S4ag Storage

---
name: s4ag-storage
description: "On-farm storage guidance. Use when the user says 'how do I store', 'root cellar', 'grain bin', 'cold room', 'post-harvest', 'reducing losses', 'keep produce longer', 'storage temperature', or 'produce is spoiling'."
allowed-tools: [Read]
---

# Storage

Storage is where growing decisions pay off or are lost. A crop grown well can still arrive at market or table in poor condition if handling, curing, and storage conditions are wrong — and a crop grown on degraded soil will spoil faster regardless of how well you store it. Your goal is to extend the marketing and eating window without expensive infrastructure wherever possible, and to understand that shelf life begins in the field, not in the cold room.

**How this skill works:** Each sub-tool pauses at a **Checkpoint** to confirm the assumptions it is about to build on before producing output. A recommendation built on a wrong assumption wastes time and money — confirm the checkpoint before acting. Each sub-tool ends with **Next steps** — the skills worth running once you have acted on this one.

---

## Expert Lineage

*The thinkers whose frameworks underpin this skill — and what they specifically discovered that changes how you farm.*

**Mike and Nancy Bubel — Root Cellaring**
The Bubels wrote the definitive practical guide to traditional cold storage, documenting the temperature and humidity requirements for over 100 crops and the design principles of effective root cellars. Their most actionable finding: the single biggest root cellar failure is inadequate humidity control — not temperature — and many crops need near-100% humidity to avoid shrivelling. Most homemade cellars are too dry. Their species-by-species tables remain the most reliable storage parameter reference available.

**Eliot Coleman — Post-Harvest Handling at Market Scale**
Coleman's work on small-scale market farming includes the clearest account of how post-harvest handling affects shelf life and market quality in a direct-sales context. His specific contribution: field heat removal in the first two hours after harvest is the single highest-leverage post-harvest intervention — more important than storage temperature thereafter. A crop that enters storage warm will degrade faster than one stored at slightly warmer temperature after prompt field-heat removal.

**USDA AMS — Storage Parameter Science**
The USDA Agricultural Marketing Service publishes the empirical temperature and humidity data underpinning all commercial produce storage. Their core finding: storage life roughly doubles for every 10°C (18°F) reduction in temperature for most produce. This simple rule explains why cold storage investment pays at almost any scale — even a basic cooler is transformative compared to ambient storage.

**William Albrecht — Nutritional Quality and Storage Life**
Albrecht's work on mineral balance and crop quality has direct implications for storage: crops grown on balanced mineral soils with adequate calcium have better cell wall integrity and significantly longer storage life. Calcium deficiency is the leading cause of physiological storage disorders — bitter pit in apples, blossom-end rot in tomatoes, tip burn in lettuce. High-potassium soils produce lush, rapidly growing crops that store badly. Mineral balance in the field determines storage outcome in the shed.

**Elaine Ingham — Soil Biology and Produce Quality**
Ingham's soil food web framework connects to storage in a way most farmers don't track: biological soil management produces crops with lower nitrate content, better sugar development, and stronger cell walls. High-nitrate crops (from excess soluble nitrogen) are soft, watery, and store badly. Crops grown on a functioning food web — where N is released slowly by biology — develop more slowly, with firmer texture and better keeping quality. The food web is a post-harvest investment.

**Charles Benbrook — Pesticide Residues and Post-Harvest**
Benbrook's research on pesticide residues in food documented that post-harvest fungicide and waxing treatments are among the highest-residue interventions in the food system. His work supports the case for biological post-harvest treatments (hot water, UV, Bacillus subtilis) as effective and residue-free alternatives for direct-market producers. The post-harvest chemical toolkit is often more hazardous than field applications.

