Research aims to break the potato yield plateau

An increasing disconnect between scientific advances and their practical application is being blamed for the lack of any large step changes in potato yields since the end of the Second World War.

That is despite the relentless amount of scientific research being published, which continues to grow, said NIAB CUF head of agronomy David Firman.

Since the mid-1990s, there has been a plateau in maincrop potato yields (see graph) at about 44.6t/ha, which can be attributed to many factors.

These include loss of soil fertility, a shift in market requirements to early and salad crops, increasing potato cyst nematode (PCN) levels on potato land and breeders focusing on traits other than yield.

“Keeping up with the vast scientific research is difficult and increasingly complex, and the adoption of advances can take a decade or more,” said Dr Firman.

This could be because growers may not be convinced of the benefits or it is not economic to put into practice.

It could also be because it is just too complicated to understand and implement, Dr Firman told delegates at the recent Cambridge University Potato Growers Research Association meeting.

“Moving on from the yield plateau is more likely to happen in small, incremental changes rather than the big step changes we have managed in the past,” he added.

The nature of the potato crop is also a problem when considering advances in production, particularly looking at plant physiology.

Dr Firman described the potato plant as very “plastic”, referring to its variability in the field due to its vegetative propagation and complex morphology (structure).

potato graph

This makes it challenging for researchers to identify improvements or responses to treatments in trials when looking for statistically significant differences in replicated trials, particularly in relation to yield. One way to improve this aspect of research is to increase replication.

However, resources need to be significantly larger to accommodate many replications of the same treatment and it limits the number of treatments that can be applied and assessed.

“We can instead change our experimental designs to accommodate a range of treatments to compare their main effects and combine series of experiments and their data,” he explained.

Future opportunities

An important recent scientific advance for potato production has been the mapping of the plant’s genome, published back in 2011 by an international team of scientists.

With this vital information, Dr Firman expects a rapid increase in the volume of published research aimed at understanding the complex interaction between the plant’s genetic code and how it performs in the field.

It could potentially provide the industry with considerable advances in new varieties and provide a better understanding of crop physiology.

However, translating those scientific advances into useful change at the farm level is more difficult and could take a considerable amount of time.

Breeders have found it difficult to introduce new potato varieties with significant market penetration, with the areas of the main commercial varieties remaining static for a number of years.

This is unlike the wheat industry, where despite the well-known yield plateauing, there are genetic improvements that provide a yield benefit, which result in shifts from older to newer varieties.

“Yield has not been such an important trait for the potato plant breeder and the difficulties with identifying high yielding varieties during the early stages of selection has also been a hindrance, said Dr Firman.

Unravelling mechanisms

The complex world of potato crop protection and nutrition – as well as genetics – will also present opportunities to improve production practices.

Understanding the mechanisms through which pests and diseases affect the crop and being able to affect those mechanisms to the advantage of the potato grower will be a key part of improving crop agronomy. There have been improvements in this area, with quality-robbing common scab and pests such as PCN.

Dr Firman said the improvement in common scab control for particular varieties after quantifying the soil moisture deficit (SMD) required to minimise its effect was a big step forward.

“New technology now allows us to monitor the pathogen that causes common scab and detect any changes in populations, which could allow us to offer more specific advice to growers in the future,” he said.

PCN populations are well understood in terms of their relationship with soil types and certain varieties, allowing advice to be given on control strategies.

However, as new varieties are introduced, experimental data will need to be gathered and fed into models, such as the Dutch Nemadecide system. This model predicts the expected population decline or increase and provides growers with targeted advice on PCN control strategies.

“It’s a big challenge, as the information required by models won’t be there straight away for every new variety that comes along and it will be costly to gather,” said Dr Firman.

Knowing your soils

In addition to crop protection opportunities, understanding of soil health and crop nutrition needs to be increased.

Quantifying what constitutes a fertile soil is still in its infancy and there are many aspects that remain unknown.

Current measures of fertility are based on soil chemistry – looking at the presence of the major nutrients. This can sometimes be irrelevant when considering yield potential of a particular field.

Ongoing NIAB CUF research is trying to understand the complex interactions that take place below ground level to provide advice on how to manage soils in an economically beneficial way.

“In terms of nitrogen, our understanding has gone beyond just applying a certain rate for a certain yield.

“Nitrogen for photosynthesis is relatively unimportant, but we have shown it has a great effect on the partitioning of dry matter in tubers,” explained Dr Firman.

As a result, growers should be producing the smallest canopy in the quickest time and only persist as long as it needs to, which is strongly influenced by nitrogen applications.

The advice on this aspect of crop nutrition will again vary across soil types and variety and Dr Firman said with pests and disease, constant crop monitoring and modelling will be required.

This would allow farmers to be given the most up-to-date advice for varying circumstances, guided by data collected year on year.

“We need to harness a combination of genetic and environmental resources [such as soils] and new technological advances to increase productivity.

“But there is also a need to bring together agronomic data from a wide and disparate number of sources, including from growers themselves in the field,” he said.

By scientists, growers and the wider industry working together, the sector would see yields increase, he said.

See more