When potatoes are harvested, they respire producing heat and moisture and this is particularly noticeable when harvesting in warm conditions that we have had so far this year.

Left to its own devices, the crop will sweat and warm in the store creating ideal conditions for the spread of diseases such as soft rot, dry rot, silver scurf and black dot. The transition between field and store is a critical phase in the crop year.

The advice is simple: Set skins, dry, cool and cure – in that order. Easy to say, rather more difficult to achieve.

Good skin set is critical to a good quality crop. Much has been said and written about haulm destruction and skin set. The newer chemical treatments are simply not as quick and effective as older products.

But for newer varieties, often with thin bright skins, full skin set is even more critical to successful harvest and storage. Be patient and look critically at samples coming off the harvester. If in doubt, then move onto another crop.

Drying the crop coming into store is the next priority. Store facilities and methodology has advanced a lot in recent years with many seed growers now using ‘positive’ drying facilities. These are systems (‘letter boxes’, ‘suction walls’ and others) that move air directly through the boxes containing the harvested crop.

Using this large movement of air right through the potatoes from immediately the first box is harvested has greatly improved crop quality coming out of store. This is especially apparent for seed potato growers.

These systems can pay large dividends in a wet and difficult harvest. But, even in better conditions where the crop is coming in warm and initially dry, the reduction in condensation will improve quality coming out of store considerably.

For ware growers, a positive system can also be a benefit, but lots of air directly through the crop could result in too much moisture loss and needs to be handled carefully.

The use of ‘over the top’ fridge systems, with air recirculating efficiently around the store, is the usual system and can very effectively dry the crop over time. Air curtains and other smaller modifications to air movements can speed drying and make for a more efficient store.

After drying, the next priority is to cool the crop. Higher temperatures, especially if combined with moisture, will accelerate most disease problems.

With modern equipment and good conditions, many growers will be harvesting several hundred tonnes per day and stores will fill quickly. It's relatively easy to control the temperature in these stores once the doors have been shut and temperatures can be reduced gradually.

For stores taking longer to fill, it can be more difficult to get temperature control right. Keep a close eye on the temperature of the crop coming into store and aim to have the store temperature set just a few degrees centigrade lower. That way the incoming crop will not form excessive condensation, drying can continue and store can be gradually cooled.

Plan the pull down in temperature taking into account your crop, the market (seed or ware) and period in store. The pull down, needs to be a gradual process so that the entire block comes down uniformly. Any differences in crop temperature in the store during this phase will result in condensation and increase disease risk.

Finally, however careful harvest was, you will have damaged the crop to some extent. Curing will allow the wounded tubers to heal and prevent infection.

If skins were set and your harvester operator was doing a good job, this becomes your third priority after drying and cooling. By slowing down the temperature pull down you can give time for curing to occur. Keeping the crop dry throughout is essential.

Finally, set up a store monitoring regime that starts on day one of the critical dry/cool/cure period and continues until the last tattie leaves the store. Every year we see problems that if only they had been spotted a few days earlier could have been prevented.

Successful storage:

  • Set skins – Dry – Cool – Cure
  • Plan a store layout
  • Pick out rots, stones and mother tubers on the harvester/grader
  • Do not overfill boxes (impedes airflow, damages the crop)
  • Identify problems (blight, wet areas etc) early.
  • Take temperature of incoming crop
  • Take samples throughout harvest (skin set, bruising, quality assessment)
  • Monitor daily for condensation and store temperature