• Wed. May 25th, 2022

“Our grass improves even during winter”

An assessment by the official German FA pitch consultant has shown that the grass of the Veltins Arena in Gelsenkirchen has increased its root length as well as sward density during the past winter. This is a remarkable feat, given the fact that the area experiences less than 50 hours of sun per month during winter.

The Veltins Arena, home ground of FC Schalke 04, is situated in the western part of Germany. Statistics from the German weather service show that the area experiences moderate temperatures throughout the year, with cloudy and wet conditions during winter. The average humidity hovers around 80 percent, with, on average, 20 rainy days each month during winter. The number of sunny hours dips below 100 in October and only touches the required 120 in March again. It is fair to say that the circumstances provide anything, but good natural grass growing conditions.

100% natural no longer an option

The Veltins Arena is a fully enclosed multi-purpose venue that has a retractable surface. The field is moved indoors only for home games. “For many years, we would replace our surface twice a year. Apart from the finances associated with this, this also meant that we had twice a year a period with a worn-out pitch, which, shortly after the change, would be very vulnerable as the new grass still had to settle in,” explains the Veltins Arena technical director, Bernd Funke. As the pitch remains outside the venue for most of the week, it should benefit from the natural weather conditions. “Unfortunately, the local circumstances are not good enough for the grass to fully recuperate naturally from its use. At present, we use it 50 hours per year, but we had a time where it was used over 80 hours during a season. Yet we still struggled to have a good, flat and stable surface.”

Light support

To support the natural grass growth, the Veltins Arena took ownership of grass grow lighting in October last year. “Natural grass surfaces in Germany require 15 DLI. The moment that is not available naturally, it needs to be supplemented,” explains Horst Theisen, the CEO of Rhenac Sports LED, the supplier of the technology. DLI is the number of photosynthetically active photons, or individual particles of light in the 400-700 nm range, that are delivered to a specific area over a 24-hour period. “It is a very delicate exercise whereby the compensation points start at around 100 micromol. The moment you get close to the 600, you’ll be adding too much light support which will cause too much stress on the grass plant. This will result in less photosynthesis.” According to Theisen, LED technology allows delivering the required light with pinpoint accuracy, providing you know exactly what it is that the grass needs.

Improved result

When the Veltins Arena took ownership of the system, it asked independent consultant Dr Harald Nonn to assess the quality of the pitch. Nonn did the same in mid-April this year. “What really struck me was that the rootzone development had increased from 3.9 centimetres to 5.6 centimetres, despite it being winter,” the consultant explains. He also noted an increase in sward density. “This is also remarkable for this time of the year.”

Thorsten Petri, head groundsman of Schalke 04, is proud of this achievement. “In the past, the grass would not grow at all during the winter period. That is why we brought in artificial help, and it is evident that this has paid off.” According to Petri, he now uses 200 kg fertilisers, as the grass experiences a growing season throughout the year. This has also affected the cutting frequency. “We cut the grass three to six times a week, depending on the time of the year. Every so often, we do some top-dressing and aeration with hollow pins which we follow up by adding 70 to 100 tonnes of sand to the pitch.” The improved growing conditions also mean he and his team of seven now overseed regularly. “We overseed every four to six weeks.”

Integrated grass management

Its not just light that the Rhenac technology can add to the pitch. “Integrated grass management means balancing light, heat, ventilation and water. Our LED technology is very flexible and goes way beyond the on/off technology we know from HPS technology,” Horst Theisen of Rhenac Sports LED continues. Studies have shown that, where HPS technology achieves a 31% increasing in branching of the plant, the Rhenac LED technology achieves a 178% increase. “Different wave lengths have different functions. One of the advantages of our technology is that it provides the complete light spectrum. This allows us to deliver the light and light intensity required during the germination period or to facilitate grass growth or the grass to branch out as well as to improve its shear resistance at other times of the year.” Rhenac is currently busy finalising its automated field analysing capacity that will allow the grow lights to interact with the irrigation and field heating technology as well as industrial sized blowers that can cool down the temperature and bring more oxygen in. At present, it only communicates with sensors in the field. However, the trusses that hold the LED units have been fitted with heating equipment. “A side-effect of the HPS technology is that it produces heat. Often, this is more than the grass can handle. LED technology doesn’t have this side-effect, hence we also supplement heat when needed. The good thing is that LED light can be used without fearing the grass will be affected by heat, as LED luminaires don’t produce as much compared to HPS technology.”

Steel structure

The LED luminaires are fitted on two steel beams that span the field once rolled outside the venue. Each beam weighs approximately 190 tonnes and can be adjusted in height. “We had to do this as, on match day, this space is used as parking space for busses. We had to make sure they would still fit,” RSI SPORTS managing partner Arnoud Fiolet explains. RSI SPORTS has the sole marketing rights to the Rhenac Sports LED technology.

The two main trusses each have 24 automatically retractable B-beams that hold 60 LED spotlights each. “It boils down to light per square metre ratio. That is why we use one LED luminaire for every square metre pitch,” Theisen adds. It takes 12 minutes to fully employ the system. “Daylight reproduction capacity means machinery and software as well as a thorough understanding of the relationship between light spectra and grass growth and the relationship with other growth. Most importantly, it requires the objectification and digitalisation of natural turf quality and the ability to monitor this,” Fiolet points out. Rhenac Sports LED has packaged this in the R-BL-1750 installed at the Veltins Arena but also in smaller mobile units. “Our portfolio also includes the RML-30 that can cover 120-150 sqm a week, the RML-100 that covers 400-500 sqm a week, and the RML-200 that covers 800-1000 sqm a week. These units are ideal for just supporting the goal mouth area or supplementing light on sections of the field, like in front of the main stand that experiences shade regularly. The RML-200 is ideal for assisting a bigger portion of the field.”

Up for an award

According to the regulations by the German FA, the condition of a field is assessed four times per season. “Most of the time this is done by the grounds manager themselves but all data is submitted to a central database from where the developments are being monitored,” Nonn says. Each year, the grounds managers of the top three best-performing pitches receive an award to acknowledge their input. The field of the Veltins Arena has now jumped up the ladder. “We are pushing hard to be in that top-three,” an elated Petri admits. “That would be the first time in history for our venue.”

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Guy Oldenkotte

Guy Oldenkotte is senior editor of sportsfields.info and has been covering the outdoor sports flooring market and industry since 2003

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