One company is C&P Soilcare, based near Ipswich, which uses Terralift machines to aerate subsoil to a depth of 1m at a pressure of 20 bar.
The other firm, Terrain Aeration — run by husband and wife David and Lynda Green of Stowmarket — split from C&P Soilcare five years ago and now manufactures its own similar machine.
The original Terralift was manufactured in Germany by a now defunct firm called Eugen Zincke Motortechnik. Previously, compacted subsoil had been broken up by detonating small dynamite charges underground, but this method was clearly unsuitable in the vicinity of underground electrical cables.
Terrain Aeration’s David Green says: “The German firm anticipated a big production run. It made lots of high-quality aluminium castings, which would cost about £300 each to replace now.”
But sales were disappointing. The units were high maintenance with low reliability, and put the user under quite a lot of stress, according to David Green, who rectified the faults before leaving C&P Soilcare.
C&P Soilcare general manager John Warren says: “No other machine can aerate to the same depth. Though the original equipment had a hammer powered by compressed air, which was not as effective, so we now use a hydraulic model, which is also safer.”
Terralift’s fate contrasts with that of manufacturers of shallower aerators. Many golf course and football pitch groundsmen include aeration as part of their annual turfcare regime, and firms such as Imants of the Netherlands, Toro and John Deere of the US, Cheshire’s Sisis, EarthQuake of Staffordshire and Charterhouse of Surrey manufacture soil aerators catering for this.
It is perhaps surprising that, although many people attest to the value of deep aeration, there are fewer machines being manufactured now than there were in the past. Earlier hand-held models from Terravent (which used pressurised nitrogen rather than air) and Robin Dagger appear to have vanished from the UK marketplace.
“Whether or not anyone else comes along and develops another machine that can do the same job remains to be seen,” says Warren.
As C&P Soilcare can no longer get parts from the defunct German manufacturer, it makes its own bespoke parts when necessary. “We can put most things right,” Warren says. “Though there is still a Terralift operation in the US we could use if it came to it.”
Curiously, the American firm sells its deep aerators not for turf or tree restoration but to improve drainage in leach fields for household waste water.
While Terrain Aeration’s process has general acceptance within the industry, Green says the company has had to cope with a number of setbacks. One machine blew up and another trailer-mounted machine was stolen from outside a Little Chef. An attempt by police to launch a search by helicopter was thwarted by fog and the machine was never recovered.
Terrain replaced this machine with one manufactured by Turin-based Pneumofore in 2003, but it broke down after a short time. It was modified at the Italian factory, but was then found to be in violation of health and safety regulations. The company was left without a functioning machine, which cost it £40,000 in lost orders.
Terrain found that the solution was to build its own models, which it has made commercially available.
The Airforce Tracker, launched at Saltex in 2004, has a JCB road drill to break through hard pan. It is mounted on twin rubber tracks and is designed for small areas, such as domestic gardens, where access may be limited. The hydraulic pressure is provided by a trailer-mounted generator, which may be situated some distance away.
The Airforce Scamper, launched a year later, is a sit-on model designed for use in larger areas such as golf courses.
Both of these machines and the Terralift models have the capacity to disperse a granulated seaweed mix into the subsoil, which, according to Green, expands on contact with moisture, helping to keep open newly created fissures, as well as delivering nutrients. Alternatively, Green adds, biological agents can be dispersed. “These can be used to absorb contaminants such as diesel in the subsoil of polluted land.”
The technique can also be applied around tree roots, often when they have become compacted by pressure from machinery during building work. In such cases a proprietary mycorrhizal tree root feed can be applied to the decompacted subsoil, rather than the seaweed mix.
Warren says: “Depending on the site, you may need to go back and do it again in four or five years. But then, it still works out cheaply when you look at the cost of putting in a full drainage system, and the fact that even that will deteriorate over time.”
The clearest symptom of subsoil compaction is poor drainage. This weakens the turf by waterlogging the rootzone, and inhibits regrowth. This could be a pre-existing problem on the site, or it could be caused by sustained pressure on the surface.
An example of the latter is at Pontypridd’s Ynysangharad Park, which played host to singer Tom Jones’ South Wales homecoming in May 2005.The park has no permanent stage, so one had to be built over the football and cricket pitches. The pressure from this, as well as from 20,000 fans, caused compaction and unevenness, which Terrain Aeration was called in to address.
Rhondda Cynon Taf Council parks officer Geraint Jenkins says: “We needed to get the cricket pitch ready for the summer season. It was part of the deal with the concert promoters that the pitch had to be returned to its former state, which it was.”
And the landscape industry’s IoG Saltex show, at Windsor Racecourse in Berkshire, itself causes compaction problems that need to be addressed before horseracing can recommence.
The racecourse general manager, David Mackinnon, says: “The turf below the tracking which crosses the course becomes very compacted. For the past two years we have aerated as soon as it is removed and have found it to be a very effective process.”
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