The recent national potato conference was told that the trend for falling potato consumption has turned and is on the up once again. This was welcome news for a sector whose fresh product was being shunned in favour of more convenient and possibly less healthy carbohydrate alternatives.

Cliona Lynch from Kantar Worldpanel told the meeting that consumer sentiment is back to pre-recession levels and that potato consumption is rising also.

Consumers are buying more fresh foods and this includes potatoes. Under-25s are now buying more potatoes, which is helping consumption and developing a trend for the future. Consumption is now back to 2008 levels.

Chris Linsell from Kindrid spoke about the joint potato marketing campaign which ran in Ireland and the UK in recent years. The €4.6m campaign was funded by growers and industry and was 50% co-funded by the EU.

The campaign targeted simple messages and encouraged consumption by generating appeal for the spud and the creation of numerous simple recipes. The campaign coincided with a recovery in consumption but some suggest that this might have happened either way.

However, it is hard but to conclude from the presentations that the campaign did contribute significantly to the consumption lift.

Nutrition

Two morning sessions focused on the considerable nutritional benefits of potatoes. Dietitian Aoife Hearne, known from operation transformation, outlined the very many healthy characteristics of the potato, right down to the value.

Fibre and starch are essential constituents of our diet and potatoes, especially with their skins on, bring these in abundance. They may be a carbohydrate, but these are also essential Aoife said.

Fiona Crispie of Teagasc, Moorepark, outlined the benefits potatoes bring to the health of the human gut and the knock-on benefits that a healthy gut has for the whole body.

Research is now showing a greater diversity of microbes in the gut of athletes versus non-athletes and that there are different microbes present in both sets of people.

The increased fibre and protein consumption by athletes leads to the production of specific short-chain fatty acids which carry signals to the brain to help regulate mood, etc. And potatoes, with their high fibre and starch, are one of the key dietary constituents that help to do this.

Optimising storage

Storage remains a critically important part of potato production. The principles of storage have moved from ambient bulk storage to refrigerated box stores. The principles are now reasonably well understood, but it is still a challenge to get these perfectly executed in stores.

One presentation at the conference dealt with issues of store design and operation that affect air flow and hence local storage conditions within a store.

Adrian Cunnington is head of crop storage research at AHDB Sutton Bridge and he talked about a range of measures which can help optimise store performance.

Fan specification and operation is just one of these. He said that fan capacity should be sized for a worst-case scenario, but they should be fitted with inverters so they can also be operated at lower speeds to save on energy. Adrian said that if it costs €1 to operate a fan at full capacity, it will cost €0.50 to run it at 80% capacity.

The savings are important, but there are also times when slower speeds can be useful for other reasons, such as CIPC application. Recirculation within the store using slow-speed fans is an increasing requirement of CIPC application.

Adrian said that one of the current issues with CIPC registration is the very high levels found on some tubers, while others do not receive enough to prevent sprouting. This is very much an air circulation issue driven by the easiest return path for air to the point of recirculation.

It is extremely difficult to get uniform air flow into the top corners of a store nearest to the fridge units and this is where problems such as skin diseases or sprouting are most likely to occur.

Adrian referred to this phenomenon as the “coke bottle” effect and it can occur in both the horizontal and vertical planes (see diagrams).

This can be demonstrated in stores using air flow monitoring and modelling. Adrian said that measures such as fitting a curtain or mesh to alter the return path for air to force more through the boxes, rather than short-circuiting, can help greatly.

Fitting an engineered plenum to help control air movement can be even more useful at driving air direction. Other design features, such as forcing lateral suction through the boxes for positive ventilation, can also help overall air flow.

Ensuring that the coils and fins in the fridge unit are clean can greatly help efficiency. Having the capacity to measure energy usage in store is also very useful to help control running costs. The prevention of air leakage from the store is also important, as more air has to be cooled to compensate.

Finally, he suggested that humidification has potential to extend ambient air use and reduce weight loss in stores, especially in processing stores. But there is a real associated risk of condensation.

The threat of PCN

While we in Ireland have traditionally not had an issue with potato cyst nematode (PCN), it is appearing in more and more fields, according to Teagasc’s Shane Kennedy.

He described is as “a pest that requires your undivided attention”, as it is potentially lethal for the sector.

While many different nematode species occur naturally in the soil, only a few cause serious concern for plant production and PCN is one of these.

There are two species of PCN, Shane said, Globodera rostochiensis (yellow cyst nematode) and Globodera pallida (white cyst nematode). Nematode populations build on the roots of potato plants where they produce cysts which remain dormant in the soil until the next host crop arrives. There is a legacy effect following infestation and Shane said that eggs can remain in the soil for up to 25 years.

