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Potato yields in the UK:

'Can we harvest 100 tons per hectare?'

Potato yields in the UK appear to be faltering and one expert believes a yield competition like that seen with wheat could help the sector get closer to three-digit yield figures. Yield data from the AHDB suggest there has been a slowing down in the rate of increase in yields. This is in contrast to -for instance- the sugar beet sector, which is still seeing a strong upward trend.

While AHDB figures show the 2018 potato crop averaged 41.7t/ha, NIAB CUF head David Firman points to the huge variation between crops, with some yielding above 80t/ha. Washington state in the US is a standout performer, with an average above 70t/ha.

And triple-digit yields have already been seen in the UK. An irrigation trial in 2013 achieved 125t/ha with the variety Volare, although this was somewhat at the expense of dry matter content.

Dr Firman believes the more impressive performance was for a 114t/ha crop in a Washington State University variety trial, equating to a dry matter yield of 26t/ha: “It shows that there is an opportunity to increase yields considerably.”

There are different factors that can hold back yields:

Dr Firman picks soil physical conditions as the top contender, as some of the biggest yield differences have been seen in trials comparing compacted and uncompacted soils. Compaction is a particular problem for potatoes because of the impact on root development.

Firman believes another key factor is irrigation, as a substantial proportion of the UK area is not irrigated. The latest AHDB survey shows only 53% of the land in Great Britain planted with potatoes in 2018 had access to irrigation. He points to reference crop trials, which over the years have shown a potential loss of more than 10t/ha without irrigation, and sometimes higher in more extreme seasons.

Market requirements
Another possible factor is the drive for market specifications, as growers focus on tuber size and dry matter content. For salad crops, farmers grow tubers until they reach a size specification, so the crop is not allowed to reach its maximum yield.

Similarly, processing crops, which account for 29% of the total area, are grown for a higher dry matter content because of fry quality, which has an impact on fresh weight yield. A good illustration of how the different market sectors can distort figures is when looking at regional yields – with Scotland down the regional rankings.

Variety may also be a factor, with older varieties accounting for a big proportion of the area at the expense of newer, higher-yielding ones. For example, Maris Piper is still the most widely grown variety, having been around since the mid-1960s. Another example of varietal effects is seen with rooting, with Estima giving bigger yield responses to irrigation compared with Cara. Dr Firman suggests this is because Cara has a bigger root system, helping it cope better in dry conditions.

Loss of pesticides
The continued loss of pesticides could also be holding yields back, and the recent loss of diquat is not going to help. There is a perception that there is a worsening potato cyst nematode problem in Britain, but Dr Firman points to data from the most recent PCN survey suggesting this is not the case.

Bayer biopesticide expert Tim Lacey says Serenade is a particular strain of Bacillus subtilis that has been shown to help fight soil pathogens and promote root health.


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