---

## Which tool fits

| You need to... | Tool |
|---|---|
| Design or manage a root cellar for vegetables | root-cellar |
| Store grain safely after harvest | grain-storage |
| Set up refrigeration or cool storage for fresh produce | cold-storage |
| Reduce losses from harvest damage, bruising, or poor handling | post-harvest-handling |

## Routing Decision

- **Storing roots, winter squash, apples, or cured alliums without refrigeration** → root-cellar
- **Storing wheat, oats, rye, beans, or other dry grains and seeds** → grain-storage
- **Keeping fresh produce, salad, brassicas, or soft fruit market-quality** → cold-storage
- **Losing produce to bruising, rotting in storage, or short shelf life** → post-harvest-handling
- **Unsure where losses are coming from** → post-harvest-handling first; it identifies where in the chain the problem lies

---

## Root Cellar

*Designs, manages, and troubleshoots traditional cold and cool storage for vegetables, fruit, and alliums.*

A root cellar uses the earth's thermal mass to hold temperature in the 0–10°C range without refrigeration. It suits crops that need cool, moist conditions for weeks to months: potatoes, carrots, beets, turnips, celeriac, parsnips, cabbage, and apples. Not every crop belongs in the same cellar — temperature and humidity requirements differ enough that mixing incompatible crops causes losses.

**Step 1: Understand the two storage environments**

Most root cellars need two distinct zones:

| Zone | Temperature | Humidity | Crops |
|---|---|---|---|
| Cold and moist | 0–4°C (32–40°F) | 90–95% | Carrots, beets, parsnips, celeriac, turnips, cabbage, leeks |
| Cool and moist | 4–10°C (40–50°F) | 85–90% | Potatoes, kohlrabi, winter pears |
| Cool and dry | 4–10°C | 60–70% | Garlic, onions, shallots |
| Mild and dry | 10–15°C (50–60°F) | 60–70% | Winter squash, pumpkins, sweet potatoes |

The most common mistake: putting all produce in one space at one temperature. Onions stored with apples will sprout. Squash stored at 4°C will develop chilling injury and rot within weeks.

**Step 2: Design and siting**

Key design variables:
- **Insulation:** The cellar needs to be insulated from the building above, not from the earth below. Heat loss is upward; earth provides the cooling.
- **Ventilation:** Two vents — one low (cold air in), one high (warm air out) — allow temperature control. Without ventilation, CO2 builds up and off-gassing from stored produce accelerates spoilage.
- **Humidity:** Most cellars need a moisture source — a pan of water, damp sand, or wet gravel floor. Bare concrete dries air. Humidity below 80% shrivels roots within weeks.
- **Darkness:** Essential — light triggers sprouting in potatoes and onions.
- **Access:** Weekly inspection access is required. Unseen problems become large losses.

**Siting options by scale:**

| Option | Cost | Capacity | Best for |
|---|---|---|---|
| In-ground insulated pit | Very low | 100–500kg | Small farms, homesteads |
| Basement cold corner | Low | 200kg–1 tonne | Existing basement with north-facing foundation |
| Buried container | Moderate | 500kg–2 tonnes | No basement; good for root crops |
| Purpose-built earthed room | High | 1–5 tonnes | Serious market garden storage |

**Step 3: Managing the cellar through the season**

- **Autumn:** Vent fully to draw in cool autumn air. Target temperature before crops go in.
- **Winter:** Reduce ventilation. Monitor temperature weekly — freeze events can damage produce.
- **Late winter:** Watch for sprouting and increase inspection frequency. Remove any rotting produce immediately — one rotting apple or carrot accelerates its neighbours.
- **Spring:** Temperature rises despite insulation. Move to refrigeration for late-stored crops or plan to have sold or processed stock before the cellar warms.

**Curing before storage — the step most growers skip:**

| Crop | Curing conditions | Duration | Why it matters |
|---|---|---|---|
| Potatoes | 10–15°C, high humidity, dark | 10–14 days | Skin set; wound healing reduces rot entry |
| Winter squash | 27–29°C, low humidity | 10 days | Skin hardens; sweetness develops |
| Garlic and onions | 27–35°C, low humidity, airflow | 2–4 weeks | Outer skins dry; neck seals; disease resistance |
| Sweet potatoes | 27–30°C, high humidity | 10–14 days | Suberisation heals harvest damage |

Skipping curing for these crops significantly reduces storage life. Potatoes that bypass curing enter storage with open wounds that become rot entry points within weeks.

**Checkpoint — confirm before finalising:**
- What crops are being stored, and do they share compatible temperature and humidity requirements?
- What space is available, and does it have access to external ventilation (wall to outside, or ground-level)?
- Is this for home use, or does it need to hold commercial stock for weeks-to-months with reliable quality?

