27 August 1999

Seed quality vital for


Three potato growers won

through to on-farm judging in

the farmers weekly/Fungazil

100SL Potato Grower

Challenge. Charles Abel

profiles the second finalist,

from north Norfolk

MANAGING 830ha (2050 acres) of potatoes across a range of soil types on five farms in north Norfolk is no mean feat. Add the strict quality criteria of a major crisper, and Simon Alexander has his work cut out.

Based at Trimingham, near Cromer, he manages crops as far away as Fakenham and Great Yarmouth on soils ranging from reasonable clay to sandy loam. Over 35,000 miles are covered each year in his quest to keep a close eye on crop development.

With just 660mm (26in) rainfall a year, the area is classed as semi-arid. "Keeping unirrigated crops going is one of our biggest challenges," says Mr Alexander.

To produce the correctly sized tubers desired by Walkers and achieve target dry matters, plant spacing is managed very carefully. Most seed is ordered from known suppliers on a provisional count, checked after dressing and re-checked on arrival in Norfolk.

Planting rates are based on ind-ustry guides, site and a lot of experience. "Spacing is widened a shade where we know it helps," he says.

Skin finish is not critical, so the main seed disease concerns are blackleg and rhizoctonia stem canker. Samples of 50-100 tubers a batch are washed and inspected and Monceren (pencycuron) used where rhizoctonia is a concern, especially on Hermes. All seed is treated with Fungazil (imazalil) or thiabendazole.

Variety choice is designed to meet storage requirements, with Atlantic suiting direct supply from the field, Lady Rosetta and Hermes going from the field or early/mid-term storage, Pepo longer-term storage and Saturna full-season storage.

Each variety has its own management needs, especially when it comes to plant spacing and dry matter, says Mr Alexander.

Rosetta is also blackleg prone, so seed source is an important consideration, Saturna can be fickle on tuber numbers and Hermes is distinctly shy, he says.

Planting starts in mid-March and aims to finish in six weeks. Seed is not chitted. "Theres no point unless you have the right handling equipment. If you havent, you lose 98% of chits and merely increase blackleg loading." Instead 1t boxes are held cool and seed planted with eyes open.

As harvest approaches, regular test digs monitor crop quality, especially dry matter. "We do our own hot box bruising tests and use an electronic potato to assess damage."

The crop is graded into 1t boxes or bulk and stored mainly on member farms, with Mr Alexander ensuring temperature is carefully controlled to avoid frying problems.

The net result is a rejection percentage in the low single figures. "With crops washed before despatch we dont want to be sending produce that is going to be returned," Mr Alexander says. &#42


&#8226 North Norfolk Potato Growers manager.

&#8226 830ha (2050 acres) potatoes.

&#8226 90% Walkers crispers.

&#8226 5% seed, 5% chipping.

&#8226 BASIS qualified.

&#8226 Quality control key.

&#8226 Enviro concern.

&#8226 Yield: 45t/ha.

&#8226 Variable costs: 3/ha (3/acre)

&#8226 Seed 717 (290)

&#8226 Fertiliser 235 (95)

&#8226 Herbicide 34 (14)

&#8226 Fungicide 187 (76)*

&#8226 Insecticide 335 (136)

&#8226 Desiccant 62 (25)*

&#8226 Total 1570 (635)

* Estimated.

Precision use of crop inputs

Potatoes are typically grown on a one-in-five or six rotation with wheats, barley and beet. Some land is rented in.

Nematodes are targeted with Telone (1,3-dichloropropene) plus nematicide applied on the clod and stone separator according to need. "We try to avoid Telone, only using it where populations are over 30 eggs/g and considering it at 20-25," says Mr Alexander.

"Potentially GPS nematode testing can help a lot, but results need careful interpretation and like any sampling it needs doing right. You need to know the field and its history. Weve rechecked where we were unsure and it has paid off."

Fertiliser rates are adjusted according to variety and soil analysis. Nitrogen rates are 220-260kg/ha (176-208 units/acre), split two-thirds in the seed-bed and one-third on top.

Rain-gun irrigation is scheduled according to a balance sheet and although scab control is not needed, Mr Alexander is keen to start earlier. "You can tell when the crop is ready."

Blight fungicides are bought competitively from a range of suppliers.

If aphids appear, aphicide is used early, Hallmark (lambda-cyhalothrin) going on before bees, ladybirds or lacewings move into the crop. If later protection is needed Aphox (pirimicarb) is preferred, apart from inseed crops where a move to Decisquick (deltamethrin + heptenophos) is warranted. "But we rotate actives to avoid resistance pressure."

Crop stimulants are not used, but a foliar feed cocktail goes on if roots start failing due to nematodes or drought. Magnesium as bitter salts is also used.

Environmental considerations include the use of alternate products for LERAP buffers. "For larger fields the headland gets an alternative, for smaller fields the whole fields gets it." The herbicide Arresin (monolinuron) replaces Linuron (linuron) near ditches and in blight sprays Curzate (cymoxanil + mancozeb) goes on instead of Invader (dimethomorph + mancozeb), for example.

Narrower set-aside strips instead of buffer zones would be a boon.

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