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.

Volunteers
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.

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