By Lukie Pieterse, Editor/Publisher of Potato News Today
New research from Europe and North America is challenging a deceptively simple assumption about potatoes and water. More irrigation does not always mean more marketable crop — and products promising greater drought resilience do not necessarily protect yield. As water becomes less predictable, the real opportunity may lie in much more precise decisions about when, where and how much to irrigate.
For a potato grower watching a crop begin to suffer from lack of water, the obvious response is difficult to argue with: irrigate.
But what if the more important question is no longer simply whether to irrigate?
What if it is when, how much, by what method — and on which variety?
A series of research findings published during the past two years, including several in 2026, is beginning to sharpen that question.
The studies come from very different potato environments: semi-arid Morocco, greenhouse experiments in Denmark and the Czech Republic, irrigated processing country in Washington State, and the traditionally humid potato fields of Prince Edward Island in Canada.
Their results are not uniform. That is precisely why they are interesting.
They suggest there may be no universal “water-saving technology” for potatoes. Instead, the emerging lesson is that crop stage, cultivar, soil, irrigation system, climate and the economics of the harvested crop all influence whether reducing water becomes clever management or an expensive mistake.
A 12% saving in Morocco — without a significant yield penalty
Researchers working under semi-arid Mediterranean conditions in Morocco recently examined several approaches to reducing the water requirement of potato production, including regulated deficit irrigation, subsurface drip irrigation and straw mulching.
The results, published in Potato Research in 2026, are worth examining carefully.
Regulated deficit irrigation saved approximately 12% of irrigation water without causing a statistically significant yield penalty. That sounds straightforwardly encouraging. The rest of the study makes the picture more complicated.
The researchers did not find a significant improvement in irrigation water-use efficiency from that treatment. The water saving was relatively modest, and there was also a small, although statistically non-significant, reduction in yield.
Subsurface drip irrigation produced another intriguing result. Instead of keeping irrigation water near the soil surface, buried drip lines encouraged a distinctly different rooting pattern. Researchers observed stronger roots extending deeper into the soil and fine-root development around the underground wetting zone. Later in the season, plants under subsurface drip irrigation showed advantages in development, although the researchers themselves cautioned against overinterpreting some of the individual-plant yield observations.
Straw mulch, meanwhile, failed to produce the expected yield benefit in this particular experiment. That negative result deserves almost as much attention as the positive ones.
Agriculture has no shortage of practices described as “water-saving”. Their performance depends heavily on where and how they are used.
The timing of water may matter almost as much as the amount
Research conducted near Othello in Washington State offers another useful piece of the puzzle.
Across three seasons, researchers tested five late-season irrigation levels — from 40% to 120% of modelled evapotranspiration — on Alturas, Clearwater Russet, Ranger Russet, Russet Burbank and Umatilla Russet. The irrigation treatments began around peak canopy growth and continued until vine kill. The results demonstrate why simple prescriptions can be dangerous.
Reducing late-season irrigation generally reduced total yield as the cuts became more severe. But the response varied considerably among cultivars. For Alturas and Umatilla Russet, reducing irrigation by 20% from the 100% evapotranspiration treatment did not produce a statistically significant reduction in total yield.
For Alturas, the 20% reduction increased crop water productivity by about 8%. Applying more water did not automatically help.
Irrigation at 120% of the modelled evapotranspiration requirement produced no significant total-yield benefit, while crop water productivity declined by about 10% for Alturas and Umatilla Russet compared with the 100% treatment.
There was another complication.
Some quality measurements actually improved when late-season water was reduced. Alturas, Russet Burbank and Umatilla Russet recorded increases in the proportion of US No. 1 tubers under certain reduced-irrigation treatments. Clearwater Russet and Ranger Russet responded differently.
So the question becomes more interesting than “How much water produces the greatest yield?”
Growers are not paid simply for biological tonnes.
They are paid for potatoes of the right size, shape, specific gravity, processing characteristics and market specification.
The economically optimum irrigation strategy may therefore differ from the irrigation strategy that produces the maximum physical yield.
More water is not insurance
This may be the most practically important point emerging from the research.
