Why sand?
Sand is a commonly used additive in soils intended to support grass. A golf green, for example, is often made up of over 90% sand.
What is the point of sand on the lawn?
Sand increases the pore size in the soil and thereby improves the movement of water and air at the roots. Depending on which sand I use, this also influences the pH value, the water retention capacity and the cation exchange capacity of the soil. This determines how well nutrients, for example from fertilizers, can be stored in the soil and released again for the roots.