Hybrid grass or reinforced natural grass is a product created by combining natural grass with synthetic reinforcing fibres. It is used for stadium pitches and training pitches, used for association football, rugby, American football, golf and baseball. Reinforced natural grass can also be used for events and concerts. The synthetic fibres incorporated into the rootzone make the grass stronger and more resistant to damage.
A first generation of hybrid grass appeared in the 1990s. Grass roots were allowed to intertwine with a mix of sand and synthetic fibres as they grew. Three main methods exist to insert synthetic fibres in the root zone. The first is to inject fibres in the sand with a tufting machine. This is the method used to create GrassMaster.
The second method is to mix fibres and sand in an automated plant and to install it afterwards on the pitch: this process is known as Fibresand.
The third method is to put a mat with woven or tufted fibres on the surface, to brush in sand or sand mixes afterwards to keep the fibres in an upright position and to seed grass mixtures finally. The natural grass roots through the mat and stabilizes the system.
Some of the older hybrid grass pitches were harder than unreinforced natural grass. This created concerns about the risk of injuries for players and maintenance for groundskeepers. Because of this, the sub base composition for hybrid systems evolved over time. It now often combines the following elements: sand, which is the main component of the rootzone; synthetic fibres, to reinforce the pitch; and an additional element to enable softness.
There are multiple patented technologies that concern hybrid grass, such as the following examples: XtraGrass developed by Greenfields b.v., SISGrass, developed by SIS Pitches. The latter uses a specific technology to inject polyethylene fibres into the soil, AirFibr, a technology developed by Natural Grass, which uses natural cork as the softness element, and Fibrelastic, developed by Mansfield Sand, which uses elastane fibres as the softness element. and GrassMaster, developed by Desso, obtained a patent on hybrid grass system based on injected fibres.