Potatoes are highly sensitive to water stress, particularly during critical stages of tuber initiation and bulking. Severe deficits can quickly reduce marketable yield and quality.
But that does not make over-irrigation a sensible insurance policy.
Excess water can carry its own costs: energy, nutrient movement, disease risk, soil conditions and simply the cost of pumping water that generates no additional saleable crop.
The Washington work provides a particularly clear example. Increasing late-season irrigation from 100% to 120% of estimated evapotranspiration failed to produce a statistically significant increase in total yield across the cultivars examined.
There is an important distinction here.
Water security and high water use are not the same thing.
The objective is increasingly to ensure that the crop has sufficient water when water matters most — rather than assuming that maintaining the wettest possible root zone throughout the season is automatically safer.
Even rainy potato regions are reconsidering irrigation
That argument is no longer confined to traditional irrigated production areas. Prince Edward Island offers a particularly interesting case.
The Canadian province has historically relied heavily on rainfall for potato production. Yet researchers conducting on-farm experiments between 2019 and 2022 found that supplemental irrigation could reduce year-to-year variation in potato yields.
The important word is could.
In the dry seasons of 2019 and 2020, supplemental irrigation significantly improved marketable yields. During 2021 and 2022, when rainfall was better distributed, little irrigation was needed and yield responses were negligible.
The economic analysis was equally revealing. Supplemental irrigation was not automatically profitable. Its financial performance depended on equipment costs, the water-supply system, operating costs, field scale and — most unpredictably — rainfall itself.
This makes supplemental irrigation less like a conventional production input and more like a form of risk-management infrastructure.
In a dry year, its value can be substantial. In a wet year, expensive irrigation equipment can spend much of the season doing very little.
That calculation is likely to become relevant in more traditionally rainfed potato regions as rainfall patterns become less dependable.
Can biostimulants make potatoes more drought-tolerant?
This is where the story becomes considerably more contentious.
A growing market has developed around biostimulants and biological products promoted for improved stress tolerance, nutrient efficiency, root development and crop resilience. Some products undoubtedly produce measurable plant responses.
But does that mean they preserve potato yield during drought?
A study published in Frontiers in Plant Science in July 2026 offers a useful warning against making that leap too quickly.
Researchers associated with Aarhus University in Denmark evaluated five commercial biostimulants — Vesta, Humifirst, Acadian, SilicaPower and Crop-Set — using the potato variety Arielle.
Plants were grown in pots under controlled greenhouse conditions. At tuber initiation, half were subjected to seven days without irrigation, while the other plants remained watered.
Several biostimulants produced interesting physiological responses.
Under drought, Vesta, Humifirst and SilicaPower improved measurements of water-use efficiency compared with untreated plants. Some treatments also influenced tuber dry matter, starch or sugar composition.
But drought still reduced tuber yield by 26%.
And critically, the biostimulant treatments did not produce a statistically significant improvement in tuber yield.
The researchers’ interpretation is unusually useful because it resists the temptation to oversell their own results.
They concluded that the treatments appeared mainly to influence resource-use efficiency and metabolic responses rather than demonstrating broad drought tolerance. They also emphasised that biostimulant responses are context dependent, affected by factors including soil, climate, formulation and application method.
There is an important commercial lesson in that distinction.
A product can alter plant physiology without necessarily putting more marketable potatoes into a grower’s storage.
That does not make the physiological effect meaningless.
But neither should improved leaf-level water-use efficiency automatically be translated into a claim of improved field-scale drought resilience.
Field trials, multiple environments and economic data remain essential.
Variety may be an underappreciated part of water management
Another 2026 study raises an equally interesting question: have breeders unintentionally gained — or perhaps lost — drought resilience while selecting potatoes for modern yield and quality characteristics?
Researchers in the Czech Republic compared two modern cultivars, Adéla and Karo, with four older cultivars: Blaník, Bojar, Krasava and Norma. Drought significantly affected yield and tuber composition, but cultivar responses differed.
Bojar and Krasava did not experience statistically significant reductions in marketable tuber weight under the experimental drought treatment, while several other cultivars did. Yet the researchers could not conclude that the older group as a whole was more drought resistant than the modern cultivars. (Potato Research)
Again, the absence of a simple answer is valuable.
