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Have you used the variety seed rate guide?

1 August 2011

Growers who used the new AHDB Potatoes variety seed rate guides this season are being asked to feed back their findings to help fine-tune further publications.

Five guides designed to boost marketable yield whilst optimising seed rates in Maris Piper, Maris Peer, Saturna, Hermes and Lady Rosetta were published in time for planting in spring 2010.

Together with the previously published Estima guide, the new series, based on AHDB Potatoes research at Cambridge University Farm, now covers 43% of the British ware area, says AHDB Potatoes seed specialist, Drummond Todd.

The new series of guides differs from previous recommendations in that it accounts for the effect of seed age, as well as size, on optimum seed rate.

“The effect of seed size on stem number and, in turn, optimal spacing is well known, but CUF research has shown that seed age can also have a significant effect,” says Drummond.

Older seed, like larger seed, tends to produce more stems and can result in smaller tubers. Likewise younger seed will produce fewer stems and may need a higher planting rate, he explains. These findings have been distilled into the new recommendations.

“We asked growers who used the guides to plant a few drills at the rates recommended in the guides and compare the results with their standard practice,” he explains.

As well as hearing how crops turned out, Drummond would also like feedback on how useful growers found the guides, to help format the new ones, which include Marfona and King Edward, as effectively as possible.

Grower comments should include how helpful, accurate and user-friendly they found the new guides, in addition to any problems encountered. For example, growers must know the actual chronological age of the seed to ensure the recommendations are correct, says Drummond.

“Ideally, this is the period from the emergence of the seed crop to the planting of the ware crop. If no information on seed emergence date is available, then the date of the first herbicide can be used.

“Seed suppliers should be able to provide this information, though sometimes seed can pass through several hands before it arrives on farm.”

storage conditions can alter the effect of chronological age, so seed arriving several weeks before planting and kept under less-than-ideal conditions might not produce the same results as another batch from the same crop delivered immediately before planting, he adds.

“Delayed planting will also advance the effective seed age and affect the resultant stem numbers, so adjustments should be made,” says Drummond.
“We need to be ‘belt and braces’ about any new approach,” he adds. “If your normal seed rate differs greatly from the guides, why not try a half-way house spacing and compare with usual practice? For instance, some growers prefer to plant using narrower spacing in heavier soils.

“The key thing is to remember your customers' specifications and to use the guides to help you meet specific target average tuber sizes at a given yield.”

Growers should email results and comments to

Information should include;

• Variety
• Date of 50% emergence of seed used
• When delivered and source (grower or merchant)?
• Storage conditions if not ‘just in time’ for planting
• Target yield and average tuber size
• 50kg tuber count of seed
• Derived spacing
• Planting date
• Soil type or any other factor that normally influences seed rates
• How the recommended seed rate compared with standard practice
• Marketable yield under each regime