Friday, 28 July 2017

Hard graft at SPot West

Read the latest blog from Heal Farms, Shropshire as Knowledge Exchange Manager, Anne Stone provides an update at SPot West.

At the field walk on 6 June the weather wasn’t on our side, it was a trek across the fields to reach the site. Listening to the speakers in the wind wasn’t easy, and a sharp squall sent everyone away fast at the end. Hopefully at the next event on August 17 the weather will be kinder, we can park in the field and enjoy a chat over a meal afterwards. 

Variety trial

At the field walk Dr Matt Back of Harper Adams University explained the difference between resistance and tolerance.

Tolerance refers to this season. A tolerant crop yields nearly as well in a PCN infested field as when there is no infestation. The mechanisms are not very well understood, but ability to replace nibbled roots may be one factor. Indeterminate varieties tend to be more tolerant.
Tolerance becomes visible during the season because tolerant varieties look much the same, with or without nematicide. Intolerant varieties develop a better canopy in nematicide treated plots.

Resistance refers to the future. A resistant crop stops PCN reproduction, so the egg numbers at the end of the season are less than at the start. The mechanism involves characteristics which stop the adult female getting plumbed into root vessels supplying water and nutrients. Resistance can’t be seen, we can only assess it at the end of the season when PCN eggs are counted.

The ideal variety is both resistant and tolerant, but few approach the ideal.

On 6 June there were no results to see, but by early July the differences between varieties were striking. For example; Performer and Eurostar are looking tolerant, with nematicide having little effect.

                                      Eurostar with nematicide                        Eurostar without nematicide

Royal, Arsenal, Alcander and Maris Piper all show a rather better canopy in the Nemathorin treated plots, suggesting some intolerance. 

                                    Maris Piper with nematicide                   Maris Piper without nematicide

Poor Maris Peer and Innovator are very intolerant indeed.

                                      Innovator with nematicide                      Innovator without nematicide

All the varieties are being tested to the limit, in this highly infested site.

Lodge 1 field has a lot of volunteer potatoes. Some emerged along with the crop, as shown in the picture below. More appeared later.

Volunteers in Arsenal, Lodge 1 field 1 June.

In 2013, Crisps4all was the variety in this field, but the farms director, Matthew Wallace, thinks these intruders look more like Saturna. Saturna probably beats its close rival VR 808 as the worst variety for ground-keeping. Both produce true seed as well as numerous very small tubers, with thick skins that seem to resist everything.

What problems get cures, and what problems don’t?
In human health, there have been amazingly effective treatments developed for stomach ulcers and worn out hips. Medicine has been less effective with bad backs and the common cold.  Agriculture has its own Cinderella subjects. Volunteer potatoes are one of the areas research finds hard to tackle. So many factors affect them, and they have so many effects, that its been a hard issue to investigate or cure.

Control of volunteers
Andrew Goodinson an agronomist with Agrovista, gave his advice:
  • In field preparation use a small web size on the de-stoner, so a similar web size can be used on the harvester, to reduce small tubers being returned to the field.
  • Use Amistar at planting to control Rhizoctonia.
  • Feed the crop correctly, with emphasis on phosphates and zinc, to prevent one big tuber developing.
  • Plant in good conditions since if cold and dry at planting a second flush of small tubers is more likely
  • Apply maleic hydrazide (Fazor) in 450l/ha water, five weeks before burn down. Apply by itself, not mixed with anything.
  • Crush small potatoes being returned to the field,(though Grimme no longer include such a crusher as standard)
  • Pre or post-harvest apply the highest rate of glyphosate which the label permits in the circumstances, with a wetter
  • In subsequent cereal crops use a sulfonylurea herbicide, then fluoxypyr (Starane) as late as possible to kill late emerging volunteers. Apply with a suitable nozzle to penetrate the cereal canopy
Expose the groundkeepers

Avoiding ploughing after potatoes exposes the remaining small tubers to frost in the first winter and to being eaten by birds and rodents.

Who ploughs?

Harry Henderson of AHDB Cereals and Oilseeds, sees a contrast between the East and West in cultivation after potatoes. Typically after potato harvest in September or early 
October the farmer in the East restructures the ground before wheat. The implement used has leading tines with wings, often followed by discs and a packer. There is a chance for potato tubers to drop behind the legs of the implement and be buried, but relatively few fall in this way. Restructuring is followed by a power harrow combination drill.

In the wetter West this approach can carry more risk. It is likely that the potato tramlines and those for wheat will be in the same direction. Restructuring will be done at a different angle. In damp conditions the soil surface presented to the combi-drill will not make for an easy job. Some time may be required for the soil to dry, during which more rain can arrive.

