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Förstärkning av naturligt gräs

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The innovative hybrid turf PowerGrass against older generation hybrid system: definition and comparison of the limitations and advantages.

The request for hybrid turf is increasing so it is good to provide a clear definition and differentiate hybrid turf systems from natural grass reinforced.

Analyzing the etymology of the words it is understood that for natural grass reinforced means: "the set of methods that use synthetic products to reinforce the natural grass".

Actually there are available in the market microfibers, elastic fibers, small nets mixed in the sand based rootzone, synthetic green fibers implanted into the sand based growth medium that protrude on the surface and even synthetic turf integrated into the sand based rootzone.

Within the category of natural grass reinforced, there are also synthetic turf fabrics that are installed over a sand based rootzone and filled in with sand based rootzone where grass grows naturally in the space between the synthetic fibers. In most cases, those kind of syntethic turf comprise a support (backing) specially designed that, at least from a theoretical point of view, the roots should penetrate and grow also in the sand based medium under the backing. In a nutshell, the natural grass is meant to grow and thrives within a synthetic turf.

Many define those mixed grass as "hybrid turf", because the synthetic turf looks green just like natural grass, but it is good to take a step forward to a better understanding of what is really about. Analyzing the etymology of the word hybrid, from the agronomic point of vew, this term is improper because otherwise there had to be a genetic "fusion" and this is impossible. Therefore, considering the mutual benefits that these systems offer between natural grass and artificial turf, we can define that is about a sinergy so it would be fair to provide a definition of "sinergic turf" or "combination turf".

However, taking a cue from the automotive industry is conventionally accepted the term "hybrid" for a car powered by two different energy sources such as gasoline and electricity. Taking a parallelism in the sports fields we can define a "hybrid turf" or "hybrid grass" a mixed grass, natural and synthetic, where is possible to play either with or without the natural grass.

This also coincides with the market demand and it is the concern of many who use the playing field so extreme. In little substance, setting a new market standard we can define that hybrid turf system in that provides proper conditions for natural grass growth from the very beginning and playable field even in those cases that, for any reason (extreme use, weather conditions or human mistake), the natural grass could be possibly damaged.

PowerGrass hybrid turf has innovative features and offers playing conditions and better growth than any other system of reinforced natural grass or old type hybrid grass and at the same time is the only one that offers a sports field playable even without the natural grass. The synthetic turf is stable and the natural grass can be easily installed with simple seeding.

The reinforcement of natural grass is not so simple, first of all you have to respect the rules of nature.

Hybrid turf systems are not new. The first hybrid grass was developed in the United States in 1993. It seemed like a brilliant idea, but had limited success for the following reasons:

