Wednesday, 14 September 2016

'Scabby' findings and walking the tightrope at SPot Farm East

Welcome Back! 

I'm pleased to be able to report that we've had our final farm walk of the season at the Elveden Estate in what has been a brilliant first year at this site so far... and I thought it about time I got back on the blog to provide you with some interesting points of note!

But first, just to say, the efforts of the whole team involved in the programme have really generated a lot to talk about, alongside your inputs and interesting dialogue at each of the events - thank you for your critical part in the project!

Reporting on our final farm-walk then:

Visitors to the Elveden Estate’s last farm walk this season on September 1st saw how critical soil moisture can be to disease control... 

Control of common scab

Senior Farms Manager, Andrew Francis, has learned how to apply sufficient water at the right time to gain good control of common scab with a regime that works well, even for the highly susceptible Maris Piper! From tuber initiation, water is applied by boom when the soil moisture deficit in the top 30cm reaches about 12mm.

Some less susceptible varieties however, do not require as much water to protect against common scab, and having more knowledge on this topic is a great help when making decisions in circumstances where water has to be conserved.

We took a detailed look at irrigation for common scab control over at SPot Farm East this season in a demonstration planned by NIAB CUF. 

A field over at Summerpits was laid out so that a range of varieties were tested under various conditions: one set irrigated when the soil moisture deficit reached 10mm (moist treatment) and the other set when it reached 20mm (dry treatment).

Despite our best-laid plans, we're always at the mercy of the weather and 2016 proved not to be an ideal season in which to fine tune irrigation for common scab - rainfall kept the whole profile moist for much of June and in practice there was only one irrigation event extra in the moist treatment compared with the dry treatment and none of the varieties suffered more than tiny levels of common scab. 

However, the beauty of doing these demonstrations on real farm settings means you can reveal new information and findings that you weren't planning on originally!

We noted that this one additional irrigation event for the moist treatment set was associated with an effect on another disease: Powdery scab.

If you don’t fall off one side you’ll fall off the other!

Spongospora subterranea, which causes powdery scab, enters early in the season, around the same time as common scab. 

The majority of potato fields harbour the pathogen to some extent but this disease develops most severely in poorly drained soils. Our Powdery Scab Guide has oodles of extra useful information I won't be able to fully impart in this blog post today if you want to learn more.

...but back to those findings!

The soils at Elveden are very free draining, but that doesn’t make the crops safe in a wet year. 

The chart below shows data from the varieties which suffered noticeable powdery scab, followed up by some images of the variety Estima.

The top photo is of Estima from the moist treatment, while the bottom one is from the dry treatment.

This year’s results suggest that the line between having enough irrigation to control common scab and too much water which can provoke powdery scab is narrow, though it's also worth pointing out that powdery scab is a notorious for being a variable disease - it's possible the effect was due to a natural variability between the wet and dry areas regardless of the treatment applied.

Looking ahead to 2017... Attendees advise caution

At the end of the tour, we asked you who were there to talk to us about what you would like to see next year - and more specifically, which of the topics trialled in 2016 should be dropped for next year, and which new topics could hold potential for examination.

One grower wrote on his feedback form: “Replication of all trials is needed to compare different growing seasons”.

And certainly, many of the other attendees agreed that this topic of irrigation to control common scab in several varieties is something that needs to be looked at again next year.

If you didn't make it to this last farm walk, don't panic - there's still time before our steering group meeting in autumn to HAVE YOUR SAY on what we might practically demonstrate at SPot Farm East in 2017!

Pop your ideas on an email to me: - I'd love to hear from you!


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