An EU directive forces the testing of all land used for seed potato production annually, plus 1% of land used for ware production. If land is found to be positive for PCN infestation, the landowner is issued with a prevention notice prohibiting the production of potatoes or other host crops for at least six years and then it must be retested.

Despite the limited sampling intensity, Shane reported that approximately 20% of the tested land was infested. Traditionally in Ireland the main problem had been G. rostochiensis, but test results from recent years are showing a significant level of G. pallida.

Shane said that this is a worrying trend because G. pallida has a longer hatching period, can survive lower temperatures, there is less genetic resistance available, has a slower rate of natural decline and nematicides are less effective.

It is possible to get good variety resistance to G. rostochiensis, but this is single-gene resistance and must be regarded as vulnerable over time. It is more difficult to develop good resistance to G. pallida because it is genetically more complex.

That said, if G. rostochiensis is the only issue, growing resistant varieties enables hatching of the eggs but prevents the completion of the life cycle and hence it helps to reduce the population. So resistant varieties can be used to clean up a field, providing only G. rostochiensis is present.

Tolerant varieties are also available. While these can grow well, Shane said that the nematode can still thrive and numbers will increase.

Rotation has traditionally been used as the main control mechanism for PCN. Normally, a five-year rotation was recommended, but modelling work is indicating that PCN can still manage to increase within this time scale.

Shane went on to report that field multiplication is still possible, even with a seven-year rotation. So rotation itself is not a cure for a problem.

Trap crops such as Solanum nigrum can help. These encourage the hatching of the eggs, but do not support the lifecycle and hence they reduce numbers. However, a gap year in the rotation may be required for these to work best – they need time.

Biofumigants also got a mention, but not enough is known yet. Nematicides are still an option. The most important element in the control of this pest is hygiene, Shane said. Movement of soil is the major risk and this can happen on machines, boxes and even vehicles.

In the workshop which followed, growers favoured tougher legislative controls to prevent the problem from developing. Once it gets into any land, it is extremely difficult to prevent its spread.

Salad potato husbandry

Over the past three years, Teagasc, in conjunction with the IFA and Bord Bia, have been examining the potential to grow salad potatoes in Ireland. The ability to produce this crop would mean import displacement plus another market. IFA figures estimate the total salad potato market to be 7% to 8% of the ware crop or up to 25,000t.

The project looked at all aspects of production from variety to seed rate, nutrition, protection, burning off and storage. Speaking at the conference, Teagasc’s Shay Phelan suggested that the project had helped to increase the area sown to salads from an estimated 148ha in 2015 to almost 220ha in 2017. He suggested this area increase could continue.

Expert adviser to the project Stuart Wale, of the SRUC in Scotland, described salad potatoes as a highly specialised crop, with an absolute necessity for the quality the market demands. The crop requires even higher attention to detail than a standard crop, but little in the way of additional production equipment.

Field selection is critical, Stuart stated. That means a uniform, workable, free-draining soil for a good skin finish. Availability of irrigation is critical.

Seeding rate is also very important. Narrow seed bands are essential and split grading is often used to keep seed within a 5mm band. The size of the seed band is not so important, but it has to be tightly graded. Uniformity of emergence is important with such a high plant population.

Good nutrition is essential. Ensure phosphate application is appropriate to encourage tuber formation. Nitrogen rate should be influenced by variety, but do not over-apply.

Skin finish is paramount, so irrigation is essential to help prevent common scab. Irrigation is also important to prevent large soil moisture deficits during tuber formation.

The susceptibility of most salad varieties to blight means that good blight control is essential and this should continue up to post-haulm destruction.

Tuber size is critical and so timely burning off or haulm destruction is critical. Stuart stated that test digs are essential every two days during the critical period and advised haulm destruction when the largest tubers are at the top riddle size. This is very important, as additional tuber growth will occur post-initial haulm destruction.

Given the importance of skin finish, it is essential that tubers be well dried down prior to going into store. They should then be cooled and put into storage at a target temperature of 2°C to 3°C.

Ed Tobin from Slaney Farms in Enniscorthy was the grower at the centre of the project. He emphasised that this is a more demanding crop than ware. Issues such as seed require more precision, he said. They split grade the seed and operate on a figure of approximately 1,000 tubers per 50kg. Planting speed is kept slow to help accurate seed spacing.

Rapid establishment and early growth are important. Ed applies 100kg P/ha at planting plus a few follow-up foliar sprays of phosphorous plus magnesium with the early blight sprays. He sees early blight control as very important because of the density of the canopy.

Irrigation is so important that he has to be prepared to pull the equipment off of a ware crop to irrigate the salads at critical times. Ed reiterated the need for test digs every two days to guide haulm destruction. Harvest is also critical, in that he is trying to get the soil sufficiently moist but yet adequately dry.

Ed said that his yields for the past three years have averaged around 16t/ac to 17t/ac and that Gemson is currently his variety of choice.