  1. difficulties in producing a functional fabric to achieve the targets
    • it was particularly difficult to fix the synthetic fibers to the support (backing). Roots provide support to the turfgrass, they absorb water and nutrients in the soil. To perform their function both roots and bacteria, useful to mineralize the nutrients, need oxygen to breathe. Having to breathe the roots and stimulate their development even under the backing, it is not possible to use the classic fabric (closed) in PP coated with latex or PU, which is necessary to fix the fibers to the support. The industry has applied an open tissue (geonet) and tried to lock up the fibers by applying a second support biodegradable, which over time would decompose to permit the roots to penetrate the fabric (geonet) and grow also below the backing, in the background growth medium. Experience showed up that degradation does not occur on time compatible with the needs of the grass, because it depends on many factors, physical and environmental, and the grass establishment is not easy, but what is more important,
    • the lock up of the fibers is weak from the very beginning and by time the degradation of the second support loosens completely the fastening of the fibers to the backing. Natural grass simply remains anchored to the geonet, but the artificial fibers do not contribute to the stability of the playing surface. When the natural grass is weak, or worn, it gives away and together with the grass sods the artificial fibers are removed as well, uncovering the backing, therefore reconstruction is necessary.
      Few, even today, promote a fabric with an open backing (geonet) without using the second support to fix the fibers to the geonet. The artificial grass produced in this way is incomplete, not suitable, as it is not possible even to infill the filling material and brush up the fibers that should protrude at least 1-2 cm above the growth medium. We often observe that fibers are buried in the growth medium and they do not perform any reinforcement or protection on the grass crown and the stability of the growth medium. In this case the only reinforcement is the fact that the roots can be anchored on the geonet.
  2. unfavorable growth conditions of natural grass:
    • during the first period of growth, the roots do not penetrate the fabric until it degrades, meanwhile they grow above the backing increasing the thatch layer. A shallow growth medium needs frequent irrigation, consequently the roots remain "comfortable" in the surface above the backing. It's known that turfgrass in these conditions is not resistant to any environmental stress or intensive use,
    • in some cases the excess of moisture associated with a rich biological activity consumes oxygen (O2) in the soil, giving rise to an anaerobic activity that consumes the little oxygen left from the water (H2O) and oxides of sulfur (SO2 and SO3) thereby releasing hydrogen (H) and elemental sulfur (S). Those two elements form a very powerful acid, a toxic poison, the hydrogen sulphide (H2S) with a characteristic smell of rotten eggs. The persistence of these conditions results in a fatal poisoning of the grass that becomes red, rootless and dies.
    • some producers fix the fibers applying liquid adhesive over the entire surface or in large part of the support with one of the classic methods for the artificial turf (latex, polyurethane, thermoplastic), then make a high number of holes to encourage the penetration of the roots. In fact, the roots do not pass, probably due to the fact that the number of holes is limited and because, in said backing, the space between the holes, is impermeable, so the water deposited above the backing forms a invisible water barrier, due to the surface tension of water blocking gas exchange, that reflects on non favorable growing conditions for the roots under the backing. Another possible explanation is the fact that the water deposited above the backing helps retain excess moisture in the rootzone above the backing, intensifying the phenomenon of intoxication with the formation of hydrogen sulphide (H2S).
  3. playing surface very hard:
    • over the years, the industry has always tried to built a hybrid grass with syntethic turf and sand according to the USGA indications. The sand offers a high porosity growth medium where roots can grow easily, but after a certain number of hours of play, even in sandy soils, the surface becomes hard and requires decompaction. With the introduction of synthetic fibers in the sand to increase stability, after the first period, the surface becomes even harder and requires decompaction more frequently. The presence of a hard fabric with weft and warp open tissue (geonet), often used to distribute the loads, at the first period works well, but form subsequently a very hard surface. If nothing is done, the lawn undergoes a hardening in the surface and tends to thin out.

PowerGrass® hybrid turf is not simply a product, it's a complete system

All details have been subject of reflection and a long study to understand the ideal characteristics of both synthetic turf and growth medium.

Following a long study and direct experience in the field that characterizes the partners involved in PowerGrass group we realized that it is crucial to develop an indivisible set of essential features to provide the ideal hybrid turf system by:

  1. the use of robust and resilient synthetic fibers to keep the standing position above the surface and truly protect the natural grass crowns;
  2. welding (tuft-lock) the artificial grass fibers to a breathable support without clogging its porosity is just a must in order to infill the synthetic turf with sand based growth substrate, by brushing and harrowing the fibers so that they protrude above the surface of 20-30 mm and protect the natural grass crowns; during the future maintenance is possible then to remove the thatch (by scarifying with springs) or all the natural grass (re-turfing) without damaging synthetic fibers;
  3. the use of a backing for synthetic turf, not biodegradable, open, with three-dimensional structure, thus breathable evenly across the surface; in details there are other aspects that characterize the synthetic turf backing, equally essential to provide an ideal system for professional games and for the natural grass growth, such as:
    • the backing must be soft and flexible at each intersection between the holes, to allow a better interaction of the cleat of the player with the hybrid turf and prevent hardening of the surface;
    • the backing must have high porosity for about 160,000 holes interconnected thanks to the three-dimensional structure that prevent water stagnation over the surface and allow gas exchange; at the same time, the size and shape of the holes is such as to a) allow the penetration of the roots from the beginning of the natural grass growth, then reinforce the anchorage of the turfgrass sods that dramatically increases the tear resistance caused by player's slide tackling and b) does not allow sand migration into the backing, to keep open and soft its interior structure;
    • finally, the backing must be ladder-proof thanks to its knotted fibers at every intersection so its texture will not come apart upon applied multiple solid tines perforation, necessary to till and aerate the sand growth medium below the backing.

