7 March 1997

Be cool is BS message when crop is in storage

Most beet has now left the clamp and been delivered for processing. But was it delivered in best quality? Robert Harris examines British Sugars latest work to protect crop quality

HEAT, rather than cold, is the main enemy of stored beet, so good ventilation should be the main consideration when designing a clamp, says British Sugars operations manager, Ian Hopkinson.

Usually, growers wont notice anything is wrong, he adds. "The centre of the store can rise to 30C before you see visible signs, such as steam." But hidden losses mount up – at 20C (68F) sugar losses are twice those at 10C (50F).

The aim is to keep clamp temperature close to outside air temperature, says Mr Hopkinson. Ventilation is the key. In BS trials this year clamps averaged 5C (41F), the same as a fridge.

BSs trial clamp at Hibaldstow aerodrome, Redbourne, Lincs, sits on a concrete pad. Designed to reflect grower practice, it contains 350t of beet – 2.5m high, 10m wide and 22m long. Walls are big square bales stacked two high. "One bale is ideal, with shoulders of the beet clamp sloped to ensure adequate ventilation," Mr Hopkinson advises. But lack of space means most growers insist on two bales. Such clamps hold about 10% more beet. "That is fine in a cold year like this, but in a warmer year clamps wont vent so well."

Bales on pallets

Bales stand on pallets to aid ventilation. Air is drawn through these up through the clamp. Beet should be clean for air to move freely and free from bruising.

Even the best clamp filled with clean, undamaged beet needs good sheet management, he maintains. Once ground frosts reach -2C (28.4F), the clamp should be covered. When temperatures rise, the sheet should be removed again. "Too often growers leave sheets in place w hich stops ventilation."

In a cold year, losses may be minimal. Last year in a BS storage trial to compare a managed clamp with a permanent sheeted one, the permanent sheeted clamp showed sugars fell 0.11% a day, only slightly more than the managed store. But in the warm winter of 1993/94, temperatures in the centre of the permanently sheeted clamp rapidly rose above ambient (left graph). "The store was out of control. Temperatures eventually reached 28C, and sugar losses reached 0.25% a day."

This years managed trial clamp shows the ideal, with store temperature closely following the ambient (right graph), says Mr Hopkinson. As a result, he expects similar results to the 22 trials carried out over the past five years. Average losses of total sugar in beet stored for 35-85 days were just 0.1% a day.

Monitoring the temperature of clamps managed in different ways is helping pinpoint best practice, say BSs Ian Hopkinson (right) and Charles Fletcher. Findings should be implemented by next season.


KEEP IT COOL


&#8226 Keep store temp as low as possible, but above -2C.

&#8226 Allow recently harvested beet to cool before sheeting.

&#8226 Place bales on pallets to aid ventilation.

&#8226 Handle beet gently.

&#8226 Keep soil, trash and green material to minimum.

&#8226 Maximum store dimensions – 10m wide, 2.5m high.