do not decompose
  • **Coal or charcoal ash from briquettes** — briquettes contain binders and lighter fluid residues; hardwood ash is fine in moderation (raises pH)
  • **Persistent herbicide residues** — aminopyralid, clopyralid, and picloram survive composting and kill broadleaf crops; common in hay from treated pastures; test any unknown hay source before composting

3. Equipment — From Free to Farm-Scale

Pallet Bin (Budget Tier — $0–$50)

The simplest effective compost bin is four wooden pallets stood on edge and wired together at the corners. Interior dimensions roughly 3×3×3 ft — the minimum volume for a thermophilic pile (1 cubic yard). This is the minimum because smaller volumes lose heat to the environment faster than biology can generate it.

**Build:** Stand four pallets vertically. Wire three corners permanently. Use two bungee cords or a latch on the fourth corner as a gate for turning access. Line the interior with hardware cloth (1/2 inch) if rodents are a concern. No floor — direct soil contact provides drainage and inoculates the pile with soil organisms.

**Three-bin system:** Build three pallet bins side by side. Bin 1 receives fresh material. When full, fork the contents into Bin 2 (first turn). When Bin 2 is ready for its next turn, fork into Bin 3. Bin 1 is now empty to receive new material. This rotation keeps three batches at different stages simultaneously.

Tumbler ($100–$400)

A sealed barrel on a frame that rotates for mixing. Good for small households, bad for serious volume. Advantages: rodent-proof, contained, easy to turn. Disadvantages: too small to sustain thermophilic temperatures reliably, expensive per cubic foot of capacity, batches cannot be mixed mid-cycle without disrupting the process.

Windrow (Farm Scale — $0 + labor or $5,000–$50,000 for equipment)

A windrow is a long, trapezoidal pile — typically 4–6 ft tall, 8–14 ft wide at the base, and as long as needed. This is the standard method for farm-scale and municipal composting. Turning is done with a tractor-mounted windrow turner or a front-end loader.

**Dimensions matter.** Too narrow and the pile loses heat. Too wide and the interior goes anaerobic because oxygen cannot penetrate. The ideal cross-section for a passively aerated windrow is roughly 5 ft tall × 10 ft wide. For mechanically turned windrows, wider dimensions are acceptable because turning re-introduces oxygen throughout.

Static Aerated Pile

PVC pipes (1.5–2 inch diameter, drilled with 3/8 inch holes every 6 inches) laid on the ground beneath the pile deliver air passively or with a low-volume blower (1/10 HP is sufficient for most homestead-scale piles). This eliminates the need for turning. The pile sits undisturbed for 30–90 days while air moves through the perforated pipe network.

Vermicompost Bin ($30–$150)

A shallow bin (12–18 inches deep) housing red wiggler worms (*Eisenia fetida*). Worms process food scraps at approximately half their body weight per day. A bin with 1 lb of worms processes roughly 3.5 lbs of food waste per week. The output — worm castings — is the highest-quality compost amendment available, gram for gram.

**Bin design:** Opaque plastic tote (10–18 gallon), drilled with 1/4 inch holes on the sides (upper third) for ventilation, and 1/8 inch holes on the bottom for drainage. Bedding: shredded newspaper or cardboard moistened to the consistency of a wrung-out sponge. Worms live in the bedding and migrate to food as it is added in shallow layers.

Monitoring Equipment

  • **Compost thermometer** ($15–$40): 20-inch stem, dial or digital. Measures core temperature. Non-negotiable for hot composting — you cannot manage what you do not measure.
  • **Moisture meter** ($10–$30): Probe-style. Insert into the pile; reading should be 40–60%. The squeeze test works too: grab a handful, squeeze hard. It should feel like a wrung-out sponge — a few drops of water, no stream.
  • **pH meter** ($15–$40): Finished compost should be 6.5–8.0. Below 6.0 indicates incomplete decomposition or anaerobic conditions.

4. Setup and Preparation

Site Selection

  • **Drainage:** Never place a compost pile in a low spot that collects standing water. Slight slope is ideal for leachate drainage.
  • **Shade:** Partial shade reduces moisture loss in hot climates. Full sun is fine in temperate and cool climates — it helps maintain temperature during shoulder seasons.
  • **Water access:** A hose within reach. You will need to add water. A dry pile is a dead pile.
  • **Distance from structures:** 10 ft minimum from buildings (pest management, odor management). Check local ordinances — some municipalities regulate placement.
  • **Soil contact:** Direct ground contact is preferred. Soil organisms inoculate the pile naturally. Concrete pads work for large-scale operations where leachate capture is required.

