The benefits of deep aeration

Dave Saltmanin Consultancy

The benefits of deep aeration

Chat forum with David Green, Managing Director, Terrain Aeration

Editor: Welcome to another chat forum, where we are pleased to have David Green the Managing Director of Terrain Aeration joining us. Good evening David.

David Green: Good evening to you and all your members.

Editor: Feel free to ask David questions, but to kick off can you tell us a little bit of your history, please David?

David Green: I've been in and around the aeration business for the last twelve years, using pneumatic fracturing machinery to improve localised drainage and reduce surface waterlogging on cultured turf. We originally used machines imported from Germany but unfortunately their reliability was so poor, we had to redevelop the machinery before offering a contracting service.

Editor: So you've developed the machinery yourself?

David Green: Three or four people developed the machinery in different ways during the early years, but I've stuck with the original German injection method and concentrated improvements on the carrier vehicle, the rams and hammers now seen on the machine. All of these improvements have been built into the machine with the intention of speeding up the machine, making it easier to use and to radically improve reliability.

Editor: The machine that you have out working today took you how long to develop?

David Green: We have a series of machines out at the moment, though I think you're referring to 'Airforce', this machine has taken two years and is only now at the position where I have just ordered the final protective bonnet and guards.

David Green: We have a further machine that has taken two years to develop. This is designed to be used in confined spaces and accesses such as domestic rear gardens.

Editor: When will this machine be available?

David Green: The machine will be available this autumn with a launch at Saltex.

Editor: Perhaps we ought to discuss the principles of these machines to the members?

David Green: Pneumatic fracturing is the base principle of all the machines that have come to be known by the generic name of terralift. They come in different sizes but all work on injecting gas at high pressure into the subsoil where the almost explosive release of gas causes the soil to lift and in our case to fracture.

Editor: At what sort of depth do your machines work?

David Green: Our optimum depth is at one metre where the spread of effect reaches an average of one and a half metre radius from the probe.

David Green: We can go deeper, and have in the past been down to depths approaching three metres but this is highly specialised and there is not much cause to go this deep.

Editor: So simply how does the machine mechanically work?

David Green: All the power comes from a petrol or diesel engine driving compressors and hydraulic pumps. The air is compressed up to about 20 bar or 300psi and the hydraulic components work to 2000psi. There is a vertically mounted mast not unlike a forklift mast, which carries the hammers, probes and injection system. The hammer and the ram force a 37mm diameter hollow probe into the ground and the air is released from slots at the tip of the probe.

Editor: How long is the probe?

David Green: The length of the probe is defined by the working depth, so I use a one-metre probe to go in a metre!

Editor: You mention gas then air, what's the difference?

David Green: One of our competitors uses nitrogen gas, which is commercially available, relatively cheaply, and bone dry. The advantage of this is that you don't need heavy compressors and engines, just a pipe connection to the gas bottle. The disadvantage is that nitrogen gas displaces oxygen in the soil and then causes the roots to suffocate. By using air, we're injecting just the medium that the roots require, the downside is that air is very wet and you do need heavy equipment to compress it. Roots however require the oxygen content that we inject.

Editor: I know that you have other materials available to inject into the ground can you elaborate on these for us please?

David Green: The principle product that we inject is dry milled seaweed, which has some interesting properties. The material when dry is light and friable and so can be mixed with the air before injection, once in the ground the material sticks to the sides of the cracks and fissures that have been made and absorbs soil moisture. This causes an expansion of up to ten fold by volume.

Editor: Why is that important?

David Green: Because it holds the cracks and fissures open, creating easy access for air and water to percolate through the soil. The seaweed can be used as a carrier for Mycorrhizal fungal spores, oil digesting bacteria, water storing polymers and of course any fine grain fertiliser or soil conditioner required.

Editor: Ok Where do you see this type of operation providing the biggest benefit to the ground?

David Green: Hard stressed sports turf and by that I mean football and rugby, winter sports pitches. Trees, particularly new plantings. Golf and bowling greens where we're one of the few aeration systems, and certainly the only deep aeration system that doesn't disturb the playing surface.

Editor: How much area can you cover in a day?

David Green: Simple question, complex answer; The area depends upon which machine we are using and soil conditions on site. For 'Airforce' our large machine 2000 square metres per day is a reasonable average. For the small back garden machines, about 600square metres would be an average.

Editor: Just going back, what Mycorrhizal and oil-digesting bugs do you use and how effective are they?

David Green: We buy in these products from trade suppliers; there are different types for different applications.

Editor: How do you know which to use?

David Green: There are two answers to this, bugs first, we need a core sample from the area, to determine the nature of the pollutant and to establish how long the pollutant has been there and how deep it's travelled. The different bug mixtures will vary with type of pollutant and time it's been there. The second one is the Mycorrhizal fungi, where type of tree and soil type are the determining factors, also the age of the trees concerned.

Editor: Moving on, how long does it take to do a football pitch?

David Green: The average pitch is about 6000 square metres, and so to treat it would take three days or so, but in our experience the full treatment is hardly ever required and we tend to do the middle third of the pitch, eighteen yard box to eighteen yard box.

Editor: Just going back, you never mentioned the effectiveness of these bugs and fungi, it must be the heavy excesses of the bank holiday weekend that have clouded my mind!

