By Lukie Pieterse, Potato News Today

A deep dive into how modern potato storage can either quietly protect value or quietly destroy it – and why managing the pile well has become one of the most important resilience tools in a harsher climate.

Most potato stories are told in the open air: planting windows, rain at the wrong time, heat during bulking, disease pressure, harvest conditions. But in truth, a huge part of every season plays out in the dark.

Once the last truck tips and the doors close, the crop stops being a field of plants and becomes something else – a living pile, slowly respiring, aging, and reacting to every decision taken in that storage. What happens over the next few weeks and months can quietly add value, or erase it.

This article focuses on that second half of the season. It looks at how post-harvest management can either cushion the shocks delivered by climate and field conditions – or amplify them into a financial disaster.

Storage is not the epilogue – it is the second act

In many business plans and public debates, storage is still treated as a footnote: a cost line, a necessary piece of infrastructure. On farms, it sometimes slips into the background once the busy noise of harvest has passed.

Yet practically:

• a clean, well-managed store can turn an average crop into a decent season by preserving quality and buying time to sell,
• a stressed, poorly run store can turn a good crop into a mess of breakdown, shrink and rejections.

Storage is where:

• heat at harvest either gets safely bled off or lingers as rot and sprouting risk,
• minor bruising either dries and stabilises or becomes a starting point for disease,
• small differences in field maturity and skin set either remain manageable or turn into silver scurf and fusarium problems.

The pile is not inert. It breathes, heats, sweats and ages. The whole point of modern potato storage is to shape that biological process, not simply contain it.

How the season walks into the store

A storage season does not start when the first fan comes on. It starts in the field.

Three pre-harvest factors set the tone inside the pile:

• Maturity and skin set – immature tubers with poor skin set are more prone to damage, moisture loss and disease entry. Pushing harvest early under contract pressure or weather fear often means storing a crop that simply is not ready for months in the dark.
• Weather around harvest – hot, dry conditions drive crop temperatures up; wet, cold conditions load extra free moisture and mud into the store. Both extremes create management headaches: heat means more respiration and faster disease development; free moisture fuels soft rots and makes ventilation less effective.
• Field health – late blight in the tops, soft rot in low spots, blackleg, bruising from rutted fields – all those field issues travel in with the crop. A sick field rarely becomes a healthy pile just because the crop went through a piler.

Good storage management starts with acknowledging that reality honestly. A store manager who knows they are dealing with hot, immature or diseased tubers can adapt strategy. One who pretends every load is “normal” is already on the back foot.

Heat, wounds and water – the risk triangle

Three things quietly drive trouble in the early storage period:

• tuber temperature,
• mechanical damage,
• and surface moisture.

Heat means higher respiration. Potatoes are living tissue; they convert starch to energy and give off heat and water vapour in the process. The warmer they are, the faster they respire and the more heat they generate. A warm pile tries to warm itself further. Without enough airflow and cooling capacity, that becomes a self-reinforcing hotspot.

Wounds – from harvesters, conveyors, drops, clods and stones – create entry points. Every bruise, cut or shatter bruise on a tuber invites bacteria and fungi to move in.

Free water – from rain-wet skins, condensation or wash water – helps pathogens move and multiply. Wet surfaces close off lenticels, suffocate tissues and create the conditions for soft rots to explode.

When all three coincide – warm tubers, fresh wounds and free water – the risk curve steepens dramatically. The priorities in the first days and weeks in store are therefore simple, but not easy:

• get the heat out,
• dry the skins,
• and heal the wounds.

The cure period: where seasons are often won or lost

The initial “curing” or wound-healing period is one of the most critical phases in storage.

The aims are to:

• allow periderm to repair itself at wound sites,
• encourage skin to finish setting,
• and avoid stressing tubers so much that they either rot or break dormancy early.

This usually means:

• holding temperatures moderately warm (for example, in the low teens °C, depending on market) for a limited period,
• maintaining high relative humidity so that tubers do not desiccate while healing,
• and ensuring enough airflow to remove the heat of respiration without chilling or overdrying the surface.

If the crop came in hot, this period also includes an initial pull-down: carefully stepping temperatures down from field level to a safer holding range without causing condensation.

Mistakes here tend to compound:

• pulling the temperature down too fast can cause condensation and stress, opening wounds instead of closing them,
• keeping temperatures too high for too long accelerates disease, sugar accumulation or sprouting risk,
• poor air distribution leaves parts of the pile effectively uncurated – wet, warm pockets of trouble that only become obvious later.