All of these features provide the ideal fabric for an excellent hybrid system, quite unique in the world, protected by 3 international patent applications.

Geofill®, the ideal soil conditioner to get the best outcome from PowerGrass system

An excellent hybrid turf system also requires an ideal sand based growth medium to optimize sports performance and natural grass growing conditions and the development of the roots above and below the backing.

Geofill® is the result of a long reflection and intuition thanks to a deep knowledge of both worlds: that of natural grass and artificial turf.

Geofill® increases the porosity and moisture content of the sandy growth medium, provides its isolation proprieties to reduce extreme temperatures variations during hot summers and winter frost, attributes a cushioning effect to the playing surface and reduces soil compaction and the bulk density of the substrate.

The soil conditioner Geofill®, contains coco peat, gentle fine cork


and zeolite sand. Integrate in the growth medium Geofill® is just as important to enhance performance, resistancec, duration, reducing dramatically maintenance costs.

  • coco peat will restrain moisture and generate humus in the growth medium to provide carbon to microorganisms for long period;
  • zeolite sand will increase soil fertility by increasing CEC (Cation Exchange Capacity);
  • gentle fine cork is stable over 60% for about 100 years and is used to balance temperature and air/water content in the growth medium, reduce compaction and provide a softer playing surface;

PowerGrass hybrid turf with natural grassPowerGrass hybrid turf with natural grass

Natural grass in full growth on PowerGrass hybrid turf system covers the synthetic turf from UV sun rays.

PowerGrass hybrid turf without natural grassPowerGrass hybrid turf without natural grass

Natural grass in case on extreme use, weather conditions or human mistake is possible to give away. In this case the synthetic turf of the hybrid turf system PowerGrass emerge to offer continuity of play until the next sowing for the regeneration of natural grass.

Förstärkning av naturligt gräs

Observe a direct comparison and the limits of another hybrid turf system: the fastening of synthetic fibers to the horizontal support is inadequate: when the natural grass gives away, even synthetic fibers are removed away from the player; moreover, if the fibers are "buried" in the sand based rootzone, do not offer protection to the grass crowns.

The synthetic fibers used on direct soil injected system (left) are of 100 microns, compared to hybrid turf PowerGrass (right) of 365 micronThe synthetic fibers used on direct soil injected system (left) are of 100 microns, compared to hybrid turf PowerGrass (right) of 365 micron

Only elastic fibers (on the right) maintain an upright position and protect the crowns of the plants of natural grass. Actually, PowerGrass hybrid turf is provided with 365 micron of synthetic fibers to ensure resilience and resistance to natural grass maintenance interventions.

Not breathable backing from the very beginning in this hybrid grass has no roots bellow the backing after several weeks from installationNot breathable backing from the very beginning in this hybrid grass has no roots bellow the backing after several weeks from installation

A strong limit of another old hybrid turf system: the roots do not penetrate the backing until the partial degradation of the backing takes place. When this happens, it affects approximately 1/3 of the surface of the support as the remaining 2/3 is waterproofed from the "finger coating" over the backing that welds the fibers in alternate rows to it. A strong limitation when only 8-10 weeks are available for the development of natural grass and even after as rooting affects only 1/3 of the surface, that may result limited from the water barrier.

Poor growth conditions of an hybrid grass not suitable, compared to natural grassPoor growth conditions of an hybrid grass not suitable, compared to natural grass

The synthetic turf should not prevent the growth of natural grass: in most of the older systems, we observed that the soil becomes very hard and suffocating the growth of natural grass.

Instead PowerGrass hybrid grass will provide better growth conditions and resist more compared to natural grassInstead PowerGrass hybrid grass will provide better growth conditions and resist more compared to natural grass

In PowerGrass the synthetic turf assists the growth of natural grass: the synthetic fibers provides shadow to grass shoots against the summer heat meanwhile the support of synthetic turf provides water content and preserve the heat in the growth medium against the winter cold.

The soil conditioner Geofill PG is the result of a long experimentationThe soil conditioner Geofill PG is the result of a long experimentation

After a long trial of all available organic amendments we came to the special blend of Geofill PG containing cork and coconut.

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