Bringing slurry equipment into the realms of sprayer technology, Oxfordshire contractor RC Baker is boosting application accuracy of slurries and digestate with the help of dribble bars equipped with section control. Geoff Ashcroft reports.
While slurry application would appear to lack the precision of fertiliser spreading, it is by no means a poor relation.
Advances in application technology have put liquid waste management at the top of the agenda for many. And Oxfordshire contractor RC Baker, based at Spring Hill Farm, Barford St Michael near Banbury, is no exception.
Each year, the firm applies about 200,000 tonnes of liquid waste for customers, with the lion’s share of material in the form of digestate – the liquid waste from AD plants.
Equipment for the task includes two Claas Xerion-based spreading rigs – one using a Kaweco tanker, the other an SGT/Saddle Trac combination.
“Investment in specialist spreading equipment provides our customers with many benefits,” explains RC Baker’s operations manager Stephen Baker. “We can put liquid exactly where it is needed, and we know exactly how much has been applied, which meets NVZ rules.”
“And because the system is virtually odourless, we can apply right up to field boundaries against residential areas without complaint.”
“We can put liquid exactly where it is needed, and we know exactly how much has been applied,” says Stephen Baker.
Mr Baker says the appetite of the two spreading rigs affords a high degree of efficiency too.
“We can move and apply large volumes of liquid very efficiently – and with full traceability – using these two machines,” he says. “And more and more customers are viewing liquid waste applications as a valuable nutrient source, rather than simply applying a byproduct somewhere, just to get rid of it.”
With application increasingly taking place on tramlines, the firm relies on several boom options for its two tankers.
The 24 cubic metre capacity Kaweco can be equipped with a 15m trailing shoe Bomec boom – which can also operate at 12m. But it can also be used with a 30m Vogelsang dribble boom, which can operate at 24m and 27m widths.
Wider application is possible using the 32m boom fitted to the firm’s SGT/Saddle Trac outfit, and this too can be operated at 24m and 30m.
Added precision comes from the Vogelsang booms which use Exacut macerator/distributors. These hydraulically driven units cut and distribute material to the dribble bar outlets.
With Comfort Flow Control (CFC), application management is taken a step further, which uses rubber balloons inside the outlet pipes. Operated by compressed air, the balloons are inflated to block the outlets. Releasing air pressure allows material to be pushed past the collapsed balloon.
Air-operated CFC valves manage liquid flow for section control, tramline switching and management of hose groups on the dribble bar system.
And it is the integration of CFC which has enabled section control, tramline switching and management of hose groups on the dribble bar system.
“CFC gives us a little more operational flexibility,” says Mr Baker. “It means we don’t apply liquid into the tramlines; we can close off sections to meet different tramline widths and we can manage overlaps.”
“But the system is not automatically controlled – it’s all done manually from the cab.”
Like many levels of sophistication, Mr Baker’s challenge comes from making advanced levels of technology pay its way.
“Our customers are happy with the sophistication and professionalism we deliver – if we were to move to an automated section control system, who would pay for the extra investment,” he asks. “There is not enough research done on establishing the true value of digestate, so at this stage, there is no tangible extra benefit for our customers by opting for such an advanced application control system.”
“There are too many variables in the entire application process,” he adds.
There are greater benefits to be had, he believes, from improving logistics.
Coupling directly to D-Tec artic tankers means the entire load can be transferred in about four minutes.
Currently, the firm relies on haulage companies to bring digestate to blocks of land ready for application.
While a portable nurse tank affords a degree of in-field bunkering capacity, the majority of liquid is off-loaded directly from the road trucks to the spreaders.
“The SGT rig can couple directly to D-Tec artic tankers and remove the entire load in about four minutes,” says Mr Baker. “And if we can manage the flow of liquid from store to field, we can easily apply 1,000 cu.m/day.”
When it comes to weight distribution, the SGT/Saddle Trac combination boasts an even split over its three axles, which are shod with 900/60 R38 and R42 tyres. A positively steered tanker axle ensures precise following in-field, and boosts manoeuvrability.
“It is fantastic on tramlines,” he says. “We can get liquid placed on the ground among the crop, at a rate of six cubic metres/minute.”
Liquid management between the outfit’s two 16 cubic metre tanks ensures the Xerion’s chassis-mounted tank is the first to be filled and the last to be emptied. As a result, traction is always assured.
“Traction and manoeuvrability are fantastic, but it doesn’t ride quite as well as the Kaweco – the fourth axle and goose-neck mounting make a huge difference to ride comfort and overall boom stability on the smaller tanker,” he says.
That said, he points out that the Kaweco unit is no less sophisticated.
Xerion Saddle Trac/SGT combination uses a 32m boom for accurate distribution of liquid waste.
A hydraulically controlled suction arm is fitted to the smaller Kaweco tanker, and using twin 150mm (six inch) pipes, can fill the 24cu.m capacity (24 tonne) tanker in about two and a half minutes.
“We might add two more metres to the boom, so we can increase our versatility,” he says.
With lagoons thoroughly stirred 24 hours ahead of spreading, liquid consistency and nutrient value are uniformly distributed throughout the volume. Regular sampling determines exact content of N, P and K, with application rates tweaked according to nutrient value to achieve the required target rate.
“Applications are driven largely by crop growth stages and timing,” he says. “Digestate is very much viewed as a fertiliser application, so it needs to be applied at the right growth stage, and in the correct quantity for it to be of useful value to a growing crop.”
While that quantity varies according to crop needs, he says typical rates vary from 15-35cu.m/ha. And the average nutrient value of digestate offers the equivalent of 4kg of N per cubic metre.
“We can often make three applications into standing crops, right up to flag-leaf stage,” he says. “Importantly, using a dribble bar system makes liquid slurry immediately available to the growing crop.”
“Compared to splash-plate spreading systems, this really is in a league of its own,” he says. “We place liquid on the ground, right where the crop needs it; crops are no longer coated with manure, and because we’re not spraying liquid through the air, we’re not losing nitrogen to the atmosphere and creating unpleasant odours.”