Heat treatment keeps soil clean and costs down
Heat treatment keeps soil clean and costs down
Is sterilising soil using heat
treatment a cost effective
and chemical-free way of
killing-off weed seeds and
pathogens? Norfolk-based
UK Sterilizers believes so
with its latest UKS 2000
machine. Andy Moore reports
COLLECTING and then roasting soil at an awesome 1300C (2372F) might seem a drastic method of killing off soil-borne diseases and weed seeds.
But such a method is reality for a soil sterilisation machine – the UKS 2000 – which when compared with methyl bromide chemical treatments, is claimed to cut costs by up to £555/ha (£225/acre).
Made by Nicholson Engineering, the tractor-trailed UKS 2000 is marketed by UK Sterilizers, based at Southery, Norfolk.
Inspiration for building the UKS 2000 came from a smaller, self-propelled machine, the UKS 750, which was developed by UK Sterilizers for sterilising root crop seed beds in greenhouses.
"The main aim with the machine is to provide an organic and cost-effective alternative to using chemicals such as methyl bromide which are eventually likely to be banned," says David Nicholson of UK Sterilizers. "After successful trials with the self-propelled machine, we built the UKS 2000 for sterilising field seedbeds destined for high value root crops such as carrots, onions, sugar beet and potatoes." Trials with the self-propelled machine have been conducted over the past three years and have so far proved successful. "The self-propelled machine has effectively eradicated pathogens and weed seeds over a three year period, increasing root crop yields by up to 10%," he adds. "We believe supermarkets will advocate the machine as part of an organic farming system and may offer the vegetable grower a premium price for root crops."
Requiring 120hp plus, the UK 2000 operates on ploughed/power harrowed ground, using a 1.83m wide lift header to pick up soil. The header comprises a ground driven roller and hydraulically powered auger tiller to lift and condition soil from a depth of between 10cm and 30cm.
The header is lowered into work by two hydraulic rams operated by the tractors oil supply, with fine depth control adjusted by a crank handle.
"Working depth is typically set to 25cm, although this will vary according to previous cultivations and pathogen depth," explains Mr Nicholson. "Inevitably, deeper working and damper soil types such as peat will reduce workrates and increase operating costs."
After the lifting process, soil is thrown onto a hydraulically powered elevator, where it is then transferred into the furnace – the heart of the machine.
Similar to a lorry concrete mixer, the furnace comprises a barrel which is rotated by a hydraulic motor, powered by two 80litre/min pumps driven by a 200hp V8 Deutz diesel engine. The engine also powers hydraulic motors for the auger tiller, elevator and rear clod separation webs.
Inside the 5m long furnace, a 3m long flame produced by a diesel burner raises the temperature to 1300C, gradually heating the soil while it turns over internal helix plates.
Red diesel is pumped to the burner from four tanks positioned between the wheels to maintain an even weight distribution, while a fifth tank supplies the engine.
"Soil is heated in two ways – direct contact with hot metal inside the barrel and through hot air produced by the tumbling action of the internal plates," says Mr Nicholson. "Achieving the correct temperature depends on initial soil type and temperature, which can vary from 5C to 25C in summer."
Maximum operating costs for the machine working in peat soils are calculated at £3890/ha (£1575/acre), compared with £4446/ha (£1800/acre) for a single methyl bromide application
At the end of the furnace, soil falls on hydraulically powered webs which separate large clods from fine tilth. Large clods fall in front of the web and are then covered over with the fine tilth which forms a ridge at the back of the machine.
The outer tilth layer falls out of the machine at about 70C (158F) and gradually transfers heat to the inner clod layer, raising its temperature to 65C (149F) over an hour and a half hour period.
"A temperature of 65C is required to effectively kill off weed seeds, while 55C is sufficient to exterminate pathogens," says Mr Nicholson. "To ensure moist soil such as peat is thoroughly heated, the barrel and/or the tractor forward speed can be slowed down to ensure a slower throughput. Due to the slow forward speed, workrates vary from one to two acres a day." On the control side, the panel can be used to start the engine and monitor barrel/engine revolutions, together with temperature of the formed ridge.
Inside the tractor cab, the operator can view ridge formation through a CCTV monitor, while at the same time varying the speed of the barrel. *
The UKS 2000 from Norfolk-based UK Sterilizers is claimed to save up to £555/ha (£225/acre), compared with treatment costs incurred with a methyl bromide chemical application.
Soil is collected by a 1.83m wide Auger Tiller header which lifts and conditions the soil before being delivered onto a transfer elevator.
David Nicholson of UKSterilizers believes the UKS 2000 steriliser is a cost effective alternative to chemical treatment applications.
Operating costs
£/acre * Peat Silt Sand
Fuel 18p/lt 828 648 468
Labour £10/hr 230 180 130
Depreciation 10,000hrs 345 270 195
Repairs £7.50/hr 172 135 97
Total 1,575 1,233 890
*25cm depth over 23hr period