It is wet years such as this one that really bring home the importance of good storage facilities, and particularly those with positive ventilation. John Sarup of Spud Agronomy offers his four top tips for managing potatoes going into stores this autumn.
1. Measure tuber temperature at harvest
Why bother? First to ascertain how long wound healing will take and thus how much curing should be allowed. Next it helps 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 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 by 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 into 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 that can be loaded quickly (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 (higher than 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.