“Old varieties are tougher” would make an attractive headline. The evidence did not support it.
What it did support was substantial cultivar-to-cultivar variation.
That points toward an increasingly important breeding objective: water response should perhaps be considered not merely as a general attribute of potatoes but as a measurable varietal characteristic, alongside maturity, marketable yield, specific gravity, disease resistance and processing quality.
The Washington irrigation research reaches a similar conclusion from a completely different direction. Five processing cultivars responded differently to precisely the same irrigation regimes.
Water management and genetics cannot always be separated.
The next irrigation system may be a decision system
Much of the technological discussion around irrigation still concentrates on hardware: pivots, drip lines, pumps, sensors and variable-rate equipment.
Those technologies matter. But the research suggests that the more profound change may be happening in decision-making.
The useful question is no longer:
Does this field need irrigation?
It is becoming:
What does this cultivar need, in this soil, at this growth stage, under the current evaporative demand, given the quality specification and economic value of the crop?
That requires information.
Soil-moisture sensors, weather stations, evapotranspiration models, canopy measurements, remote sensing and increasingly automated irrigation systems are valuable not because they are impressive technologies, but because they can reduce uncertainty around that decision.
The ultimate objective is not minimal water use. Nor is it maximum water use.
It is economically productive water use.
That distinction matters.
A crop producing 50 tonnes per hectare with less water is not necessarily more profitable if tuber size or processing quality suffers. Equally, a crop receiving another irrigation pass is not more productive if the additional water produces no additional marketable value.
A different way of thinking about drought resilience
There is a tendency in agriculture to search for single answers to complicated stresses.
A drought-tolerant variety.
A biostimulant.
A new irrigation system.
A soil amendment.
A better sensor.
Each may have a role.
The evidence emerging from potato research suggests that resilience is more likely to come from combinations.
A cultivar that responds favourably to carefully timed deficit irrigation. A rooting environment that allows deeper exploitation of available moisture. Sensors that prevent both stress and unnecessary irrigation. Breeding programmes that treat water response as a selectable characteristic. Biological products that are required to demonstrate field performance rather than simply physiological activity.
And, perhaps most importantly, growers who have enough information to distinguish between a crop that genuinely needs another irrigation and one that does not.
The potato industry has spent decades learning how to produce more tonnes per hectare. The next efficiency frontier may be different.
In many potato regions, success will increasingly be measured not simply by how much crop a hectare produces, but by how much marketable value can be produced from every cubic metre of water available to it.
That is a considerably harder problem.
The research suggests it is also becoming one the industry can no longer avoid.
Sources consulted
- Asghar, M.A. et al. (2026). Comprehensive evaluation of biostimulants on leaf-level physiology, water use efficiency, and tuber quality in potato (Solanum tuberosum L.) under drought stress. Frontiers in Plant Science.
https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2026.1837304/full - Kretzschmar, H.A. et al. (2026). Enhancing Potato (Solanum tuberosum L.) Production in a Semi-arid Environment in Morocco Using Subsurface Drip Irrigation and Other Water-Saving Strategies. Potato Research.
https://link.springer.com/article/10.1007/s11540-025-09950-1 - Gonzalez T., F., Pavek, M.J., Knowles, N.R. et al. (2024). Reduced Late-Season Irrigation Improves Potato Quality, Often at the Expense of Yield and Economic Return. American Journal of Potato Research.
https://link.springer.com/article/10.1007/s12230-024-09948-4 - Jiang, Y. et al. (2024). Reducing Yearly Variation In Potato Tuber Yield Using Supplemental Irrigation. Potato Research.
https://link.springer.com/article/10.1007/s11540-024-09711-6 - Král, M. et al. (2026). Response of Old and Modern Potato Cultivars to Water Availability. Potato Research.
https://link.springer.com/article/10.1007/s11540-026-10051-w - Rai, A. et al. (2025). A scoping review of irrigation scheduling methods in potato production. American Journal of Potato Research.
https://link.springer.com/article/10.1007/s12230-025-09997-3
Discover more from Potato News Today
Subscribe to get the latest posts sent to your email.
