Types of Playing Fields

Natural, reinforced, natural hybrid, synthetic hybrid, or synthetic. According to FIFA, there are 5 types of fields developed in recent years, but let's delve into more specifics and explore the true advantages between them.

Summary

The virtues of natural grass with synthetic reinforcement

In the quest for increasingly high-performing surfaces, during times when stadiums are used multiple times a week and offer difficult conditions for natural grass growth, several innovations have entered the market. Besides traditional natural grass and the established third generation of artificial grass, a new generation of playing surfaces—often simply referred to as hybrid systems—includes various combinations of materials and construction types. Following the document produced by FIFA, we will offer an overview of the different types of sports surfaces used in soccer, with some guidelines on technical aspects and performance, also in relation to the innovative hybrid system POWERgrass.

The Types of Playing Fields According to FIFA

Since many different terms are used to qualify surfaces as "hybrid," "reinforced," "mixed," the following table aims to provide a clearer overview of the different categories, placing them within the natural-synthetic continuum. The table is intended as a generalization of current products. With the evolution of innovations and technologies, updating classifications might become necessary. In 2017, FIFA proposed the following classification:

Playing field classification - FIFA 2017

Differentiation is based on the organic/inorganic nature of the materials used, the impact of the materials on the final product, and the typical maintenance required for each category. Natural grass is a living organism that can grow and regenerate, whereas synthetic grass does not.

1. The category "natural turfgrass" includes all cultivated or laid grass surfaces that do not include other materials.
2. "Reinforced surfaces" include additional support in the construction of the root zone, aiming to strengthen the grass hold. For the user, the surface does not appear different, as it is essentially just natural grass.
3. "Natural hybrid surfaces" are the ones most commonly referred to when using the term "hybrid." These are natural surfaces grown within a base of synthetic fibers. The synthetic fibers are visible but typically constitute less than 5% of the total grass coverage, which is why these surfaces are classified as "natural."
4. "Synthetic hybrid surfaces" are based on an artificial turf with sand but can use natural organic materials as the so-called performance infill (typically instead of rubber infill). This category is considered synthetic turf as it essentially requires the maintenance of an artificial grass field.
5. "Synthetic surfaces" are made of artificial materials (manufactured or fabricated by humans), typically a synthetic turf carpet, sand infill, and rubber infill with the possible addition of an elastic shock pad base.

Note: For certification purposes, hybrid grass systems belong to the natural grass field category.

The Substantial Differences Between Hybrid Systems

With the development of innovative technologies, further classification is possible as the choice between various hybrid systems and the installation method can significantly impact the field's usability during the week, construction and maintenance costs, and the possibility of renewing the system multiple times, thus its longevity. For example, among a vertically injected hybrid system in situ, a horizontally transplanted hybrid system in turf roll, and a horizontally installed hybrid system in situ, there are so many variables that can easily constitute three subtypes of natural hybrid fields.

the differences between hybrid systems

3.1 In the case of the natural vertical hybrid system, there is no support for the roots to cling to. The system requires a special machine for installation, and the fiber's hold to the ground depends on the consistency of the sand layer and the working depth. Usually, fibers are planted at 18 cm depth and form a very solid surface. During play, fewer holes form on the surface, but the ground tends to harden quickly. Post-match restoration and frequent aeration are still necessary to maintain the surface softness within the optimal range of 65-85g using the Clegg hammer. The difference between one vertical system and another is given by the quality of the fibers and their number per square meter, usually around 2500 points per square meter.

3.2 In the case of the natural horizontal hybrid system, it includes all types made with artificial carpets with an open horizontal backing, easily penetrable by roots anchoring into it. The fibers must be welded to the horizontal backing in the factory with a strength greater than 30 N. The difference between one system and another concerns the type of backing, the quality of fibers, and the number per square meter, which should not exceed 5% of the surface, to leave ample space for natural grass. We won't go into technical details between one system and another, but we can make a big distinction for those transplanted in the field in large turf rolls. This type of installation necessarily involves a nursery growing period between three to six months. Often, hybrid turf rolls are grown far from the final installation field, which entails adapting to a different climate. In any case, special machinery, numerous vehicles, and precise organization are required for the harvesting, transport, and laying of hybrid turf rolls. Additionally, transplantation is a significant stress for the lawn, creating more thatch, while differences between turf roll joints often require reseeding and sanding that tends to bury the synthetic fibers. During the natural grass renewal phase (necessary at most every 3 years), the operation is complicated, if not impossible, to remove natural grass without lifting artificial grass or damaging synthetic fibers.

3.3 In the case of the natural horizontal hybrid system with in situ installation, however, these issues are less pronounced because the artificial grass rolls with open backing are sewn together. Many believe that the lawn needs to grow for at least 6 months to reach the right maturity. However, thanks to an optimized cultivation method, it is possible to provide a horizontal hybrid turf ready for use within 4 weeks of sowing, a period consistent with the summer game break. In the case of fields with intensive use, prioritizing systems with a higher number of fibers, it is possible to have a field always playable even during winter, then plan reseeding in the optimal growing season. The stitching of rolls together allows for easy system renewal every 2 or 3 years without damaging the fibers or lifting the artificial grass, thus providing a field that can last over 20 years, like the POWERgrass field.

4.1 and 4.2 In the case of synthetic hybrid and synthetic refill hybrid systems, it should be clarified that in neither case do we have natural grass, except when weeds grow. The main difference between one and the other is that the former has two types of infills: the stabilizing infill (dried sand) and the infill with natural organic grains. Both infills must be removed when replacing the system at the end of its life cycle and possibly recycled for other uses. The synthetic refill hybrid system, on the other hand, does not use sand to stabilize the artificial turf because the performance infill is heavy enough to perform both functions. In this case, the infill can be partially reworked, cleaned, and reused at the end of the artificial grass's life cycle.