A root cellar designed for potatoes that also receives winter squash will produce poor results for both — confirm the crop mix before designing the space.

**Output:**
```
ROOT CELLAR PLAN

CROPS TO STORE
[Crop]: [temperature target] / [humidity target] / [expected storage duration]
[Crop]: [temperature target] / [humidity target] / [expected storage duration]

STORAGE ZONE LAYOUT
Zone A — [temperature/humidity]: [crops assigned]
Zone B — [temperature/humidity]: [crops assigned]

CURING REQUIREMENTS BEFORE STORAGE
[Crop]: [conditions] for [duration]

DESIGN RECOMMENDATIONS
Insulation: [specification]
Ventilation: [inlet/outlet position and sizing]
Humidity management: [method]

MONITORING SCHEDULE
Weekly: [what to check]
Monthly: [what to inspect]

ESTIMATED BUILD COST: [£/$ range]
CAPACITY: [approximate kg/tonnes]
```

**Next steps:**
- run post-harvest-handling (within this skill) — curing and handling before storage determines storage success.
- `/s4ag-vegetables` — crop-specific growing decisions that affect storage quality.
- `/s4ag-seasons` — plan harvest timing so crops enter storage in prime condition, not past peak.

---

## Grain Storage

*Determines the right storage method for dry grains, seeds, and legumes — and manages the risks of moisture, insects, and rodents.*

Grain storage fails in three ways: moisture, insects, and rodents. Get moisture right and the other two become manageable. Get moisture wrong and no amount of pest control will save the grain.

**The fundamental rule: moisture content before anything else**

| Grain | Safe storage moisture content |
|---|---|
| Wheat, rye, triticale | Below 14% |
| Oats | Below 13% |
| Maize/corn | Below 14% |
| Barley | Below 14% |
| Dry beans and peas | Below 14% |
| Sunflower seed | Below 10% |
| Soybeans | Below 13% |

Above these thresholds: mould, mycotoxin production, and heating begin within days to weeks. Test moisture before storing. A cheap moisture meter (£30–50) prevents expensive losses.

**Harvest timing and field drying:**

Natural field drying is the most energy-efficient drying method available. For small-scale grain:
- Harvest at 16–18% if combining — then dry artificially or in windrow.
- Delay harvest until natural drying reaches safe MC if weather allows.
- In wet harvests, combine damp and dry with forced air — never store above 16% without active drying.

**Storage systems by scale:**

| Scale | System | Best for |
|---|---|---|
| Under 5 tonnes | Sealed bins (grain bags, airtight drums, silo bags) | Homestead, seed saving |
| 5–50 tonnes | Steel grain bins with aeration fans | Small-scale market grain |
| 50+ tonnes | Grain flat stores or silos with temperature monitoring | Commercial grain |

**Airtight/hermetic storage — the underused option:**

Hermetic storage (sealed grain bags or airtight containers) creates a modified atmosphere as grain respires — CO2 builds up, O2 drops, and insects and moulds cannot survive. Effective without chemical treatment. Widely used in developing world contexts; increasingly available for small-scale producers in the West. Grain Bag (silo bag) systems are low-cost and highly effective.

Requirements: grain must be at or below safe MC before sealing. Sealing high-moisture grain in an airtight environment accelerates mould rather than preventing it.

**Insect management:**

| Pest | Indicator | Response |
|---|---|---|
| Grain weevils | Grain dust, heating, sweet smell | Cool grain (below 10°C eliminates populations); hermetic sealing |
| Moth larvae | Webbing on grain surface, silk threads | Cool grain; thorough bin cleaning before new crop |
| Grain beetles | Live beetles in grain sample | Diatomaceous earth (DE) as physical control; cool storage |

Chemical treatments (phosphine fumigation, stored grain insecticides) are effective but require licensing and specific equipment. For small-scale producers, temperature management (cooling below 10°C) and hermetic sealing are safer and often more practical.

**Rodent exclusion:**

No storage system works without rodent exclusion. Minimum requirements:
- Metal bins or containers (rodents cannot chew through steel).
- No grain spillage around the storage building.
- Perimeter exclusion: sealed concrete floors, metal sills on doors.
- Snap traps or bait stations as secondary control — not as primary prevention.

