During a meeting for Belgian greenkeepers, Ruud de Deugd gave a presentation on a subject which, in his view, is far more fundamental than many golf courses realise: sand and air. Not on the surface, but deep within the root zone. ‘Sustainable quality starts underground,’ he explains. ‘Yet we still too often focus solely on what we can see: speed, density, uniformity. But true stability is determined right down there.’
TopChanger performs sand injections using water pressure
In an interview with trade magazine Greenkeeper, De Deugd explains why the traditional maintenance model is reaching its limits, and why he believes sand injection using water pressure is set to become the new standard in modern green management. He gets straight to the point: if you want sustainable playing quality, you have to work underground. 'The top layer gets a lot of attention, and rightly so. Topdressing, hollow tines, solid tines, linear aeration. These techniques are essential. They incorporate organic matter, keep the top few centimetres open and improve the surface structure.' But, he emphasises, many of these methods focus primarily on what happens on the surface. 'We add sand to the top layer, but much less to the deeper root zone. Yet it is precisely there that oxygen availability and bearing capacity determine how strong and stress-resistant grass can be.'
Although established techniques remain valuable, De Deugd observes that greenkeepers are increasingly coming up against the same limitations. ‘Maintenance often follows a cycle. Compaction and organic build-up increase, problems become apparent, and then drastic intervention follows. The problem is solved for a while, but then it builds up again.’ According to him, the cause is not a lack of craftsmanship. “It’s in the system. Many interventions cause disruption to the surface. That leads to pressure from members, fewer opportunities to play and less recovery time. As a result, maintenance is postponed until problems become acute. You’re always working reactively.”
Ruud de Deugd
Air
Furthermore, in many cases, interventions only create open pores temporarily. ‘Hollow tines do not always fill the pores completely. Solid tines create space but do not introduce any load-bearing material. The furrows made by linear machines often close up again. You create air, but no lasting structure.’ According to De Deugd, it is essential that greenkeepers pay more attention to macroporosity: the quantity of large air-filled pores in the soil. ‘Under playing pressure and due to organic build-up, that macroporosity decreases. Then soil density increases and air becomes the limiting factor.’ And it is precisely air that is crucial for healthy roots. 'Oxygen moves ten thousand times slower through water than through air. If a soil profile becomes saturated quickly and drains poorly, insufficient oxygen reaches the roots. Plants always react in the same way: shallower rooting, higher sensitivity to stress, and less resilience to drought and heat.' He sums it up in a single sentence: 'What you see above is determined by what lies below.'
Sand injection using water pressure
De Deugd regards sand injection using water pressure as a logical next step in maintenance. ‘Instead of creating temporary air channels, this technique allows you to inject sand deep into the road structure. Water is injected under controlled pressure. It finds its way through the existing pore structure. The sand that comes along with it is deposited at that depth. When the pressure is released, the soil closes up again, but now around sand instead of air.’ The result? No collapsing air channels, but a stable sand structure that supports the macroporosity in the long term. Machines such as the TopChanger combine aeration with water-borne sand injection. ‘This allows you to actively integrate sand where you need it with minimal surface disturbance,’ says De Deugd.
According to De Deugd, the main benefits lie in three factors. Firstly, sand penetrates deeper into the turf profile. This stabilises the structure in areas where roots struggle to access oxygen and water. Secondly, disruption to the surface is kept to a minimum. ‘You can do it more often, as it causes golfers hardly any inconvenience.’ Finally, preventive maintenance becomes a realistic option. 'You no longer have to wait until things go wrong.' Greenkeepers working with cool-season grasses, such as Agrostis stolonifera, Poa annua and Festuca species, can, according to him, expect greater root penetration. 'And that is where the real benefit lies. An extra two to five centimetres of effective root depth can make the difference between stress and stability during hot or dry periods.' It brings about a shift in mindset: from reactive maintenance to structural root zone improvement.
Evolution
Although De Deugd emphasises that traditional aeration and topdressing remain indispensable, he sees sand injection using water pressure as a logical next step. ‘It is not a replacement. It is the evolution of the profession. Just as precision fertilisation and data-driven irrigation are now the norm.’ According to him, this changes the key question. “We no longer need to debate whether we should aerate. The question is how we can stabilise the root zone sustainably with minimal disruption.” He expects this way of working to become standard within a few years. 'Then we’ll look back and wonder why we ever did it any other way.'
Article by Wijnand Meijboom (Greenkeeper NWST)
