Late potato planting – patience now can result in better yields

Friday, 13 March 2020

It has been one of the wettest winters on record, with many parts of the country suffering damaging floods. In wet areas planting may be many weeks away yet.   Patience and risk mitigation now, can help prevent poor results come harvest – says AHDB’s Graham Bannister.​

The key message is not to panic, waiting a few days and planting in the right conditions is often better than ‘losing’ a couple of days growing time.

This article describes some of the key risks associated with the timing of planting, and highlights some resources available to help manage them. We would always recommend talking with your agronomist or advisor before acting, or you can find your local AHDB Knowledge Exchange Manager here.

Avoid compaction

Planting in wet conditions can lead to yield losses larger than that you would experience from delayed planting.

Mark Stalham of NIAB CUF said:

Serious yield loss due to late planting only really starts occurring after 7 May in England for a Group 3 determinacy variety. With longer daylight hours in Scotland, this may even be a few days later. The risks are associated with delayed emergence and the crop not reaching full cover by the longest day of the year.

On the other hand, poor soil conditions can lead to compaction, Mark said that it is “highly likely that a 2 – 5t/ha yield loss may occur if poor soil conditions lead to compaction.”

There is more information on the risks associated with compaction and how to reduce them on pages 12 and 13 of: Soil management for potatoes. Compaction often occurs when the soil surface is dry but it is wet below the surface. Simply digging a hole to inspect soil plasticity sits in the field you are intending to plant, should do the job “…you should not be able to form a string of soil 3mm thick” said Mark Stalham.

Seed spacing

Mark Stalham of NIAB CUF said: “The shorter season and potential compaction issues means that tuber size is likely to be smaller owing to lower yield. Seed spacing needs to be widened to achieve the optimum size specification”.

AHDB has seed rate guides for eight popular varieties here. The guide works on a planting date of the 15 April, so this will give you a starting point from which to begin. There have also been demonstrations conducted on seed spacing at SPot Scotland results can be viewed here

Nitrogen requirement

A shorter season will reduce the nitrogen requirement for the crop. The Nutrient Management Guide (RB209), Section 5 (Potatoes), contains tables (page 22) with suggested nitrogen rates based on growing season length.

Mark Stalham said:

A shorter season will typically reduce the N requirement (by 20, 13 and 10kg/week for Group 1, 2 and 3 determinacy varieties, respectively).

The tables also take into account the amount of winter rainfall and your varieties determinacy group, providing a good guide for your nitrogen rates.

Planning for burn-off

Getting nitrogen rates correct this season will take on extra importance, due to the loss of popular desiccant diquat. Spotlight and/or Gozai straights or combinations, along with flailing, can give nearly as quick desiccation as diquat – but it is likely to be an easier job if the crop is approaching natural senescence. Over doing it on your N rates mean you could be faced with a lush green canopy to tackle, while using an unfamiliar strategy.

In the winter we considered what else to consider before you plant, in order to make burn-off go as smoothly as possible.

Health and Safety

At this time of year, you and your team are likely to be putting in long hours to get the job done. It is important to ensure you are working in a safe way, our Safe Potato Operations video series is here to help.

Further reading

GREATsoils Soil Management for Potatoes Seed Rate Guides Nutrient Management Guide RB209 Safe Potato Operations Excess winter rainfall monitoring

Graham Bannister

Senior Knowledge Exchange Manager - Potatoes
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