Good grass is crucial for playing football or golf, but it has more to it than you might expect. In recent years, soil scientist Evers has seen increasing problems with controlling carbon accumulation in the top layer (the top 1-2 centimetres) of a lawn. ‘The carbon enters the soil via living and dead grass roots, forming a thick layer of felt. Soil life often cannot process carbon fast enough and the soil deteriorates due to the carbon surplus. This causes the grass to deteriorate: it is less resistant to trampling and gets sick more quickly.’ Intensive maintenance can help the turf and the soil, but in the context of sustainable management, it is best avoided. ‘It costs a lot of time and money, and it is better for the soil if it can solve these kinds of problems itself.'
Rainfall peaks
It is not only footballers who benefit from good-quality turf: sports fields play an important role during heavy rainfall. Evers: ‘When there is a sudden downpour, we increasingly see that the water has difficulty draining away. On plots of land where the top layer of the turf is full of carbon that has been turned to felt, the water does not drain away properly and flooding occurs. But when there is grass that does not smother the soil and through which rainwater can easily pass, it helps with water buffering.' This may also play a bigger role in the future in cities. 'Grass in parks, for example, through which water can drain properly, will become increasingly important for the drainage of excess rainwater.'
Root flushing
The soil scientist examined various types of grass and investigated how much carbon they accumulated in different layers of the soil. He scooped hundreds of small pieces of grass with a diameter of about 3 centimetres and washed out the roots in the greenhouses of Radboud University. These roots were tested for carbon-nitrogen ratio, among other things. Evers: ‘We saw significant differences between various types of grass. Unlike smooth-stalked meadow grass, perennial ryegrass accumulates relatively little carbon at the top of the soil and is very suitable for sports fields and golf courses. It requires little maintenance and also helps drain rainwater. For golf courses and parks, red fescue with runners is also a very wise choice.'
There really is a lot to choose from, says the soil scientist: ‘The right grass requires little maintenance, ensures the right balance in the soil and helps with precipitation peaks.'