Initial Layering (for a new hot composting pile)

1. **Base layer:** 4–6 inches of coarse browns (small sticks, corn stalks, straw). This creates airflow channels at the bottom. 2. **Green layer:** 2–3 inches of nitrogen-rich material. 3. **Brown layer:** 4–6 inches of carbon-rich material. 4. **Repeat** until the pile reaches minimum 3 ft × 3 ft × 3 ft. 5. **Water each layer** as you build. Every layer should be moist but not dripping. 6. **Optional inoculant:** A shovelful of finished compost or native forest soil between every 3–4 layers introduces the microbial community. Not required but accelerates startup by 1–3 days.

**Target metrics at startup:**

  • C:N ratio: 25–30:1
  • Moisture: 50–60%
  • Particle size: 1–3 inches (smaller particles = faster decomposition, but too fine = compaction = anaerobic)
  • Minimum volume: 27 cubic feet (1 cubic yard / 3×3×3 ft)

5. Process Steps — Four Methods, One Goal

5A. Berkeley Hot Composting (18-Day Method)

The fastest reliable method. Developed at UC Berkeley. Produces finished compost in 18 days under ideal management.

**Requirements:**

  • All feedstock gathered and mixed before starting (no additions after Day 1)
  • Particle size: 0.5–1.5 inches (shred, chop, or run through a chipper)
  • C:N ratio: 25–30:1
  • Moisture: 50–60%
  • Minimum pile size: 3×3×3 ft (1 cubic yard)

**Schedule:**

| Day | Action | Expected Temperature | |---|---|---| | 1 | Build pile. Mix all materials thoroughly. Water to 50–60% moisture. | Ambient | | 2–3 | No turning. Let pile heat. | Rising to 130–150°F | | 4 | Turn pile completely (outside material to inside, inside to outside). | 130–160°F | | 6 | Turn pile. | 130–160°F | | 8 | Turn pile. | 130–150°F | | 10 | Turn pile. | 120–140°F | | 12 | Turn pile. | 110–130°F | | 14 | Turn pile. | 100–120°F | | 16 | Turn pile. | 90–110°F | | 18 | Finished. Pile temperature near ambient. Material is dark, crumbly, earthy-smelling. | Ambient |

**Critical rule:** Every turn moves outside material to the center and center material to the outside. This ensures every particle spends time in the thermophilic core. If any zone stays below 131°F (55°C) for the full cycle, pathogens in that zone may survive.

**If the pile does not heat:** The three most common causes are (1) not enough nitrogen — add fresh grass, manure, or alfalfa; (2) too dry — add water until the squeeze test produces a few drops; (3) pile too small — build it bigger.

5B. Cold Composting (Passive Method)

Pile materials as they become available. Turn occasionally — once a month is sufficient. Finished in 6–24 months depending on climate, moisture, and how often you turn.

This method is low-effort but does not kill pathogens or weed seeds reliably. It is appropriate when feedstock arrives in small, irregular quantities and the timeline is not critical.

**Best practice for cold composting:** Maintain a separate carbon stockpile (bale of straw, bag of leaves). Every time you add greens (kitchen scraps, grass clippings), cover with an equal volume of browns. This prevents odor, deters pests, and keeps the C:N ratio in the right range even without precise measurement.

5C. Vermicomposting

Worm composting operates at 55–77°F (13–25°C) — room temperature. The worms do the turning. The process takes 3–6 months per batch.

**Setup:** 1. Fill bin with 4–6 inches of moistened shredded newspaper or cardboard bedding. 2. Add 1 lb of red wigglers (*Eisenia fetida*) per 1 sq ft of bin surface area. 3. Bury food scraps under the bedding in a different corner each feeding. 4. Feed no more than the worms can process in 3–5 days. Overfeeding causes odor and fruit flies.

**What worms eat:** Vegetable and fruit scraps, coffee grounds and filters, tea bags (remove staples), crushed eggshells, shredded paper, small amounts of bread or pasta.

**What worms cannot handle:** Citrus in large quantities (too acidic), onion and garlic (repels worms), meat, dairy, oils, hot peppers.

**Harvesting:** When the bin is 70%+ castings, push all material to one side, add fresh bedding and food to the empty side. Within 2–3 weeks, worms migrate to the fresh side. Harvest the castings from the abandoned side.

5D. Bokashi (Anaerobic Fermentation)

Bokashi is not composting in the strict sense — it is a lactic acid fermentation that pickles organic waste, including meat and dairy, in a sealed anaerobic environment. The fermented material must then be buried in soil or added to an aerobic compost pile to finish decomposing.

