Farmers Weekly Interactive

Spud Special: Pause in potato planting prompts rethink

If you are a potato grower in Scotland then you may now start to wonder what you have done wrong in the world. The only comfort is that it’s not just Scottish growers. Planting is varied with many seed growers still to start while some ware producers have over 60% in the ground.

Crops planted in March into dry warm soils appear to have gone through their lag phase prior to the cold, wet April. These crops have or are emerging under fleece and in open crops. Those crops planted just before the heavy rains have moved little and their destiny hangs in the balance with an increased risk of poor emergence, rhizoctonia and free living nematode feeding damage.

When planting does restart growers need to think about strategy. There could be a benefit in increasing spacing in ware crops by 10-15% in all but very low tuber number varieties.

Unlike last season size is likely to be at a premium and wider spacing will provide crops with more chance in getting to size without extending the harvest window and jeopardising quality. There is no advantage to reducing planned nitrogen other than in indeterminate varieties or processing crops where sugar stability is required.

Early senescence makes the crop more prone to black dot, bruising and also drought stress, whereas the effect of nitrogen delaying tuber initiation and bulking have been over emphasised and are unlikely to have a major impact on yield.

Early low Erwina bacterial counts of many seed stocks are unlikely to still represent a low risk of blackleg. Seed sitting in cold, water-logged ridges or, even worse, sitting in bags in a poorly ventilated ambient shed in England is unfortunately going to mean that bacteria are going to multiply rapidly with a further risk at planting if de-sprouting occurs.

Store seed in boxes not bags and ventilate to prevent condensation to minimise risks.     

Matthew Smallwood

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