A well-managed cure period sets up the rest of the storage season. A badly managed one forces the operator into months of firefighting.

Airflow, temperature and humidity: steering a living mass

Once curing is complete, the task shifts from triage to holding: keeping the pile in a narrow band of temperature and humidity that preserves quality and minimises losses.

Three principles matter most:

• Even airflow – air must reach all parts of the pile, not just the easiest channels. Blocked ducts, uneven loading, overfilled bays and poor baffling create dead zones where heat and moisture accumulate.
• Stable temperature – frequent swings in temperature stress tubers, promote condensation and can trigger premature sprouting or sugar shifts in processing potatoes. A slow, well-managed pull-down to final holding temperature, followed by tight control, is far better than a series of “on/off” jolts.
• High, but not saturated, humidity – relative humidity should be high enough to minimise shrink, but not so close to saturation that condensation becomes constant. The exact balance depends on store design and crop condition.

Even with modern systems, this is a balancing act. Cold outside air may be dry, risking shrink if overused; warm, humid air in a mild winter may cool little but add to moisture problems. Mechanical refrigeration offers more control, but at significant energy cost.

Operators increasingly rely on:

• continuous monitoring of air and tuber temperatures at different depths,
• automatic controls that adjust fan speed, louvre position and cooling based on setpoints,
• and, in more advanced setups, differential pressure sensors to verify airflow patterns.

Where those tools are absent or limited, experienced store managers often substitute with something harder to quantify but very real – a feel for how the pile responds when they change a setting. That judgement remains one of the most valuable, and least visible, skills in the industry.

Climate volatility and the new storage stresses

Climate change does not only affect the field. It is quietly reshaping storage risk too.

Patterns that many operators now recognise include:

• hotter harvests, with tubers coming into store at temperatures that would have been unusual a generation ago,
• more intense rainfall events that make it difficult to avoid bringing in mud, free water and diseased vines,
• warmer, more humid winters that reduce the cooling effect of ambient air and stretch mechanical refrigeration systems,
• more frequent mid-winter thaws that push outside conditions above desired storage temperatures for days or weeks.

In this context:

• cooling capacity that was adequate for yesterday’s harvest temperatures can be stretched thin,
• energy consumption rises as fans and refrigeration work harder to maintain setpoints,
• and the margin for error around ventilation and humidity control shrinks.

Storage design is having to catch up: better insulation, more flexible ventilation options, variable-speed fans, and in some cases alternative or backup energy sources to cope with grid instability and price spikes.

From energy cost to energy risk

Energy was once a relatively predictable input. Today it is a serious risk factor.

• Price volatility can turn a marginal season into a loss if storage must run hard to compensate for a hot harvest or warm winter.
• Grid reliability issues, even short outages, can cause temperature spikes and equipment resets that harm the pile.
• Pressure to decarbonise is encouraging a shift toward more efficient systems, renewable energy integration and better building envelopes.

In practice, storage operators are being forced to think about:

• efficiency – upgrading fans, motors and controls to get more cooling and airflow per kilowatt-hour,
• load management – running hardest when energy is cheaper or more available, and coasting intelligently at other times without compromising the crop,
• backup – generators, batteries or dual-fuel solutions that keep critical systems running during outages.

A great pile can be lost in a single prolonged power cut if there is no fallback. Risk planning now needs to include the question: what happens in this store if the power goes off for six hours in the wrong weather?

Disease in the dark: when problems surface late

Many storage diseases develop slowly and only become obvious when it is almost too late.

• Fusarium dry rot often begins at wounds and spreads through the pile, slowly hollowing out tubers and leaving dusty, sunken lesions.
• Silver scurf develops on skins, intensifying over time and making tubers look aged and dehydrated, particularly in fresh markets.
• Soft rots driven by bacteria can turn small pockets of the pile into foul-smelling, liquefied masses that contaminate neighbouring tubers.
• Pink rot and late blight can follow tubers into storage from infected fields and continue their work quietly under the right conditions.

Two things are consistently present in serious disease breakdowns:

• an initial source of inoculum – diseased tubers, soil, vines, dirty equipment, contaminated bins or boxes,
• and storage conditions that favour spread – warm pockets, free moisture, poor airflow, weak hygiene.

Reducing storage disease pressure therefore requires:

• careful grading or at least removal of obviously diseased tubers before long-term storage,
• strict cleaning and disinfection of equipment, boxes, bins and building surfaces between seasons,
• attention to cull pile and waste management so that infected material does not remain as a reservoir near intakes,
• and temperature and humidity control that keeps the environment hostile to pathogens without damaging the crop.