**Process:** 1. Layer food waste in a sealed bucket with bokashi bran (wheat bran inoculated with *Lactobacillus* and other effective microorganisms). 2. Press down to eliminate air pockets. Seal tightly. 3. Drain leachate every 2–3 days from the spigot at the bottom. Dilute 100:1 with water for use as liquid fertilizer. 4. After 2 weeks sealed, the material is fermented. It will look largely unchanged but smell sour-sweet (like pickles, not rot). 5. Bury the fermented material 8–12 inches deep in garden soil. Soil organisms finish decomposition in 2–4 weeks.

**Advantage:** Handles meat, dairy, and cooked food that cannot go in open compost systems. Works indoors. No odor when sealed.

5E. Johnson-Su Bioreactor (Advanced Static Method)

Developed by David Johnson and Hui-Chun Su at New Mexico State University. This is a static (no-turning) fungal-dominant composting system that produces the highest-quality biological inoculant of any composting method currently documented in peer-reviewed literature.

**Design:** A 4-ft diameter, 5-ft tall wire cylinder lined with landscape fabric. Six 4-inch perforated PVC pipes inserted vertically through the pile provide passive aeration. The pile is built, watered, and then left undisturbed for 12 months.

**Construction:** 1. Form a cylinder from welded wire fencing (4 ft diameter × 5 ft height). Line interior with weed fabric or burlap. 2. Insert six 4-inch PVC pipes vertically, equally spaced, extending from the base to the top. Drill 3/8-inch holes every 4 inches along each pipe. 3. Fill the cylinder with a 1:1 mix (by volume) of wood chips and green waste (fresh manure, green plant material, food waste). 4. Water thoroughly until the entire mass is uniformly moist (60% moisture). 5. Cover the top with cardboard or burlap to reduce evaporation. 6. Water monthly to maintain moisture. Do not turn. Do not disturb. 7. After 12 months, the compost is finished. Remove the PVC pipes (they pull out cleanly, leaving aeration chimneys). The material will have colonized with visible white fungal mycelium throughout.

**Application:** Johnson-Su compost is not used as a bulk soil amendment. It is used as a biological inoculant — applied at 400 lbs/acre as a seed coating, transplant dip, or thin top-dressing. The active fungal community colonizes the root zone and establishes a mycorrhizal network that dramatically improves nutrient uptake. Johnson's field trials at NMSU showed chile pepper yield increases of 300% and cover crop biomass increases of 800% over uninoculated controls (Johnson & Su, 2016).

**Why it works differently:** Conventional hot composting favors bacteria because the frequent turning and high temperatures destroy fungal hyphae. The Johnson-Su bioreactor is never turned, and the passive aeration keeps temperatures in the mesophilic-to-low-thermophilic range (100–130°F) where fungi thrive. The 12-month timeline allows successive fungal communities to fully colonize the substrate.

6. Safety and Common Problems

Ammonia Smell (Sharp, Eye-Watering)

**Cause:** C:N ratio below 20:1 — too much nitrogen relative to carbon. Excess nitrogen volatilizes as ammonia gas. **Fix:** Add carbon. Straw, dry leaves, or shredded cardboard mixed into the pile. Turn to incorporate. The smell should dissipate within 24–48 hours.

Rotten Egg Smell (Hydrogen Sulfide)

**Cause:** Anaerobic conditions. The pile is too wet, too compacted, or both. Anaerobic bacteria are producing hydrogen sulfide and methane. **Fix:** Turn the pile immediately to re-introduce oxygen. If too wet, add dry carbon materials while turning. If severely compacted, break up clumps and add bulky browns (straw, small sticks) to create air channels.

Pile Does Not Heat

**Cause (most common to least common):** 1. Too dry — add water. 2. Not enough nitrogen — add fresh greens, manure, or alfalfa meal. 3. Pile too small — minimum 3×3×3 ft. 4. Particle size too large — chop or shred feedstock. 5. Cold ambient temperatures — insulate the pile with straw bales on the sides or a tarp over the top.

Pest Attraction

**Cause:** Exposed food scraps, especially meat or dairy in an open system. **Fix:** Always bury food scraps under 4–6 inches of browns. Never add meat, fish, dairy, or cooking oil to open piles. If rodents are persistent, line the bin floor and lower walls with 1/2-inch hardware cloth.

