LOADING a potato store should be an activity that is planned well in advance of harvest and it is important to match crops, in terms of their quality, likely storage periods and market expectations, to the storage available, so management is effective and returns are maximised.
Crops should be lifted as free as possible from damage, soil, stones and haulm. Within an hour or two of entering store, the crop should be ventilated to remove surface moisture from tubers and from any remaining soil.
If positive ventilation is available, as in bulk stores or lateral suction (Aspire) or letterbox pallet stores, ventilation will prevent condensation forming on tubers in crops lifted in dry conditions. The airflow removes warm air produced by the rapidly respiring crop and will reduce the likelihood of the warm air condensing on the cooler potatoes above. Try to load stores within a week and absolute maximum of 14 days, especially if there is going to be a lot of field heat to remove. This ensures potatoes can be brought under optimal control and reduces the need to compromise on store management and, ultimately, crop quality.
Field sampling will identify rots, blemish disease, tuber defects or cutworm/slug damage, while warm storage (>20°C) of samples before harvest can identify potential rotting prior to loading. Crops with rots, or loads which have been rained on, should be kept out of the main store to prevent contamination. Crops with 1–2% rots should be set aside, ideally in boxes, and positively ventilated continuously for 4–6 weeks until any rots are mummified.
During store loading, the temperature of the crop already in store should, ideally, track the daytime average temperature of the crop in the ground, usually between 20°C down to 10°C, over the harvesting period.
The store should be ventilated whenever the outside air is within ±4°C of the crop temperature to ensure all surface moisture is removed and condensation is not caused. If dew-point temperature sensing is available, it can be used instead of temperature to prevent condensation when ventilating with air warmer than the crop. Crops should be quickly blown dry to prevent disease development, which will be encouraged by the relatively warm temperatures during this period, if crops are respiring heavily.
Damage prevention at harvest will be a challenge this year after such a lengthy dry period. Of course, mechanical damage when loading should be kept to an absolute minimum. Rots and blemish diseases invade through wounds and broken skin, while bruising risk is highest in dry years and is a primary cause of rejection from premium markets.
Testing for damage should be routine so increased damage can be quickly identified. Standard methods of damage assessment are available; use 25-tuber samples and categorise damage into slight and severe and measure the proportions ideally by weight but tuber number will also work (less accurately).
Hot-boxing samples overnight will help to show any bruising. Take 25-tuber samples from known locations to identify any sources of bruising. Again, classify tubers by peeling and identifying slight (one or two peels) or severe (more than two peels) bruising percentage.
Get into a routine of repeated sampling so that you can monitor any changes resulting from a change of field, variety or machine operator. All of these factors have a potentially huge bearing on the crop going into store and it’s too late to find out you’ve bruised the crop when it comes to trying to deliver a crop after storage.
Use an automated swinging-head elevator for systematic loading of bulk stores as it avoids the formation of soil ‘cones’. Also, while most automatic box fillers are designed to minimise drops into boxes, pay attention to detail with conveyors and screens as these are often a source of bruising during loading.
STORE managers need to be getting geared up for the new season just round the corner, according to Adrian.
Adrain recommends using the following as a checklist of kit that will be needed:
Adrian has spent more than 35 years working in applied research, knowledge transfer and best practice advice on all aspects of potato storage. Having headed up the Sutton Bridge Crop Storage Research facility from 1989 until its closure in 2021, he now runs his own consultancy and collaborates on industry initiatives and training days.
