It was once one of the most neglected pieces of machinery on the farm. Now growers recognise that it pays to look after their fertiliser spreaders through regular maintenance, to regularly performance test them and to invest in technology that helps make optimum use of costly nutrients.

Two years ago, Derbyshire grower James Chamberlain decided the cost of variable-rate application technology had fallen enough to make it viable. He’s glad he did, because having estimated it would take four years to recoup the investment, he reckons to have broken even already.

Employing precision farming specialist SOYL to provide a soil-sampling, analysis and variable-rate mapping service pays off in terms of getting quantities right, he says. Buying a pair of Amazone ZA-M ProfiS Hydro spreaders with appropriate control technology enables him to put the rate recommendations into practice.

Operator David Archer checks the vane angle settings on his Amazone spreader…

…before setting up variable rate application using on the iPAQ computer, which communicates an electronic “map” to the Amatron+ control terminal.

“I now realise the soil analysis and spreading techniques I used before were not accurate enough,” says Mr Chamberlain. “As a result of more efficient fertiliser use and improved yields I’m recouping the investment faster than expected.”

Although he previously applied different rates within areas of a field known to have a different soil type to the rest, he was surprised to find big variations in soil nutrient status within the same field.

SOYL’s sampling routine is GPS-guided, so that repeat samples can be taken from the same location to monitor how soil nutrient status develops over time. The SoilSense service, using satellite imagery to create crop canopy maps at certain growth stages, gives a clue to areas needing more or less nitrogen to even things up.

Once decisions on rates have been made, SOYL supplies the electronic files needed for a FarmWorks-programmed Hewlett Packard iPAQ computer in the tractor cab to communicate with the spreader’s Amatron+ control terminal. In combination with a dGPS location system, the outfit can then automatically dispense fertiliser according to the electronic variable-rate maps.

“It’s paramount that you have an operator prepared to embrace this technology,” says Mr Chamberlain. “We’re fortunate that David Archer is not only enthusiastic, but also very competent.”

The ZA-M ProfiS Hydro has built-in weigh cells and a dynamic monitoring programme that compares the actual weight of material in the hopper with the weight that should be there at any given time for chosen application rate and area covered.

Any discrepancy, which may result from a change in flow characteristics due to atmospheric conditions changing through the day or different batches of the same type of fertiliser, are compensated by adjusting the hopper outlet slides.

“The Soft Ballistic System is also proving its worth,” says Mr Chamberlain. “Mineral fertilisers prone to shattering are less likely to be damaged thanks to the agitator design, the slow disc speed and gentle acceleration of product along the vanes.”

He also likes the fact that the low spreading trajectory makes spreading less vulnerable to wind distortion than with machines that cast it in a higher arc.

Being able to spread wide with accuracy was also high on the list of priorities for Martin Smart, arable manager at the West Ashton farm of P & J Awdry & Son in Wiltshire.

“We recently increased our farming acreage and one of the measures we took to make sure we had sufficient machinery was to increase tramline width from 24m to 36m,” he says. “That was good for spraying, but set a few challenges when it came to spreading fertiliser.”

Double vanes made of hard-coated stainless steel, together with a hopper flow rate of over 400kg/min, enable the Kuhn Axera to distribute good quality fertilisers with a consistent spread pattern across 36m.

With little enthusiasm for liquids, granular spreading was considered the only option and one that was resolved when tray testing confirmed that a Kuhn Axera spreader was up to the job.

“We had some concerns about spreading granular fertiliser accurately at 36m width, but the test carried out by Spreader Calibration Services set our minds at rest,” says Mr Smart. “After a series of tests with different fertilisers at different rates, the results showed it had performed accurately – more so than I’d have thought possible.”

Using a quality fertiliser with even conformation and that is resistant to breaking up is a key factor, he maintains.

GrowHow’s Heartland Sulphur 24-8-8, which accounts for the lion’s share of the 600t of compound spread each year, Nitram straight N and DoubleTop N plus sulphur compound fit the bill, says Mr Smart, with the company’s N-Min and N-Calc soil nitrogen status and availability assessments contributing to decisions on application rates.

Variable rate spreading may be the next step, but for now the focus is on making sure that blanket applications go on as accurately as possible.

The Electronic Mass Control (EMC) feature on the Axera 1102-H spreader helps in that respect by electronically regulating the flow of material to the discs and checking for any blockages.

What’s different about the EMC system is that rather than using built-in weigh cells, it works by detecting changes in oil pressure within the hydraulic drive system to the discs.

The spreader’s Quantron P terminal checks the spreader’s forward speed and the speed of each disc, and also the oil pressure either side of the hydraulic drive motor. Any variance from calculated quantity of fertiliser applied and the target rate triggers adjustment of the hopper outlet to put things back on track.

“It all works so simply,” Mr Smart enthuses. “Once you’ve entered the application rate and the spreading width, it’s just a matter of driving down the tramlines – there’s no need to calibrate.”

His final comment is a word of warning: While his new spreader has proven it can work accurately at 36m, no broadcaster can sustain its performance when the wind gets up. “You have to look at it in the same way as spraying – if it’s too windy to spray, then it’s also too windy to be spreading fertiliser,” he insists.

Spreader links

Fertiliser spreader information, including settings charts are available to growers from the following manufacturers’ websites:

• Amazone amazone.co.uk
• KRM (Bogballe/Bredal) krm-ltd.co.uk
• Kuhn kuhn.co.uk
• Kverneland (Accord) kverneland.com/uk
• Mallinson (Transpread) mallinsonfabrications.co.uk
• Multidrive (New Leader) multidrivetractors.co.uk
• Rustons Eng (Sulky) reco.co.uk
• Teagle teagle.co.uk
• Vicon vicon.eu
• Weaving (Tulip Centerliner) weavingmachinery.net