A coarser top dressing is laid over the seeds. Water Works Wonders Water passes down through the top dressing and seeks its lowest level, wetting the seeds as it passes. The top dressing protects the wet seeds from being dried out by sun and wind. Water rises through the undisturbed soil and reaches the level of the seeds where it stops. The top dressing, being coarser, won't support further rise so water collects at the boundary between the soil and top dressing where the seeds are.
Germination is enhanced and the plants get a healthy start.
Balance Moisture balance is necessary for proper germination. Lots of water may not be enough if it doesn't reach the seeds. Regular watering that replaces water runoff and evaporation will assure a good start for lawns, turfgrass or any other planting.