**Soil health connection:**

Grain grown on biologically active soils with balanced mineral nutrition has lower moisture content at harvest maturity and better grain density (test weight) than grain grown on high-nitrogen, low-biology systems. High-nitrogen grain grown for maximum yield has softer grain, higher moisture, and stores less well. The food web investment shows up in the grain bin.

**Checkpoint — confirm before finalising:**
- What grain is being stored, and has moisture content been tested at harvest?
- What volume needs storing, and for how long?
- Is chemical treatment acceptable, or is a non-chemical approach required?

Recommending an airtight storage system for grain above 14% MC will produce mould — confirm moisture content before specifying the storage method.

**Output:**
```
GRAIN STORAGE PLAN

GRAIN: [species]
QUANTITY: [tonnes]
MEASURED MOISTURE CONTENT: [%] — [safe to store / requires drying]

DRYING REQUIREMENT (if applicable)
Method: [forced air / natural field drying / artificial dryer]
Target MC: [%]

STORAGE SYSTEM
Type: [hermetic / ventilated bins / flat store]
Capacity: [tonnes]

INSECT MANAGEMENT
Method: [cooling / hermetic / DE / monitoring schedule]

RODENT EXCLUSION
Measures: [metal bins / sealed building / trapping]

MONITORING
Temperature check: [frequency]
Moisture check: [frequency]
Inspection: [frequency]

EXPECTED STORAGE DURATION: [months]
```

**Next steps:**
- `/s4ag-grains` — harvest timing and grain development decisions that affect storage quality.
- run post-harvest-handling (within this skill) — handling at harvest determines grain condition entering storage.
- `/s4ag-seeds` — seed saving from grain crops has additional moisture and viability requirements.

---

## Cold Storage

*Selects and manages refrigerated storage for fresh produce — from simple coolers to walk-in cold rooms.*

The most important thing to know about cold storage is that it does not fix produce that was handled badly after harvest. Rapid field heat removal and careful handling matter more than perfect storage temperature — cold storage preserves quality, it does not restore it.

**Temperature and humidity by produce category:**

| Category | Temperature | Humidity | Notes |
|---|---|---|---|
| Salad leaves | 1–4°C | 95–100% | Highest priority for cold — fastest deterioration |
| Brassicas | 1–4°C | 90–95% | |
| Root vegetables (trimmed) | 0–4°C | 90–95% | |
| Cucumbers | 10–13°C | 90–95% | Chilling injury below 10°C |
| Courgettes / zucchini | 7–10°C | 90–95% | |
| Tomatoes (ripe) | 10–13°C | 85–90% | Cold damage below 10°C ruins flavour |
| Tomatoes (green) | 12–15°C | 85–90% | |
| Peppers | 7–13°C | 90–95% | |
| Soft fruit | 0–2°C | 90–95% | Immediately after harvest |
| Herbs (delicate) | 4–7°C | 90–95% | Not below 4°C — chilling injury |
| Eggs | 4–7°C | 70–80% | Low humidity — no condensation |

**The ethylene problem:**

Ethylene is a ripening gas produced by some produce types that accelerates ripening and deterioration in others. Never store ethylene-producing and ethylene-sensitive produce together.

| High ethylene producers | Ethylene sensitive |
|---|---|
| Apples, pears | Broccoli, Brussels sprouts |
| Tomatoes, avocados | Carrots, cucumbers |
| Stone fruit | Leafy greens, herbs |
| Kiwi | Potatoes (sprouting) |

Storing apples near broccoli in the same cold room will cause broccoli to yellow rapidly. Mixed cold rooms require either ethylene scrubbers or careful segregation.

**Cold storage options by scale:**

| Option | Capital cost | Capacity | Best for |
|---|---|---|---|
| Modified chest freezer (Coolbot or equivalent) | £200–600 | 100–300kg | Market garden start-up; space-limited |
| Small cool room (purpose-built or converted) | £1,000–4,000 | 0.5–2 tonnes | Small market garden with multiple crops |
| Walk-in cool room | £3,000–12,000 | 2–10 tonnes | Established market garden or small farm |
| Refrigerated trailer | £4,000–15,000 | 2–8 tonnes | Mobile; multi-market; harvest flexibility |

**The Coolbot approach:**

A standard window air conditioning unit paired with a Coolbot (or similar) controller can produce cold room temperatures at a fraction of the cost of commercial refrigeration. Effective down to around 1–2°C. This is the most accessible route into cold storage for small-scale producers. Key requirements: well-insulated room (minimum 100mm PIR insulation), no air leaks, correctly sized AC unit.

