Holding the ground: Why soil retention is becoming a potato production priority

Potato production can lose soil through runoff, wind and harvesting itself. The cost is measured in fertility, water, compliance—and the future usefulness of the field.

By Lukie Pieterse, Editor/Publisher of Potato News Today

In June 2025, an English potato grower appeared in court over an incident that had occurred almost three years earlier. Following thunderstorms in Somerset, potatoes and silt were washed from a sloping field, closing a public road and polluting a nearby watercourse.

The UK Environment Agency estimated that between 50 and 100 tonnes of soil left the field. Court penalties, compensation, clean-up expenses and remedial work reportedly cost the business more than £40,000.

It would be easy to treat this as an isolated enforcement story. That would miss the more useful lesson.

Potatoes are grown in loose, intensively cultivated soil, often on shaped beds or ridges that remain only partly protected until the canopy closes. Harvest disturbs the field again and may leave little vegetation during a season of heavy rain or strong wind. The crop therefore presents a structural challenge: growers must create the friable soil needed for tuber development without creating a field that is ready to move.

Most losses will never close a road or reach a courtroom. They occur gradually—soil collecting at the bottom of a slope, blowing from a dry seedbed, leaving through drains, or travelling to the store and factory with the harvested crop.

Because the process is dispersed, the industry can underestimate its scale. Yet the soil leaving a potato field carries fertility, organic matter, water-holding capacity and part of the field’s future earning power with it.

Why potatoes expose the soil

A potato crop requires a particular physical environment. Compacted or cloddy ground restricts rooting, interferes with tuber shape and complicates harvesting. Growers therefore invest heavily in cultivation, destoning, bed preparation and ridge formation.

These operations create productive conditions around the developing tubers. They can also break stable aggregates into smaller particles that are more easily moved by water or wind.

The crop provides relatively little early-season protection. Rain can strike bare soil directly before the canopy develops, while water moving along furrows may gather speed and volume. Wheelings, compacted headlands and smeared layers reduce infiltration and direct more water across the surface.

After harvest, the protective canopy disappears immediately. The lifting process breaks and exposes the soil once again, frequently at the beginning of a wetter or windier period.

The risk is not uniform. Soil texture, slope, rainfall intensity, irrigation, organic matter, field shape, cultivation direction and the condition of neighbouring land all affect the outcome. A practice that works on a nearly level loam may be inadequate on lighter soil above a watercourse.

This is why erosion control cannot be reduced to a standard product or a box on an assurance form. It begins with understanding how water and soil are likely to move through a particular field.

Water does not respect the field boundary

The Somerset case attracted attention because the consequences became visible beyond the farm. According to the Environment Agency’s account, most of the potatoes had been planted up and down the slope. Under severe rainfall, the rows provided a route for runoff towards the road and stream.

Planting across a slope, working nearer the contour, interrupting long runs and maintaining vegetated margins can slow that movement. But none is automatically safe. Contour systems need suitable outlets, while poorly planned ridges can concentrate water until they fail.

Scottish Farm Advisory Service guidance recommends treating slope, soil condition and field layout as connected decisions. It describes the use of tied ridges or small depressions between rows to retain water and encourage infiltration, as well as grassed headlands and margins that can intercept sediment.

Such measures have to be matched to local rainfall, machinery and soil. Retaining water within a ridge is helpful only while the soil can absorb it and the structure remains intact.

Irrigation deserves the same scrutiny. An application rate that exceeds the soil’s infiltration capacity can create runoff even on a day without rain. A compacted wheeling may carry that water far beyond the irrigated area.

The important question is therefore not simply how much water entered the field, but where it went after arriving.

Some soil departs through the harvester

Water and wind erosion are familiar concepts. Less visible is soil loss caused by crop harvesting.

Soil adheres to tubers, becomes trapped in clods or is carried through trailers with the crop. Researchers describe this as soil loss due to crop harvesting. It occurs in root and tuber crops worldwide, although reported quantities differ greatly according to soil type, moisture, machinery, crop condition and the effectiveness of field separation.

A study of smallholder potato systems in Tanzania’s Western Usambara Mountains estimated an average loss of about 0.7 tonnes of soil per hectare per harvest. Earlier mechanised research in Belgium reported a considerably higher average, with very wide variation between fields.

The numbers should not be transferred casually from one production system to another. Their importance lies in showing that harvesting can remove measurable soil even when no erosion channel is visible.

Wet lifting conditions generally increase the amount of soil attached to tubers and clods. They may also increase bruising risk, reduce separation efficiency and raise the cost of transporting material that has no market value.

Soil arriving at a packhouse or processing plant creates another problem: what should happen to it?

Returning it to farmland may appear sensible, but soil can carry potato cyst nematodes, volunteer tubers, weed seeds and soil-borne pathogens. Moving it between farms or fields may spread the very organisms that seed and hygiene systems are designed to contain. Disposal or return must therefore follow local plant-health and waste rules rather than an assumption that all soil should simply go back to the land.

A useful starting point would be to measure soil tare more consistently. Where large amounts repeatedly arrive with the crop, the figure is not only a factory-handling issue. It may reveal something about harvest timing, clod formation, machinery setup or the condition in which the field was lifted.

