Store copes with three crops
By Andy Collings
IN the main, crop driers tend to be purpose-built to cope with the demands of a specific crop. On-floor grain driers, for example, require a drying system with different capabilities than those needed by, say onions.
On a farm growing a variety of crops having special drying and storage needs the cost of constructing individual stores can be prohibitive, as the Symingtons discovered when they took on 256ha (640 acres) of extra arable land last year.
Farming at Sutton Bridge on the Lincs/Norfolk border Ian Symington and his son Jamie were faced with a dilemma. Already running over 800ha (2000 acres), the addition of the extra acreage posed challenging problems on the crop drying and storage front.
The new farm at nearby Wingland Marsh had few if any suitable buildings and an investment in a new drier/store was clearly essential. And the problem was also compounded by the fact that a decision had been made to start onion production.
"We needed a store which could cope with all three of our main crops – wheat, onions and potatoes," explains Jamie Symington. "We planned to use it for onions in June, wheat in September and October, and then from October, use it as a controlled environment to store potatoes."
Enter Harvest Installations and, more particularly, the companys Mike Wilson.
"It was a reasonably tall order to design an economical system which could cope with these three crops," he says. "With the short periods of time allowed to dry the onion and wheat crops, the system clearly had to be efficient."
After several months consultation a plan was finally decided upon. The 1800t (onion) capacity store was built in two halves with a central plenum corridor used as the division. Four fans were positioned above the tunnel to blow air down into it – each fan has a gas heater rated at 2m BTU positioned at the air inlet.
To create the correct environment for potato storage, four chiller units were installed at strategic points around the store and the whole building was insulated.
Special attention was made to ensure that the ventilated floor was strong enough to cope with heavy traffic and, indeed, the weight of the crop.
For onion drying – a two-stage operation – the mandate was to enable 720t to be blown at 250 cu ft/min/tonne, equal to 180,000 cu ft/min at 2in swg. Heaters should be able to maintain a temperature 30C over ambient temperature.
The second stage of the drying process required the fans to ventilate 1800t at 100 cu ft/min at 2in swg.
"The timing of the stores construction means that this year will be the first time it has been used for onions," says Mr Wilson. "Fingers crossed, everything should be OK."
Wheat however, has been in the store. Due to the limited time available to dry the crop (the potatoes are only weeks away), it was decided to install two Harvest Maxi stirring units running on rails along the sides of each half.
Total capacity is 2400t stored at a depth of 3.8m (12ft) and supplied with up to 50 cu ft/min at 4in swg and heat to maintain 45C over ambient temperature.
"Most of the wheat last year went into store at about 18% moisture," says Jamie Symington. "We had a few minor problems – part of the learning curve – but we reduced moisture very rapidly down to 15%."
For the potatoes, which are held in 1t boxes – 900 on each side – the requirements were for the ventilation system to be able to reduce and maintain crop temperature at 2.5C.
This is where the chiller units, working in conjunction with the main fans, come into their own.
With stirrers, fans, heaters and chillers to look after, the control unit could have looked like Concordes flight deck, but Mr Wilson was keen to see that operation was kept in its simplest form.
"Weve installed a comprehensive system which I hope Mr Symington and his team will find user-friendly – there is little point in over complicating this part of the system," he says.
So, what are the views of the Symingtons so far? "Apart from a few teething problems I feel that the system is one that will work for us," says Jamie. "But it will be the onions that should provide the greatest test."
Help with cost
And the cost? "The whole project has cost some £400,000 – a price with which we have had some generous assistance from our landlords – the Crown Estates. Without this help I dont feel we would have seriously considered its construction," says Jamie.
But what of the need to remove and sell crops to make room for the next – are there commercial penalties for a system that does not allow the markets to be fully played?
"The onions are grown on contract, so they are spoken for at that time of the year. We have always sold some wheat early to help us with our cash flow and, once thats gone we have a clear run through the winter and spring to market the potatoes.
"Basically we have three systems in one, and should there be a price penalty to pay for selling wheat early, the money saved in not having to build three separate stores must surely compensate us for it." *