Spud special: Wet season piles pressure on storage

It is difficult to sit down and write my report without filling it with doom and gloom, poor yields, poor weather conditions, poor harvesting conditions, growth cracks, hollow heart, internal rust spot, pink rot, tuber blight, blackleg, waterlogging…the list goes on.


Yes, the free market price is good, but the majority of crops are grown on contract and a lot of growers are not even covering the cost of production. Certain parts of the country are worse than others and a recent trip to Lancashire brought this home with a number of potato fields underwater.


It is years like this that really bring home the importance of good storage facilities and particularly those with positive ventilation, however over the last few years there has been little margin for reinvestment. It is about time that the whole industry realises that if climate change continues and weather patterns result in more extreme weather events, investment needs to be made for continued potato production to remain sustainable. 

Anyway, for this year we have got what we have got and we must get on and deal with it and, hopefully, the following points will help in some way.

1.         Measure tuber temperature at harvest

 Why bother? First, to ascertain how fast wound healing will take and thus how much curing should be allowed.  Secondly, to determine whether there is a large temperature differential between crop already in store and that being placed in store which might result in condensation.  Ideally the store temperature should track the temperature of tubers coming in from the field.


Finally, to help evaluate risk of bruising. Generally dry matter % is quite high this year, however, as yet I have seen little bruising to worry about, probably due to soil moisture at burn off.


2.         Ventilate into store

 Removing field moisture and heat from respiration of the tubers and thereby avoiding condensation is crucial in the first few days of storage.  This means effective air circulation.


This can be achieved reasonably using outside air such as in Dutch Barns (natural ventilation) or by pulling outside air in (using fans and louvers), but without care condensation is possible and humidity control is difficult unless there is an air mixing system between in-store and outside air.


Positive ventilation overcomes many concerns about condensation and is particularly important for crops in a year such as this with soil and rots going in to store.  When using outside air, use air that is within 4C of the tuber temperature, cooler is usually better.  Using a fridge unit to dry and ventilate can achieve good results but is better suited to stores which can be loaded quickly (e.g. within a week). The first few days in store generally determine how well storage diseases are controlled – where a risk of disease occurs.


3.         Temperature pull-down

 No matter whether the crop is for seed, pre-packing or processing, for long term storage, temperature pull-down should begin as soon as the crop is cured and be finished within a few weeks.  Where tubers are coming into store warm (over 12C) by using the fridge to ventilate and dry, the process of cooling can start as soon as the fridge is full.


4.         Store Monitoring

Monitor the store closely, particularly for temperature fluctuations and condensation which might indicate breakdown.


One thing is for sure next year will probably be completely different to this year and there will be more challenges to face us, both as growers and advisors and as such it is vitally important to get the fundamentals right, focusing on field and variety selection, cultivations and seed quality all backed up by sound R&D based advice.

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