**Managing the cold chain for market sales:**

- Pre-cool produce to storage temperature before packing.
- Pack into chilled boxes or insulated containers — not at ambient temperature.
- At market: ice in display boxes, cooler bags for sale items, keep produce off the sun.
- Unsold produce: return to cold storage the same day. Produce left in a warm van overnight loses days of shelf life.

**Sustainable note:**

Passive cooling systems — cool rooms ventilated by night air, insulated shade structures in hot climates, evaporative coolers — can extend produce life significantly at very low energy cost in appropriate climates. Before investing in mechanical refrigeration, assess whether passive or low-energy systems can meet the need.

**Checkpoint — confirm before finalising:**
- What produce types are being stored — and are they compatible (ethylene producers and sensitive crops can't share space)?
- What is the marketing window — how many days does the produce need to hold quality?
- Is existing infrastructure available to convert, or is this a new build?

A cold room recommendation that assumes compatible ethylene profiles across mixed produce will produce unexpected losses — confirm the crop mix and the storage duration needed before specifying the system.

**Output:**
```
COLD STORAGE PLAN

PRODUCE TO STORE
[Produce]: [temperature] / [humidity] / [ethylene status]
[Produce]: [temperature] / [humidity] / [ethylene status]

ETHYLENE CONFLICTS
[any incompatible combinations — separate zones required]

SYSTEM RECOMMENDATION
Type: [Coolbot / cool room / walk-in / other]
Temperature target: [°C]
Humidity management: [method]
Capacity: [kg or crates]

COLD CHAIN PROCESS
At harvest: [action]
At packing: [action]
At market: [action]
Unsold return: [action]

ESTIMATED CAPITAL COST: [£/$]
ESTIMATED RUNNING COST: [£/$ per month]
```

**Next steps:**
- run post-harvest-handling (within this skill) — field heat removal before cold storage is more important than storage temperature.
- `/s4ag-market` — cold chain management directly affects what you can sell and at what price.
- `/s4ag-direct-marketing` — premium produce from cold chain-managed stock commands higher prices.

---

## Post-Harvest Handling

*Identifies where losses are happening between harvest and storage or sale, and fixes the specific handling failures causing them.*

Post-harvest losses on small farms typically run 20–40% of production value. Most of these losses are preventable with better handling technique rather than infrastructure investment. This sub-tool works through the post-harvest chain step by step to find where losses are occurring.

**The post-harvest chain:**

```
Harvest → Field holding → Field heat removal → Grading and sorting → Packing → Storage → Distribution → Sale
```

Losses can enter at any point. The most common entry points:

**1. Harvest timing**

| Sign | Implication |
|---|---|
| Harvesting mid-day in summer | Produce at maximum field heat — fastest deterioration |
| Over-mature at harvest | Short storage life regardless of conditions |
| Under-mature at harvest | Poor flavour; some crops (tomatoes, squash) do not ripen correctly off the plant |
| Rain damage or splitting | Enter storage cracked — immediate rot site |

Rule: harvest in the coolest part of the day (early morning or evening). Produce harvested at 6am at 15°C holds quality dramatically better than the same crop harvested at 2pm at 28°C.

**2. Field heat removal**

Field heat removal in the first 2 hours after harvest is the single most important intervention in the post-harvest chain.

| Method | How it works | Best for |
|---|---|---|
| Hydrocooling | Immerse in ice water — fastest method | Soft fruit, salad, brassicas |
| Forced air cooling | Move cool air rapidly over produce | Mushrooms, herbs, cut flowers |
| Cold room or cool water dump | Standard refrigeration after harvest | All produce types |
| Shade and airflow | Minimum viable — for immediate sale only | No cold storage available |

Never stack unharvested produce in direct sun while harvesting continues. Stack in shade, and move into cooling as soon as possible.

**3. Grading and sorting**

Grade out damage, disease, and culls at this stage — not in storage. Damaged produce in storage spreads rot to its neighbours. Any produce entering storage should be clean, undamaged, and dry.

