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East-West Split Highlights Potato Establishment Differences

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As potato planting gets underway, leading agronomy firm Hutchinsons is reporting stark differences in how growers should get crops off to the best start given the extreme variations in field conditions across the country.

Potato planting

Unusually dry weather in south-eastern areas could make early irrigation worthwhile on some crops, whereas the situation is very different further west where planting progress on wet soils is behind schedule and patience is vital to avoid compromising crop establishment.

Early Irrigation

Soils are drier than usual across much of East Anglia and the southeast following below-average rainfall during March and over the winter, which has allowed planting to progress but could hinder early development, says Hutchinsons root crop technical manager Darryl Shailes.
“Once potato crops are in the ground it is essential to get them up and meeting in the rows as quickly as possible.
“Irrigation is often used for scab management early in the season but it can be easy to underestimate the need for water early-on purely for canopy development. In dry years it can be a game-changer for crop establishment and maximising yield potential. So even where scab management is not so crucial early water can be.
“Growers in dry regions should consider irrigating as soon as the crop emerges in extreme situations, but don’t go too early as beds can be washed down.
“Don’t forget, irrigation models assume the ground is at field capacity on 1 April, but I’m pretty sure a lot of fields in the southeast won’t be anywhere near that this year.”

Darryl on irrigator
Darry Shailes

Waiting Game

In contrast further west, Herefordshire agronomist Andrew Goodinson says recent wet weather has hampered planting progress, which he estimates to be around 20% behind normal. Some chitted crisping varieties such as Lady Rosetta had been planted on light land by the start of April, and some early chipping Amora, but progress has been frustratingly slow for many.

He urges growers to be patient and wait for soils to dry-out properly, rather than forcing seedbeds in sub-optimal conditions and causing compaction that will seriously affect crop growth and yield potential. Growers must also allow enough time between bed preparation operations for soil to dry-out sufficiently, he says.

“Potatoes have a great ability to catch up and compensate for a few days delay, so it’s really not worth the risk of going too early. It’s such a big investment you can’t afford to get it wrong.”

Mr Shailes agrees. “You cannot afford to have compacted seedbeds for growing potatoes. Working the soil on the wrong day is the worst position to be in.”
As well as damaging soil structure, planting too early on wet soils also risks increasing the incidence of black leg, rots and Rhizoctonia, Mr Goodinson warns.

Andrew Goodinson HS
Andrew Goodinson

If seed is being used from different batches or sources, he suggests always growing a reference sample of each batch in the same field so that any differences in performance attributable to seed quality can be highlighted. The Hutchinsons Fenland potato trial site is examining seed quality in more detail.

Starter Fertiliser Boost
The use of starter fertilisers, either placed with seed or worked into the soil before planting, can help early crop establishment, notes Mr Shailes.

Trials show the benefit to canopy growth is most pronounced in dry, cool years, whereas in “normal” springs there may be less benefit, he says. “Many growers choose to do it as an insurance policy given the vagaries of the weather.”

Mr Shailes says the jury is still out on the advantage from applying split doses of nitrogen fertiliser and applications are best timed so that nitrogen is available for the period of peak crop demand which occurs during the rapid canopy establishment phase.

Focus on Pre-Em Herbicides
Weed competition is another threat to yield and both experts agree that efforts should focus on pre-emergence control given the limited post-em options in potatoes.

There are a number of residual herbicides to consider, even after the impending withdrawal of linuron, the last use of which must be by next June, says Mr Shailes.

Key options include products based on metobromuron, metribuzin, prosulfocarb or clomazone.

“In many respects the new metobromuron-based product is stronger than a comparable linuron-based product, when mixed with the other actives available. It also has better crop safety characteristics across a range of soil types.”

Indeed, minimising risks to crop growth is a top priority for all potato herbicides. Mr Goodinson says pre-ems should always be applied at least one week before crop emergence to avoid any detrimental effects.

While many growers will opt for a single residual herbicide application just prior to emergence, on some soil types there may be a case for using an earlier dose after planting followed by a second application, adds Mr Shailes.

For example, on heavier soils in areas prone to drying out it may be worth applying an early residual herbicide while seedbeds are still moist just after planting, before going back with a second application later. There is little value in such an approach on lighter, sandier soils, as their proneness to moving around reduces the efficacy of residual chemistry if it is applied too early, he notes.