Spud Special: No Ryder Cup style comeback for spuds

There has been no Ryder Cup style come back for the potato crop this season. Most crops went into the end of the season three weeks behind and that is generally where they have finished in yield and size fraction. Despite some late September sun those growers who risked growing crops on have seen little bulking in the last three weeks and now face the lottery of a November harvest in Scotland.

Drainage has been the key factor in crop success with waterlogged soil preventing bulking for long periods compounding the lack of sunshine, resulting in growth cracking in many crops and greening through tubers setting just under the surface of the ridge.

There has been a north south divide with crops north of Aberdeen having a relatively normal season in terms of rainfall and therefore crops are better. South of Aberdeen all crops have suffered with Borders and again Fife worst affected.     

The season has not been without its surprises, with dry matters against most growers’ expectations at 2-4% higher than normal. This is probably a result of the dominating factors of early senescence and low nitrogen availability to the crop during the season driving early dry matter partitioning. This was unable to be matched by reduced capacity for the plant to take up water usually associated with tuber bulking.

Although not widely reported yet, the early senescence and higher starch levels associated with higher dry matter could lead to tubers becoming hyper sensitive to bruising. Sensitivity can change within hours, so growers need to check bruising levels before harvesting the field by performing drop tests.

In contrast to last season, there is a potential risk of rotting in store from progressive blackleg as well as soft rots associated with water-logging and there are some reports of tuber blight. In the case of blackleg there are some cases where the rot is going into heal end at harvest and this is impossible to spot on inspection tables and will end up in store.

In these cases prolonged positive ventilation is going to be needed to dry up the tubers breaking down and prevent the development of rot pockets. This is also going to be a requirement for soft rots and any pink rot present. Unlike previous seasons there could be more of a relationship between foliar infection and tuber blight. Growers can assess risk by keeping tubers at room temperature and looking for symptom development after two weeks.

The one thing that is no surprise this season is the amount of powdery scab. Unfortunately a wet tuber initiation period in all regions of Scotland has resulted in wide spread infection. In high pressure situations, no matter what has been applied to seed crops, it has not been enough to make a difference.

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