David Green: The bugs have a clean up rate, given favourable weather conditions, acceptable to all the major insurance companies. From their point of view it is an effective remedial treatment. Like all biological remedies, the temperature of the environment is paramount, so summer applications work far quicker. The same is true of the fungi, and results are generally noticeable the following season. Trees usually have improved canopy, bud formation, leaf density and better fruiting.

Editor: How long does the deep aeration treatment last?

David Green: Between 3 and 5 years for areas with heavy use such as football fields. One treatment lasts a lifetime for areas that have low traffic such as ornamental borders.

Editor: What are the clear benefits of the treatment of deep aeration?

David Green: The treatment produces an environment favourable to root growth. The deeper the root system the more volume of soil that can be exploited by the plant and so a greater amount of soil water and nutrients are available. And as I stated earlier, drainage from the surface to the subsoil is speeded up so that surface water drains swiftly after rain.

Editor: You mentioned treating fine turf- how do you convince the Groundsman/Greenkeeper that there will be no disturbance?

David Green: Occasionally with great difficulty, in which case we can either put him in touch with any of our previous customers or arrange a demonstration on a less critical area to put his mind at ease. We do however carry a first aid kit that contains a defibrillator to bring them back around :)

Editor: What do you do with the probe holes that you create and how many of them are there?

David Green: First of all, the probe holes are every four square metres, that is two metres apart from each other. We stagger each run, so the first may start at 1,3, 5, 7, 9 metres and the second run at 2, 4, 6, 8 metres and so on. We have a choice with the probe holes, we can leave them open, backfill with inert aggregate that will not damage mowers (Lytag), fit a drainage tube (particularly around trees) or we can part fill with aggregate, topped off with a preferred top dressing.

Editor: Is compaction a real problem and what evidence do you regularly see of this?

David Green: Compaction is certainly a big problem because people are now using sports turf far more frequently and in adverse weather conditions. The use of heavier machinery, and the advent of concerts and outdoor events where winter sports pitches are used to take the traffic all combine to crush the air out of the soil. We detect compaction while using the machine by a change in the amount of effort needed to force the probe into the ground. We generally find an area between 250mm and 500mm below the surface, where the probe finds the most resistance.

Editor: 250mm is probably getting below the area that a more usual aeration machine like the vertidrain will deal with, this must give you an edge?

David Green: In one pass, our machines will provide full decompaction from the depth of one metre to the surface. One operation by us, will then enable more standard aeration techniques to be continued effectively.

Editor: Can you treat cricket wickets?

David Green: We can treat cricket outfields but unfortunately not wickets, our loosening of the soil profile will cause variable bounce, however we can supply a Drill 'n' Fill service for these wickets.

Editor: What would you say were the main selling points of your aeration service to prospective clients?

David Green: Up to date we have tended to be trouble-shooters, called in to sort out a problem after many other avenues have been tried. We are called in because the last option available to many is a complete new drainage system. However we have also been called in when a new drainage system has failed to do the job, where you get green lining. Green lining is where the grass has grown well where water has drained away over the top of the drain, but not from the areas between the drains. We would then operate between these lines to break up the soil between the drain lines. I suppose our unique selling points are minimum surface damage combined with deep based, long lasting, effective surface drainage and aeration. Because the aeration is long lasting (years), it is therefore very cost effective. As far as possible the entire operation is eco friendly; we even use green hydraulic oils and fuels.

Editor: Some people might be worried about tree root damage from the blast of air?

David Green: At the point of the probe there is some minor damage caused to the immediate rootlets, however the benefit of all the fissures and cracks created to a depth of a metre, allows for quick recovery, fast expansion and improvement of the plant or trees root system.

Editor: After treatment how long do you need to wait before the treated surface is playable?

David Green: The answer is immediately, we've worked on waterlogged areas, with problems of a compaction pan, and the area has been fit for use immediately after our operation. Some of our great successes have been on traditional clay cup greens, where irrigation has been installed and the Greenkeeper needs to break through the puddled clay to improve drainage.

Editor: The immediacy of the operation must be a benefit?

David Green: We've had occasions where games/race meetings were in jeopardy, when our treatment has so improved the ground conditions, that despite further heavy rain, play has still been possible.

Editor: In the past my experiences have shown that a solid tined pitch, even down to 250mm has not always been enough to save a game, instances where all the holes have filled with water, and not drained anywhere?

David Green: I agree with you, I've seen this all to often, but the extra depth of the probe and the fractures and fissures made by the air blast, all combine to take the water away from the surface because of the increased capacity in the subsoil.

Editor: David, I would like to thank you for your time this evening, it's been very interesting.

David Green: It's been a pleasure, thank you and good night.

Closing notes about Terrain Aeration

The company are the only operators of the unique original terralift injection system in the world. After the theft of several terralift machines in 1994, David re-designed the firing system as there didn't appear to be any other terralift parts available. Since the launch of the company, Terrain Aeration have been able to source and purchase some terralift parts from the German manufacturer, parts he had stored in a warehouse.

The company do not envisage selling the terralift machinery as it is unique, and once an area has been treated, it doesn't need treating again for many years. It is the company aim to keep improving the technology and keep an open mind as to the different applications that can be used. All soil, turf and trees benefit from the deep de-compaction technique. For further information please contact Lynda Green on 01449 673783 or e-mail

Article Tags: