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Planning the 2017 crop

29 September 2016

Matching the right variety to the right field is the first and most important step to growing a profitable potato crop. Grower Gateway examines the key factors to take into account

Harvest may still be in full swing but thoughts are already turning to next year’s cropping plans. Deciding which fields will be planted with potatoes is only half the story, says Phil Burgess, head of knowledge exchange at AHDB Potatoes.

“To optimise performance, we want to know as much as we can about the fields we intend to crop and as much as we can about the varieties we want to grow, to come up with the best match. Getting it right can make a big difference to the bottom line.

“People will be selecting fields and making rotational decisions, and there are a lot of different considerations to take into account. In addition, there some good new varieties that quite a number of growers will be trying commercially for the first time.”

The first step is to check the end market. The key drivers then are the land on which the variety will be grown, and how its agronomic profile fits with the location and enterprise, he advises.

“Spending time now to check soils could pay dividends. Most importantly, dig some holes, look at what’s there and use your experience to plan how to use the soil to its best advantage.

“Is there compaction? Does the soil type vary across the field? Are there any drainage issues? How many stones? Should you be planting the whole field?”

‘Think soils’ is a useful guide to help in soil assessment, he adds. “This can be downloaded from http://potatoes.ahdb.org.uk/agronomy/soils along with other useful information on soil management.”

Key agronomic factors

Once soils have been checked, fields should be ranked according to likely lifting dates and whether the crop is likely to be stored, and for how long, says Rob Blades of SPUD Agronomy & Consultancy.

This will help narrow down the choice of suitable varieties according to crop maturity and resistance to key storage diseases such as tuber blight, dry rot, blackleg/soft rots, he advises.

“Growers taking on new rented land should also find out when the field last grew potatoes and possibly the number of potato crops – this provides the best guide to soil-borne diseases such as rhizoctonia, pink rot or black dot,” he notes.

The topography of the land is also important, says Mr Blades. “Misty, sheltered corners can be a haven for blight, for example.

“When assessing land, also take note of the weeds, particularly those that are over-wintered stubbles. They can act as a reservoir for diseases – tobacco rattle virus, which can cause spraing in certain varieties, is a good example.”

Variety choice is further fine-tuned by testing for PCN, in known problem areas. “If you have no experience of the land, take particular care when sampling to optimise the chances of picking up patches and smaller hotspots.”

It is important to understand whether varieties are resistant or tolerant to PCN, he adds. “Resistant varieties prevent nematodes from multiplying on roots, but if they are not tolerant nematodes can still affect root systems and you can end up with a very poor crop.”

If PCN is present, growers and landowners can also consider the long term implications of variety choice on the long-term sustainability of the rotation. The PCN calculator, also available on the AHDB website (http://potatoes.ahdb.org.uk/online-toolbox/pcn-calculator) is a useful tool to assess the implications of rotation length and variety choice on the PCN population.

Determining water availability and that permissions are in place to use it is important not only for yield, but also quality, says Mr Blades. In conjunction with the water-holding capacity of a soil, water availability can be a key factor influencing variety choice, particularly for pre-pack growers concerned about the effects of common scab on skin finish.

AHDB work is producing good evidence that less water can be used on more resistant varieties than many growers realise. Traditionally, on medium soils growers apply 12-15mm of water once the soil moisture deficit reach 15mm, but this is based on the needs of a susceptible variety like Piper.

Varieties with intermediate resistance to common scab can tolerate an SMD of 20mm or more, the equivalent of an extra two days without irrigation, and resistant varieties upwards of 26mm on medium soils, which buys a further couple of days (see http://potatoes.ahdb.org.uk/sites/default/files/Seasonal%20Water%20Manag...)

Nutrient testing

A soil test for key nutrients should then be carried out. “As a minimum you’d want to test for macronutrients and pH,” says Mr Blades. “Those who don’t know the soil should get a full micronutrient assessment as well.”

Growers can then assess key requirements including nitrogen for the varieties they are growing by using the AHDB online calculator (http://potatoes.ahdb.org.uk/online-toolbox/fertiliser-calculator).

As a final check, growers who are considering growing a new variety and/or taking on new land should talk to other growers and/or local agronomists and breeders, Mr Blades suggests.

“It’s all about knowing your varieties, and playing to their strengths. Some are better suited to certain soils and areas. There is little hard evidence to show this, but it is well worth finding out about other people’s experiences through local first-hand knowledge.”

AHDB variety selection tools

AHDB has several tools to help growers fine tune their selection, says Dr Burgess. The main tool is the AHDB potato variety database (http://varieties.ahdb.org.uk).

“This provides data on potato varieties that have undergone resistance testing for key pests, diseases and pathogens within the AHDB Potatoes-funded Independent Variety Trials (IVT) programme,” he explains.

The database allows growers to:

Search for varieties by name or characteristic
View variety data individually or by two-variety comparisons
View independent assessments of agronomic characteristics (such as bruising susceptibility) and resistance to a wide range of diseases.
Obtain grower, breeder and breeders’ agent contact details to source seed and varieties.
See lists of varieties, images, variety breeders, seed marketing agents and related industry organisations.

A further tool provides a list of this season’s movers and shakers that provides an indication of new varieties with growing demand that are worth a try on farm, says Dr Burgess (http://potatoes.ahdb.org.uk/publications/update-potato-plantings-variety...).

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