In the West, especially when potato harvest is rather late and conditions are wet, the easiest way to prepare for wheat is to plough, bringing up drier soil, and to drill on the same day. This is a more weatherproof system, but it plants the volunteers perfectly to preserve them and cause maximum problems in succeeding years.

Tuesday, 18 July 2017

Improving the eating quality of Potatoes

Use of nitrogen and the effect on dry matter

By Knowledge Exchange Manager, Anne Stone 

At the first field walk of SPot SW on July 4th, sixteen visitors looked at the Electra crop in Joe-S field, together with Ollie Blackburn, farm manager of Dillington Estates, Ben Mitchell and Merren Lewenden of Branston Ltd and Marc Allison of NIAB CUF.  
The topic for the demonstration arose from the experience of growers of Electra for Branston last year. As Ben Mitchell explained, 18 growers on 350ha achieved 60t/ha on average. The crop ranged from 15-22% in dry matter, and at the lower end of this range, the eating quality was poor.  Data collected by Merren Lewenden in the graph below showed how dry matter development over the season was affected by the rate of nitrogen fertiliser.

It appeared that excessive nitrogen resulted in too low dry matter percentage. Not enough nitrogen can also be damaging, as in one case on a sandy, gravelly soil where70kg/ha N was applied. The resultant tubers had 22% DM and dehydrated in store. About 19% DM is ideal and, with that target, Branston Ltd recommended 100kg/ha N for the 2017 season.

% dry matter / no. days after planting & harvest / nitrogen rates

The rebels at Dillington

In spite of that recommendation, Ollie Blackburn revealed that the Dillington Electra has received 120kg/ha this year. Nobody commented, but I’m sure we all like it when  people don’t give the ‘right’ answer.

Not so simple.

Relationship of N with dry matter is affected by moisture in the soil and varies from year to year. As Marc Allison said, in NIAB CUF research on 25 crops around the country with differing nitrogen rates, reduction of 30kg N only increased dry matter by 0.3%.  Knowing that a tidy correlation can’t be relied on each year led Dillington Estates and NIAB CUF to look at both irrigations and fertiliser as in the plan shown below. A base rate of 90 kg/ha N was applied to the whole field, with top dressing sprayed to achieve 120kg and 150kg/ha. Irrigation was scheduled for July 6th, and one side of the field will always receive less than the other.


There was a small snag setting up the demonstration. Practical problems led to spraying the top dressing later than on the rest of the farm, on June 24th.  Due to risk of scorch, Ollie chose an Omex product at 18% N, rather than the 26% N product originally planned. Still there was some scorch, especially where 60kg/ha had been applied, as the photo (right) shows.

Cheapskate Marc

In response to the question of whether sulphate of potash would help raise dry matters Marc replied that in NIAF CUF experiments there had been little difference between the results of using the sulphate or the muriate form of potash. There is a big difference in price between the two forms, making potash about twice as expensive if applied as sulphate.

 It is sometimes thought that keeping the crop green until burndown, with more fertiliser than required for yield, can protect against black dot. Marc Allison asked if those present had found that N fertiliser rates which led to yellowing of leaves from early August was associated with black dot or any other disease. No one had that experience, which encouraged Marc in his view that the low N strategy was sound.

Matt Hallett and Ben Mitchell
Whether to apply foliar nutrition was another query put to our visiting scientist. Marc thinks that although petiole tests for N are commonly used in America there is a lack of understanding of how the results relate to any benefit of nitrogen subsequently applied. He suggested that although growers are seduced by the low cost of adding foliar feed to a blight spray, these small costs add up. Similarly with trace elements, there is rarely an economic response. So his advice if you feel you really have to use a foliar feed is to leave an unsprayed strip to convince yourself over time that it doesn’t work.

With every question, Marc favoured the cheaper option. If he applies the same approach to family holidays the Allisons must have a nice time paddling at Felixstowe and Clacton on Sea.


Much of the discussion was about the end of crop life and whether there would be an effect on dry matter content of tubers if diquat is lost. A range of approaches were suggested by different visitors:

·         Flail first, one day, diquat (Reglone)at 1l/ha, followed by carfentrazone-ethyl (Spotlight) at 1l/ha

·         If lush crop: diquat at 0.5l/ha, 7 days, diquat at 1.0l/ha, 5 days, flail

·         If a senescing crop: Flail, 2 days, diquat at 2l/ha, 7 days, carfentrazone-ethyl (Spotlight) 1l/ha

·         cyazofamid (Ranman) and diquat together

·         If blight or blackleg; diquat before flailing

Delayed skin set can be a problem in Electra and two of those present mentioned times when it had taken 7-8 weeks after burn down. This is another reason for not using too much nitrogen.

When can we get an idea of the results?