One Hampshire-based grower has invested in a high-tech K Two spreader with weigh cells and IsoBus control, to make the most of nutrient values with digestate from an on-farm AD plant. Geoff Ashcroft reports.
For Edward du Val of Apsley Farms, extracting maximum nutrient value from digestate is as important as the energy that forage crops generate for the farm’s AD plant.
Based at the 400-hectare Faulkners Down House, near Andover, Hampshire, the du Val family has recently diversified and installed a 6.5MW AD plant, which consumes about 110,000 tonnes of feedstock each year for power generation.
Feed comes from about 1,800 hectares of maize, 1,800 hectares of rye and 15,000 tonnes of sugar beet to be produced and harvested each year, on-contract with growers within a 30-mile radius of Faulkners Down House.
As part of the AD process, about 55,000 tonnes of solid and a further 55,000 tonnes of liquid digestate are re-applied to land being farmed. Apsley Farms’ digestate affords a typical nutrient value of about 5kg/ha.
“Both solids and liquids from our AD plant have a really useful nutrient value,” explains Mr du Val. “We now buy much less bagged fertiliser, but can still increase yield and improve the organic matter on the chalky soils we farm.
“We do not include any waste material in feedstock, and the Soil Association has awarded our digestate with organic-status. The organic matter it delivers is proving as valuable a soil conditioner as it is a slow-release fertiliser.”
While liquid is precisely applied using a Veenhuis tanker and dribble bar with NIR control for real-time nutrient analysis, getting a similarly high-tech result from solid digestate has been much harder to achieve.
“Historical data has revealed that we have been under-applying for the last few years, by about 30 per cent,” he explains.
“While we have seen improvements from contractor-based spreading services, we took the decision to invest in our own specialist spreading equipment.
“This high-tech approach will contribute to higher yields and improve traceability,” he adds.
The answer he has been looking for was found in K Two’s Bio 1820 manure spreader. This 18-tonne, twin-axle machine incorporates on-board weighing and auto-rate control, and with the introduction of IsoBus control, affords a direct link to his existing John Deere Greenstar-based precision farming system.
“We wanted a simple machine that could plug and play with any of our IsoBus-ready tractors,” explains Mr du Val. “This would make the most of precision farming technology and create spreading maps of where we have been, and show how much has been applied.”
The K Two spreader was chosen following the farm’s successful investment in six, K Two ejector trailers, to run with its JD9900 and New Holland FR920 foragers. Mr du Val says the swap from tipping trailers to ejectors has boosted logistics by 50 per cent, and positive unloading drives efficiency when unloading into a bagging machine to ensile feedstock at multiple on-farm locations.
“We now need only six ejector trailers to keep up with two 950hp foragers instead of nine tipping trailers,” he adds. “And this application of high-efficiency logistics will also migrate into our spreading activities.”
Since taking delivery of the spreader in early 2019, the farm has been keen to refine the spreading process, as farm manager Charlie Richards explains.
“We started on 24m tramlines, and we have also looked into applying some digestate on top of crops at their very early growth stages. But, this autumn we have moved up to a 36m tramline system, and this has prompted a rethink with how we use the K Twos. Where the dribble bar can achieve the wider tramline spacing, the K Two will not spread to 36m.”
With application accuracy in mind, Mr Richards and Mr du Val elected to operate on a 12m controlled traffic system for solid digestate, introducing a 50 per cent overlap to the spread pattern.
“This makes the spread pattern much less susceptible to windy conditions, and with application rates of up to 40 tonnes/hectare, it lets us travel at good forward speeds,” Mr Richards explains.
The spreader’s payload sees up to 20 tonnes carried, and with weight shared over four large diameter tyres, this creates a generous footprint.
“We were led towards 710/50 R26.5 tyres instead of smaller 22.5s, just like those on the ejector trailers,” says Mr du Val. “These travel very well indeed, and with passive steering on the rear axle, headland turns are also kind on the surface.”
Depending on tractor availability, the Bio 1820 could be used on a JD8400R, JD6250R or a JCB Fastrac 8330.
“The JCB is favoured for its comfort, but we do move the JD4640 universal terminal between cabs, to make the most of compatibility,” says Mr du Val.
“Applications are made to stubbles or cover crops in spring, ahead of cultivations and drilling; and again in the summer, ahead of autumn cultivations and drilling.”
The required application rate is keyed into the tractor’s universal terminal and the spreader handles the rest, using auto-RTK steering guidance for application accuracy. Though IsoBus is not used to manage tractor transmissions.
“There is no need to go that far, given that one load will cover half a hectare,” he says. “With the pto speed set, the spreader’s weigh cells will adjust the moving floor to match ground speed and maintain the desired application rate.”
Mr du Val says the spring and autumn spreading windows allow the farm to apply its logistical processes to hauling solid digestate. But rather than use its ejector trailers, the farm operates a fleet of six articulated lorries with walking-floor bulk trailers. The same haulage team is also employed to bring maize and rye back to Apsley Farms on-demand, to keep the AD plant working at full capacity.
“Running trucks lets us move a lot of digestate out to farms, in preparation for spreading,” says Mr du Val.
The spreader is loaded with a JCB 435S loading shovel equipped with a 5cu.m bucket, with six passes filling the spreader.
“We have tried running the spreader as a one-man system, and also as a two-man team, to see what generates the most efficiency when using just one spreader,” he says.
“A two-man team costs more to operate, and there is increased waiting time and fuel efficiency losses when the loader is sat idling waiting for the spreader to return.
“But we may yet end up with a second K Two spreader,” he says. “Output would double and the loading shovel would not have much opportunity to sit idling. And that would give us the ability to easily apply over 1,500t/day.”