The best way to get your grass seed to establish roots and germinate in sandy soil is to prepare it first. This includes adding fertilizers or organic material to give your grass seeds a layer of amenable soil to begin their rooting process in, and get the nutrients they need. Because sandy soil dries out so quickly and doesn’t hold onto nutrients, adding extra materials is essential. These will retain water and allow the grass seeds to access nutrients for longer periods of time. This process is known as amending the sandy soil, through organic matter or fertilized topsoil. Add a layer of compost to your sandy soil, including humus, decomposed leaf matter, and grass clippings, to provide a plethora of nutrients for new grass seeds. Additionally, peat or vermiculite are good options for increasing the soil’s water retention.