Technical Information - Irrigation
After sowing, it is essential that the soil surface is continually moist using the finest of mist sprinklers - heavy watering may cause run-off and wash away some of the seed resulting in patchy growth.
Water twice a day to ensure that the soil does not dry out. Some grasses. As the grass grows, reduce watering first to once a day (about the second week), then to every second day (about the third week).
Twice a week should be ample by the end of the first month with a once a week soaking after three months except in very hot and drying weather or on very light sandy soils.