Good ventilation of crops in store wards off disease
Good ventilation of crops in store wards off disease
Potatoes are highly perishable, so attention to detail at every
stage of the storage process is essential to avoid losses.
Andrew Swallow relays advice from Sutton Bridge Experimental
Units Adrian Cunnington on how to get it right
Load potato stores quickly and start ventilating from an early stage, says Adrian Cunnington (top right) of BPCs Sutton Bridge Experimental Unit.
RAPID drying of potatoes as soon as they go into store will be the key to maintaining crop quality throughout the storage period this season, according to the British Potato Councils Sutton Bridge Experimental Unit.
"Get the ventilation on as soon as you possibly can," says operations manager Adrian Cunnington. "It has such a bearing on the quality of the crop in store, especially on blemish diseases such as silver scurf or black dot."
That makes drying the crop especially important for growers intending to sell to pre-pack markets, but processing growers should also aim to dry the crop without delay to contain any rots, he adds.
"Use the ventilation system as soon as you have enough crop in store for it to function effectively. Thats once two or three ducts are covered in a bulk store, or once there are 50-100t in a box store."
Ideally, the best quality crops for storage should be lifted first, leaving the worst to last, assuming that the first in will be the last out.
In wet conditions, considerable soil is likely to be carried off the field and as much as possible should be removed on the grading line. Extra care is needed to prevent soil cones forming in boxes or bulk stores, which could limit ventilation. "Keep the elevator head moving," says Mr Cunnington.
Stores should be loaded quickly, but do not risk damage to the crop. Try to fill one store at a time and close it up within a week to 10 days.
"If it takes longer than that, look at splitting the store up in future years," he suggests.
It is essential to stack boxes correctly so airflow is not impeded. "If you do need to leave an aisle, then it is important not to allow any shortcuts for the ventilation. Block off the aisle with polythene or plywood," says Mr Cunnington.
In bulk and box stores, a level surface is important to prevent condensation pockets. Straw covering is essential if bulk stores are uninsulated.
A curing period is more important for later lifted crops, when damage levels are higher and disease pressure increases. Ten days at 10C should be sufficient for pre-pack varieties, but processing crops may require up to 14 days at 14C.
At the end of the curing period, temperatures can be pulled down as fast as possible for pre-pack crops, but more care is needed for processing markets.
"Processing potatoes dont want any kind of thermal shock. Limit cooling to 0.3-0.5C a day."
The target holding temperature will depend on outlet and variety. Russet Burbank may be stored as low as 6.5C without affecting frying quality, but a variety such as Lady Rosetta must be stored at 9-10C. Growers should check what is required with their processor, agronomist or Sutton Bridge, he says.
Most pre-pack potatoes can be stored safely at under 4C, which means sprout suppressant can be limited to one application. If CIPC fog is used, it should not be applied until four to six weeks after the curing period because it inhibits wound healing.
The warmer holding temperatures required for processing may mean more CIPC applications are necessary. Where CIPC fog is used, make sure seed is not stored close by. *
SPUD STORE LOADING
• Fill fast but avoid damage.
• Ventilate from start.
• Prevent soil cones forming.
• Loading and curing: monitor daily.
• At holding temperature, inspect twice weekly.
Monitoring tips
During loading, curing and the pull-down period, Adrian Cunnington recommends stores are checked daily. "They need to be inspected closely so you will spot any condensation," he says. Temperature probes should be placed as the store is filled, mostly at the top of the store with about one probe for every 100t of potatoes. A few placed lower down the store will help identify any temperature gradients, he says. Once the holding temperature is reached, a routine of twice weekly inspections should be established, with at least one inspection being a thorough check of the whole store.