Weed Seed Survival

Weed seeds are killed at 140°F (60°C) sustained for 72 hours (Dahlquist et al., 2007). If your pile never reaches this temperature, weed seeds in the feedstock will survive and germinate when the compost is applied. This is the single strongest argument for managing pile temperature with a thermometer rather than guessing.

**Rule of thumb:** If you did not measure the core temperature above 140°F for at least 3 days, and if you did not turn the pile so all material rotated through the core, assume weed seeds survived.

Fire Risk

Extremely large piles (over 10 ft tall or windrows over 8 ft tall) can self-combust if internal temperatures exceed 200°F (93°C). This is rare in backyard systems but documented in farm-scale and municipal operations. Monitor temperature. If internal temp exceeds 170°F, turn the pile immediately to cool it and re-introduce moisture.

Human Health

Wear gloves when handling compost. Wear a dust mask when turning dry piles or screening finished compost — *Aspergillus fumigatus* spores are present in virtually all compost and can cause aspergillosis in immunocompromised individuals. If you are immunosuppressed, delegate compost turning to someone who is not.

7. Waste Handling and Byproduct Uses

Compost Tea

Compost tea is an aerated water extract of finished compost. It is used as a foliar spray or soil drench to deliver a concentrated dose of beneficial microorganisms.

**Brewing method (actively aerated compost tea / AACT):** 1. Fill a 5-gallon bucket with dechlorinated water (let tap water sit 24 hours, or use well water, or add 1 drop sodium thiosulfate per gallon to neutralize chlorine). 2. Add 1–2 cups of finished compost in a mesh bag (burlap, nylon stocking, paint strainer bag). 3. Add a microbial food source: 1 tablespoon unsulfured blackstrap molasses per gallon of water. 4. Insert an aquarium air pump with an airstone. Aerate continuously for 24–36 hours. 5. Remove the compost bag. Use the tea immediately — within 4 hours. Once aeration stops, anaerobic organisms begin to dominate and the product becomes potentially harmful.

**Application:** Foliar spray at dawn or dusk (UV kills microbes). Dilute 1:1 to 1:5 with water for soil drench. Apply every 2–4 weeks during the growing season.

**Note on compost tea claims:** Peer-reviewed evidence for compost tea as a disease suppressant is mixed. Some studies show clear suppression of foliar pathogens (Scheuerell & Mahaffee, 2002); others show no effect. The microbial composition of the starting compost determines the tea quality — tea made from poorly managed compost is worthless. The most consistent documented benefit is as a soil biology inoculant, not a disease treatment.

Leachate Management

Leachate is the liquid that drains from the bottom of a compost pile during rain or overwatering. It is not compost tea. Leachate may contain pathogens, anaerobic metabolites, and phytotoxic organic acids, especially from immature compost.

**Management:** On a well-drained site, leachate soaks into the ground and is filtered by soil. If your compost is on a concrete pad or impermeable surface, direct leachate to a planted area (not directly to food crops during the growing season). Do not apply raw leachate to edible leaf crops.

8. Storage and Application

Curing

Finished compost that has cooled to ambient temperature is technically usable, but curing for 2–4 weeks improves stability. During curing, the remaining easily decomposable compounds finish breaking down, and the microbial community shifts from decomposers to a stable, diverse soil community. Uncured compost applied directly can temporarily tie up nitrogen in the soil as residual carbon continues decomposing.

**Curing method:** Move finished compost to a covered area (tarp or shed). Keep it moist but not wet (30–40% moisture). No turning needed. After 2–4 weeks, the compost should have no heat when you insert your hand into the center of the pile, and it should smell earthy — not sour, not ammonia-like, not like anything decomposing.

Screening

For garden beds and potting mixes, screen finished compost through 1/2-inch hardware cloth to remove sticks, uncomposted chunks, and debris. The overs go back into the next batch. Screening is unnecessary for broad-acre field application.

Application Rates

| Application | Rate | Notes | |---|---|---| | New garden beds | 2–4 inches tilled into top 6 inches | One-time soil building; reduces to maintenance rate in year 2 | | Established garden beds | 1–2 inches top-dressed annually | Apply in spring before planting or in fall after harvest | | Lawn renovation | 1/4–1/2 inch top-dressed | Rake into existing turf; water in | | Fruit trees | 2–4 inches in a ring from drip line outward | Keep compost 6 inches from trunk to prevent crown rot | | Potting mix component | 25–40% by volume | Mix with perlite, peat or coco coir, and vermiculite | | Farm-scale field application | 3–10 tons/acre | Based on soil test results; apply before cover crop or cash crop | | Johnson-Su bioreactor inoculant | 400 lbs/acre | As seed coat or transplant dip, not bulk amendment |

Storage

Finished, cured compost stores for 6–12 months if kept covered and moist (30–40% moisture). Completely dried-out compost loses most of its biological activity — the microorganisms die. If storing long-term, cover with a tarp and water periodically to maintain moisture. Do not seal in airtight containers — the biology needs oxygen to stay alive.

