Near Bourne in Lincolnshire, arable farmer Daniel King believes that the auto shut-off system that is fitted to his new 24m Chafer Guardian trailed sprayer has saved him at least £3500 in product cost, effectively paying for itself in its first year.

In March this year Mr King replaced his eight-year-old 3000-litre Chafer 24m E-series with a new 4000-litre Guardian and has already sprayed more than 1700 hectares (4200 acres) with it.

"Increasing tank size was a major reason for changing the sprayer," says Mr King. "We needed greater output in order to apply liquid fertiliser on wheat at a rate of 288 litres/ha in two splits giving a total of 225kg/ha of nitrogen," he says.

"I am able to cover 14ha per fill up so I am getting much more work done."

"A key point though is that we can also achieve higher output on the agchem side. This means we are able to select the right time to spray rather than have to go at any opportunity even if it's not ideal timing."

The sprayer is fitted with a TeeJet rate control system, which automatically maintains the preset application rate regardless of forward speed. There is also an LH AgroCentreline GPS guidance unit up in the cab, which lets the operator know the direction to head in.

Having these two systems on-board means it is possible to link them together to provide automatic boom section switching.

In effect, the GPS unit indicates when the sprayer's boom sections are approaching an area of the field which has already been sprayed and switches off that bank of nozzles.

Individual boom sections on the Chafer Guardian switch on automatically as they reach unsprayed areas of the field, prompted by LH Agro's Swath Manager GPS system.

Similarly, as the operator enters a new run from his headland turn, the required boom sections spring to life.

Mr King says it is difficult to quantify the product benefit and savings from moving to a bigger sprayer with auto shut-off. But he knows that he still had 6t more liquid fertiliser in the tank at the end of this season compared with 2006, having covered the same area of land.

With fertiliser costing between £230 and £270/t, this represents a saving of £1380-1620 a year.

"With large booms there is obviously the potential for more overlap so having an automatic shut off system is a major advantage because the same part of the crop is not treated twice," he says.

"Clearly with the price of fertiliser being so high it saves us a lot of money and there is also a reduced chance of over- or under-dosing on the agchem application side."

Estimated savings on agrochemicals amount to £2000 over 1450 acres across both his and a neighbour's land, with an extra £1000 saved on the 500 acres being contract farmed.

Daniel King reckons to have saved well over £3000 this year having switched to a 4000-litre sprayer with automatic boom section switching.

Much of the savings have been made on the headlands.

"The system has paid for itself already," he says. "We usually have a problem with our wheat lodging somewhere on the farm, especially at angled field margins.

"Rather than overlapping by up to 3m in places, we are now down to just 25cm."

Having auto shut-off means he can now concentrate on driving and turning on headlands, rather than watching where he is spraying. It also means he does not get so tired or lose concentration.

When applying liquid fertiliser Mr King says he is able to travel at 16-20kph (10-12mph) and at 12-17kph (8-11mph)when spraying pesticides .

"Auto shut off is easy to operate and it helps to improve driver performance and accuracy. I have tried to confuse the system to see if there are any flaws, but I can't.

"However, it can be overridden to manual. It's a bit like a mobile phone - you wonder how you ever managed without it."

AUTO BOOM SHUT-OFF

• Avoids overlaps/misses, so saves on wasted sprays/fertiliser
• Reduces lodging risk at headlands
• Speeds up/eases headland turns, so higher output
• Reduces operator workload, so lower fatigue, can use less experienced drivers

GPS SPRAYER CONTROL SYSTEMS COMPARED

Supplier	GPS unit	Auto section shut-off	Contact
LH Agro	Centreline (£1995)	Swath Manager (£2000)	01480 496 367 or  www.lh-agro.co.uk
Precise Solutions	Trimble EZ Guide Plus (£1350)	EZ boom (£1350)	07850 471 216 or www.precise-solutions.co.uk
Patchwork	Raven Enviso (£2000)	Accuboom (£895)	01291 6733 66 or www.patchwork.co.uk
John Deere*	Starfire SF1 receiver (£1497)	Sprayer Pro (£1435)	Local dealer or www.deere.com

*Only available for new i-series sprayers