Allow 3 to 5 days before sowing the area to ensure dust from the fertiliser granules and the granules themselves are at least partially dissolved into the soil helping avoid any root damage and/or stems of emerging seedlings. Should the seedbed be particularly dry wait 3 to 5 days after significant rainfall or irrigate the area well 3 to 5 days before sowing.
Applying, Battersby 6-9-6 Pre Seed Fertilizer at exactly the same time as seeding grass mixtures can be successful but does carry some risk, especially if the seedbed is dry at the time of sowing and light rainfall occurs as the grass begins to germinate. This is far less of a concern with mid to late autumn sowings.