- Remove field soil before storage (increases fungal disease pressure if left on).
- Do not wash unless required — wet surfaces in storage promote rot. Wash immediately before sale.
- Sort by size and maturity — different sizes store for different durations.

**4. Packing**

Bruising during packing is a major hidden loss cause. Common packing mistakes:

| Mistake | Consequence | Fix |
|---|---|---|
| Overfilling containers | Weight bruising on bottom produce | Fill to capacity without overpacking |
| Dropping produce into bins | Impact bruising | Lower gently; padded surfaces |
| Packing wet produce | Fungal growth in storage | Dry surface before packing |
| Mixed maturities in same pack | Fast-ripening items trigger others | Grade by maturity before packing |

**5. Storage environment (brief — see root-cellar and cold-storage sub-tools for detail)**

Most common storage environment failures:
- Temperature too high — accelerated deterioration across all produce types.
- Humidity too low — shrivelling and weight loss, reducing sale value.
- No airflow — CO2 and ethylene build up in packaged produce; promotes decay.
- Mixed incompatible produce — ethylene, odour transfer, humidity conflicts.

**6. Diagnosing where losses are occurring**

Work through these diagnostic questions:

- When is the loss occurring — in storage, at market, in transit?
- What does the loss look like — soft rot, dry shrivelling, off-flavour, yellowing?
- When in the season does it get worse?

| Symptom | Likely cause | Fix |
|---|---|---|
| Soft rot in storage | Wet produce at packing; harvest damage; too warm | Dry before storage; grade out damage; cool promptly |
| Shrivelling | Humidity too low | Add humidity source; improve packaging to retain moisture |
| Yellowing of brassicas or salad | Ethylene exposure; too warm | Separate from ethylene producers; reduce temperature |
| Off-flavour in stored roots | Freeze damage or too warm | Check temperature; improve insulation |
| Sprouting in potatoes or onions | Light exposure or too warm | Darkness; cooler temperature |
| Short shelf life in soft fruit | Not cooled promptly after harvest | Hydrocool within 1 hour of harvest |

**Soil health connection:**

Crops grown on biologically active soils with adequate mineral nutrition — particularly calcium — have better cell wall integrity and significantly longer post-harvest life. The single most effective post-harvest decision a market gardener can make is building calcium-rich, biologically active soil. Foliar calcium applications (calcium nitrate or chelated calcium) in the 4 weeks before harvest extend post-harvest life in leafy crops and brassicas by improving cell wall strength.

Conversely: crops grown on high-soluble-nitrogen regimes are lush, watery, soft, and store badly. The fertiliser choice in the field is a post-harvest decision.

**Checkpoint — confirm before finalising:**
- Where in the chain are losses occurring — at harvest, in storage, at market, or in transit?
- What produce types are affected?
- Is the primary loss cause physical damage, disease, or environmental (temperature, humidity)?

A diagnosis without locating the loss point in the chain produces general advice that may not address the actual problem — confirm where the losses are before specifying the fix.

**Output:**
```
POST-HARVEST LOSS AUDIT

LOSS LOCATION
Primary loss point: [harvest / field holding / cooling / storage / packing / distribution / market]

LOSS TYPE
[Symptom]: [likely cause]

HARVEST PROTOCOL FIXES
[specific changes to harvest timing and method]

COOLING PROTOCOL FIXES
[field heat removal method and timing]

HANDLING AND PACKING FIXES
[specific changes to sorting, packing, container use]

STORAGE ENVIRONMENT FIXES
[temperature / humidity / airflow / ethylene management]

SOIL HEALTH NOTE
[any upstream soil management changes that will improve storage quality]

PRIORITY ACTION
First fix: [the single highest-leverage change]
Second fix: [next]
Third fix: [next]

EXPECTED IMPROVEMENT: [estimated reduction in losses]
```

**Next steps:**
- run cold-storage (within this skill) to install or improve refrigeration if temperature is the identified failure point.
- `/s4ag-soil` — if short shelf life is systemic, the soil biology and mineral balance is the upstream fix.
- `/s4ag-market` — better post-harvest handling changes what produce quality you can confidently sell and at what price.