The goal is not sterility – that is impossible in a commercial store – but a strong bias against disease development.

People, routines and the “boring” discipline that saves crops

Storage technology has advanced, but one thing has not changed: the people running the store matter as much as the hardware.

Many high-performing operations share common traits:

• written protocols for the first days after filling, including target temperatures, humidity and airflow,
• clear responsibilities – someone who is really in charge of the pile, rather than a vague shared responsibility that can fall through the cracks,
• regular walk-throughs and checks – listening to fans, looking for condensation, sniffing for early signs of rot, checking temperature readings against reality,
• a culture where reporting a “small problem” early is encouraged rather than punished.

On the other side, many storage disasters have a familiar pattern:

• assumptions that everything is fine because alarms are not ringing,
• delayed reaction to early warning signs – a small hotspot, a patch of condensation, an odd smell, slightly soft samples,
• overconfidence in automation – assuming that once the system is set up, it will keep running correctly without oversight.

The human factor is often underestimated in storage risk discussions. Yet decisions made at midnight, under time pressure, by tired people determine whether the pile stays quiet – or starts to slip.

Designing stores for a harsher world

As climate volatility and market demands increase, new builds and major refurbishments are being pushed toward more resilient designs.

Key trends include:

• better insulation and tighter building envelopes to reduce energy demand and improve temperature stability,
• flexible ventilation that can mix outside and inside air in more nuanced ways, rather than simple “on/off” intake,
• zoned stores where different crops or risk levels can be managed separately, rather than one big undifferentiated space,
• integrated monitoring – tuber probes, air sensors, pressure measurement, energy metering – feeding into single control platforms,
• and design features that make hygiene practical: washable surfaces, easy access for cleaning, well-thought-out waste handling.

Good storage design is not cheap. But as seasons become more extreme, the cost of under-spec’d stores is showing up in breakdown losses, energy bills and lost flexibility.

Joining the dots: from field plan to storage strategy

Perhaps the biggest shift needed is mindset: treating field and storage as one system, not two separate worlds.

That means planning:

• which fields will fill which stores based on disease risk, soil type, harvest timing and target market,
• how many “high-risk” lots the system can realistically cope with before stress becomes unmanageable,
• what mix of varieties and dormancy characteristics is going into each space,
• and how long each lot is expected to stay – whether it is moving quickly or expected to sit for months.

Integrated planning reduces nasty surprises. It allows a manager to say, for example:

• This store can handle some hot, bruised, early-lifted crop – but then it cannot also be loaded with late-lifted, disease-prone material without serious risk., or
• These two lower-risk lots can go into a simpler building with lower control – this high-value, high-risk lot must go into the best-insulated, best-controlled store.

In a world of tight margins, that kind of planning is easy to skip. But it is exactly what turns storage from a passive cost centre into an active risk-management tool.

When it goes wrong – and what can be learned

Stories circulate quietly in every region:

• piles that liquefied after a power cut and a week of wishful thinking,
• stores that were overloaded “just this once” and later plagued by chronic hotspots,
• energy-saving experiments that pushed temperatures too high, triggering sprouting or sugar accumulation,
• well-intended curing regimes that turned into incubators for disease.

The common thread is not incompetence. It is the mismatch between a living, changing pile and systems – technical and human – that were too rigid, too slow or too stretched.

Every failure, painful as it is, contains information:

• Did the problem start in the field or in the store?
• Were the warning signs visible earlier?
• Did the design of the building and kit help or hinder the response?
• What would have had to be different in planning, operation or communication for the outcome to change?

In a harsher climate, those lessons are expensive not to learn.

Storage as a quiet form of resilience

When people talk about resilience in the potato industry, they often reach for big topics – breeding, irrigation, soil health, disease pressure. Storage rarely leads the list.

Yet storage is one of the most concrete, controllable ways to turn a vulnerable crop into a more resilient business. A good storage system:

• cushions the impact of bad harvest weather by reducing losses,
• spreads market risk by allowing sales over a longer window,
• and gives growers and buyers time to make decisions based on price and demand, not panic.

The opposite is also true. Weak storage turns climate shocks into crises, forces distress selling and undermines trust all along the chain.

In the years ahead, as seasons grow more erratic and energy and market volatility remain high, the quiet work done inside the pile will matter more, not less. Those who treat storage as a strategic asset – designed, managed and staffed with that mindset – will find that a good crop is only the beginning of a successful season, not the whole story.

Author: Lukie Pieterse, Potato News Today
Image: Credit Potato News Today