Tuesday, 12 September 2017

Electra – sturdy but responsive: The story from SPot South West at Dillington Farms.

Read the latest blog from SPot South West by Knowledge Exchange Manager, Anne Stone.

Electra is a reliable high yielder that stores well, which is why many growers in the South West are attached to the variety.

It has good resistance to bruising, late blight on foliage, common scab and several other skin diseases. It’s also sensitive, responding quickly to quite small applications of nitrogen fertiliser.

However, there is one problem. Some Electra arrives at the pack house with low dry matter, and there’s not much enjoyment in the meal when that product comes to the table.

Branston Ltd didn’t take long to track those low dry matter consignments back to fields that had been generously fertilised with nitrogen. In 2016, they collected evidence by careful measurement of crops from 51 fields, which showed a clear correlation of nitrogen fertiliser with tuber dry matter.

SPot Farm South West at Dilington
AHDB’s Strategic Potato farm (SPot) programme looks for specific questions linked to its more general themes of research, which can be applied to a commercial farm.
Dillington Estates thought that determining what irrigation and nitrogen rates give reliably high tuber dry matters without reducing yield, was a topic worth tackling.

                       Chris Wilson, Dillington Estates Director, speaking to some of the visitors on August 23rd.

Branston visit
On August 23, Branston Ltd organised for its suppliers to visit SPot South West, which included a look at Joe-S field just before burn-down.
There was no doubt about the response of haulm length to nitrogen rate, as shown in the photos below, where Ben Mitchell of Branston Ltd provides the scale.

Marc Allison of NIAB CUF put the field comparison into context.  Marc explained that, in general the factors determining tuber dry matter are variety, irrigation and season. Whereas nitrogen fertilisation is of lesser importance. However, dry matter is more sensitive to nitrogen rate in some varieties than in others, and Electra is certainly sensitive. Marc thought that from the look of the crops under the three nitrogen treatments, 90kg/ha was the best one in this particular case, though yield and final quality results are still to come.

When samples were measured in mid-August the average dry matter at 150kg/ha N was 15.5%, rising to 16% at 120kg/ha and 17.1% at 90kg/ha.

Following his talk, there were many interesting questions:  Here’s a selection, with a summary of Marc Allison’s replies.

Question - is it OK to apply all the nitrogen pre-planting?
Answer. Yes, is usually is good to do so. Only where there is a high risk of leaching would top dressing be desirable.
Question – Is placement of nitrogen and phosphate, rather than broadcasting, worthwhile?
Answer. Placement generally has no effect.
Question – What’s the effect of different forms of potash?
Answer. Research indicates that muriate can reduce tuber dry matter. But it’s a weak effect and only applies when quantities are large.
Question – I don’t have irrigation. Can using extra nitrogen help a crop through a dry spell?
Answer – Yes, but its variety dependent. This effect mainly applies to determinate varieties.

Results. We look forward to further data from Joe-S field, to be revealed at the Results Day on November 28th.

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