9. Scaling — Farm-Scale Windrow Management

Windrow Dimensions

The standard farm-scale windrow is 4–6 ft tall, 10–14 ft wide at the base, and as long as feedstock allows. These dimensions balance heat retention (enough mass) against oxygen penetration (not so wide that the core goes anaerobic between turns).

Turning Schedule (Mechanically Turned Windrow)

| Phase | Duration | Turning Frequency | Temperature Target | |---|---|---|---| | Active thermophilic | Days 1–21 | Every 3–5 days | 131–160°F (55–71°C) | | Late thermophilic | Days 21–45 | Every 7–10 days | 110–140°F (43–60°C) | | Cooling/curing | Days 45–90 | Every 14 days or not at all | Declining to ambient |

USEPA 40 CFR Part 503 requires that windrow composting of biosolids maintain temperatures at or above 55°C (131°F) for 15 consecutive days, with a minimum of 5 turns during that period. For on-farm composting of manure and plant waste (not biosolids), the NOP (National Organic Program) requires 131°F for 15 days with 5 turns for windrows, or 131°F for 3 days for static aerated or in-vessel systems.

Temperature Monitoring

At farm scale, insert a 36-inch or 48-inch compost thermometer at three points along each windrow: both ends and the center. Record temperatures daily during the active phase. A windrow that drops below 110°F before Day 21 is either too dry, too carbon-heavy, or needs turning.

Moisture Management

At scale, windrows are watered during turning using a water truck or tractor-mounted spray bar. Rainfall provides supplemental moisture but is rarely sufficient alone. In arid climates, expect to add 50–100 gallons of water per cubic yard of feedstock over the composting cycle.

Equipment for Farm Scale

  • **Windrow turner** ($15,000–$150,000 new; $5,000–$40,000 used): Purpose-built machine that straddles the windrow and turns the entire cross-section in a single pass. The most efficient tool for operations handling 500+ cubic yards/year.
  • **Front-end loader** ($0 if already owned): Works for turning but mixes less thoroughly than a purpose-built turner. Acceptable for operations under 500 cubic yards/year.
  • **Compost screener** ($2,000–$30,000): Trommel or vibrating screen for sizing finished product. A 1/2-inch screen produces garden-grade compost; a 3/8-inch screen produces potting-grade.

10. Sources

1. Arancon, N.Q., Edwards, C.A., Bierman, P., Welch, C., Metzger, J.D. (2004). Influences of vermicomposts on field strawberries: effects on growth and yields. *Pedobiologia*, 48(1), 29–44. DOI: 10.1016/j.pedobi.2003.08.001

2. Dahlquist, R.M., Prather, T.S., Stapleton, J.J. (2007). Time and temperature requirements for weed seed thermal death. *Weed Science*, 55(6), 619–625. DOI: 10.1614/WS-07-047.1

3. Howard, A. (1940). *An Agricultural Testament*. Oxford University Press.

4. Ingham, E.R. (2005). *The Compost Tea Brewing Manual* (5th ed.). Soil Foodweb Inc.

5. Johnson, D.C., Su, H. (2016). Development of an innovative no-till, high-functioning microbial-rich compost system. *Sustainable Agriculture Research*, 5(3), 13–23.

6. Raabe, R.D. (2001). The rapid composting method. University of California Cooperative Extension publication.

7. Scheuerell, S., Mahaffee, W. (2002). Compost tea: principles and prospects for plant disease control. *Compost Science & Utilization*, 10(4), 313–338. DOI: 10.1080/1065657X.2002.10702095

8. USEPA (1993). Standards for the use or disposal of sewage sludge. 40 CFR Part 503. *Federal Register*, 58(32), 9248–9415.

9. Wichuk, K.M., McCartney, D. (2007). A review of the effectiveness of current time-temperature regulations on pathogen inactivation during composting. *Journal of Environmental Engineering and Science*, 6(5), 573–586. DOI: 10.1139/S07-011

10. Elaine Ingham, Soil Food Web School. Soil biology and fungal-to-bacterial ratio research. Multiple publications and presentations, 2000–2024.

`[soil-science]` `[growing]` `[practical-skills]` `[beginner]`