The commercial loss continues after the storm

Erosion is often presented as an environmental concern, which it certainly is. Sediment can damage streams, carry nutrients and crop-protection products, block drainage systems and impose clean-up costs on communities.

But the loss also belongs in the farm accounts.

The most fertile part of the profile is generally concentrated near the surface. When that soil moves, the field loses organic carbon and nutrients along with fine mineral particles. The remaining ground may store less water, infiltrate rainfall more slowly and become harder to cultivate.

The effect can be self-reinforcing. Reduced infiltration produces more runoff; poor structure encourages more aggressive cultivation; aggressive cultivation leaves the soil more vulnerable to the next event.

Off-site incidents bring additional exposure. Roads may need cleaning, drains can become blocked, water pollution can trigger enforcement and relationships with neighbours or landowners may suffer. On rented ground, responsibility can become especially contentious if the cropping decision, field condition and remedial costs fall on different parties.

Soil protection is therefore not merely about preserving an abstract resource for a distant future. It protects the ability to crop the field commercially next season.

Field choice may be the strongest control

Some fields are unsuitable for potatoes in a particular year, even if they are capable of producing an attractive crop under ideal conditions.

A meaningful field-risk assessment should consider slope length and direction, soil texture, compaction, previous cropping, nearby roads and houses, watercourses, drainage outlets and the consequences of an unusually intense storm. It should also consider what will follow the potato crop and how quickly protective cover can be established.

That assessment needs to take place before land is rented, contracts are finalised and the planter enters the field. By then, many of the most effective options have already disappeared.

The issue is larger than the grower. Landowners should understand how a high-risk crop will be managed. Contractors need clear instructions about cultivation direction, wheelings and headlands. Buyers can influence risk through delivery periods, variety specifications and pressure to harvest when soil conditions are poor.

If the supply chain expects growers to protect soil, it must also recognise the commercial decisions that make protection difficult.

Cover crops can help—but timing decides whether they exist

One of the most promising interventions is rapid establishment of vegetation after harvest.

Research in eastern Canada found that winter cover crops planted after early-harvested potatoes reduced erosion by as much as 59%. The finding is highlighted in a recent Soil Health Institute discussion of resilient potato production.

That result should encourage experimentation, but not indiscriminate prescription.

In short northern seasons, a crop drilled after a late potato harvest may establish too slowly to provide meaningful protection. Species must suit the sowing date, temperature, moisture, following crop and pest-management plan. A cover that hosts an important nematode or complicates spring fieldwork can exchange one problem for another.

Canadian research led by Agriculture and Agri-Food Canada has shown that cover-crop benefits depend strongly on species and position in the rotation. Its work found useful effects from high-residue crops such as pearl millet and sorghum-Sudan grass when grown before potatoes, including improvements in yield and reductions in root-lesion nematodes under the studied conditions.

Where post-harvest establishment is unreliable, researchers are also investigating interseeding covers into the standing potato crop. University of Maine guidance explains the potential advantage: the cover has time to establish before lifting and can begin protecting the soil as the commercial crop leaves.

The difficulty is competition. Species, placement and sowing date must be managed so that the cover does not interfere with the potato crop, weed control or harvest. Interseeding is a promising tool, not yet a universal answer.

The best plan combines barriers

No single measure will make a vulnerable field safe under every storm.

Protection comes from layers: selecting appropriate fields, maintaining organic matter, limiting compaction, aligning rows sensibly, interrupting runoff pathways, retaining grassed margins, matching irrigation rates to infiltration and establishing cover as quickly as conditions allow.

Harvest management belongs in the same plan. Waiting for suitable soil moisture can reduce clods, tare and structural damage, although growers working under weather and delivery pressure do not always have that luxury.

This is precisely why the plan should be written before the pressure arrives. It should identify high-risk areas, responsibilities, emergency actions and circumstances in which planting or harvesting must be reconsidered.

Records can remain practical. Photographs after heavy rainfall, notes on sediment movement, soil-tare figures, infiltration observations and maps of repeated problem areas may reveal more than an expensive monitoring system used without a clear question.

The purpose is not to prove that no soil particle ever moved. It is to find where avoidable losses occur and reduce them season by season.

The crop must not take the field with it

Potato growers are expected to produce uniform tubers from a soil environment that must be loose enough for growth, strong enough to carry machinery and stable enough to withstand weather. That is a difficult physical balance, made harder by more intense rainfall, narrow harvest windows and commercial pressure.

The answer is not to retreat from potato production. It is to recognise soil retention as one of its central production disciplines.

We measure tonnes of potatoes leaving the field with considerable precision. We pay much less attention to the tonnes of soil that sometimes leave beside them.

That accounting needs to change.

Soil lost in a single storm may take decades to rebuild. Soil carried to a factory may become a handling cost or a biosecurity risk. Soil deposited on a road or in a stream can turn a field problem into a public one.

The field is not simply a platform on which the crop is produced. It is productive capital—and unlike machinery, it cannot readily be replaced when it is worn out or washed away.

A successful potato harvest should remove the crop while leaving the field capable of producing another. That may be the simplest definition of sustainable production the industry has.